http://physics.ucsd.edu/~jorge/hole.html
Electrodinamica de superconductores: una propuesta alternativa
Departamento de Teoria de la Materia Condensada,
Instituto de Ciencia de Materiales de Madrid, CSIC.
July 9, 2004.
Abstract:
Se asume generalmente que la electrodinamica macroscopica de superconductores esta descripta por las ecuaciones de London. Estas ecuaciones no permiten la presencia de campos electricos en superconductores. Nosotros proponemos una descripcion alternativa de la electrodinamica de superconductores, que surge de la teoria microscopica de superconductividad por huecos. La nueva electrodinamica tiene covariancia relativista y permite la presencia de campos electricos en superconductores. En esta descripcion, superconductores se entienden como 'atomos gigantes'. Discutimos algunas consecuencias experimentales de la teoria que permitirian decidir sobre su validez.
Electron-hole asymmetry and superconductivity
SNS2004,
Spectroscopies in Novel Superconductors,
Sitges, Spain, July 11-16, 2004
Abstract
(pdf)
The fundamental role of charge asymmetry in superconductivity
Temple University, February 7, 2005
Abstract:
Superconductivity occurs predominantly in materials where the charge carriers in the normal state are holes rather than electrons. Examples are high Tc cuprates, magnesium diboride, and the elemental superconductors. Other clear manifestations of charge asymmetry in superconductivity are asymmetric tunneling characteristic in cuprates and properties of rotating superconductors. However the importance of charge asymmetry for superconductivity has not been widely recognized: BCS theory of conventional superconductivity as well as new theories proposed to describe high Tc cuprates do not differentiate between electron and hole carriers. I will discuss an alternative theory of superconductivity that has charge asymmetry as its fundamental ingredient. The theory explains many experimental observations, including the remarkable Tao effect, makes testable predictions, and provides new guidelines for the search for new high Tc superconducting compounds.
Explanation of the Tao effect
2005 APS March Meeting,
Thursday, March 24, 2005
LACC - 507, 11:15 AM-11:27 AM
Abstract:
Tao and coworkers discovered that in an applied electric field superconducting microparticles aggregate to form balls of macroscopic dimensions$^{(1)}$. The phenomenon appears to be as general as the Meissner effect. Within the conventional theory of superconductivity electrostatic fields do not penetrate into superconductors and the observed effect would not be expected. We propose an explanation of the effect based on an alternative description of the electrodynamics of superconductors recently proposed$^{(2)}$, that results from the unconventional theory of `hole superconductivity'. In our theory a spontaneous electrostatic field exists inside superconductors and if the sample is not spherical also outside. Experiments to test the theory will be discussed. (1) R. Tao, X. Xu and E. Amr, Physica C 398, 78 (2003) and references therein. (2) J.E. Hirsch, Phys.Rev. B 69, 214515 (2004) and references therein.
Superconductors, Tao balls, and macroscopic atoms
San Diego State University, September 16, 2005
Abstract:
When Rongjia Tao recently applied an electric field to millions of superconducting microparticles in suspension he discovered a surprising new effect(1): they fly towards each other, clumping up into a tightly bound round ball of mm-size radius. Neither London nor BCS, the founders of the currently established understanding of superconductivity, expected this, nor do they have any clue as to why this occurs. To me, Tao balls look like giant atoms, and the phenomenon is a manifestation of the fundamental charge asymmetry of matter that is at the root of the phenomenon of superconductivity according to the unconventional theory of "hole superconductivity"(2). I will present the essential elements of this theory, developed over the past 15 years, describe how it explains the "Tao effect", and discuss other experiments that could be done to decide on its ultimate validity or invalidity.
(1) R. Tao, X. Xu and E. Amr, Physica C 398, 78 (2003) and references therein.
(2) J.E. Hirsch, Phys.Rev. Lett. 94, 187001 (2005) and references therein.
Alternative electrodynamic equations for superconductors:
theoretical and experimental implications
Concepts in Electron Correlation,
September 30th - October 5th 2005,
Hvar, Croatia
Abstract:
The theory of hole superconductivity(1) has been proposed as an alternative to the
conventional theory of superconductivity to describe both high Tc and conventional
superconductors. It has many elements in common with the conventional London-
BCS theory as well as profound differences. In particular,
the macroscopic electrodynamic equations governing superconductors are predicted to be different in the new
theory, which leads to prediction of unexpected effects: penetration of electric fields
into superconductors, spontaneous electric fields around superconductors, spherical
aggregation of superconducting microparticles in an electric field (Tao effect), spin
currents in the ground state of superconductors, changes in the plasmon dispersion
relation. These predictions are experimentally testable. Other new and unexpected
effects will be discussed.
(1) References in http://physics.ucsd.edu/ jorge/hole.html
Why are Physicists Silent? The Dangers of New US Nuclear Weapons Policies
94th STATISTICAL MECHANICS CONFERENCE, Rutgers University, December 19, 2005
Electric Fields in Superconductors: an Explanation of the Tao Effect
94th STATISTICAL MECHANICS CONFERENCE, Rutgers University, December 19, 2005
Abstract:
When Rongjia Tao recently applied an electric field to millions
of superconducting microparticles in suspension he discovered a
surprising new effect(1): they fly towards each other, clumping up
into a tightly bound round ball of mm-size radius. Within the
conventional theory of superconductivity electrostatic fields do
not penetrate into superconductors and the observed effect would not
be expected. I propose an explanation of the effect based on an
alternative description of the electrodynamics of superconductors
that results from the unconventional theory of `hole superconductivity'
(2).
(1) R. Tao et al, Phys. Rev. Lett. 83, 5575-5578 (1999)
(2) References in J.E. Hirsch, http://physics.ucsd.edu/~jorge/hole.html
What the h-index is and why it matters
Allen Press Emerging Trends Seminar, April 26th, 2006, National Press Club, Washington DC
Do superconductors violate basic laws of physics?
San Diego State University, September 15, 2006
Abstract:
I will show that superconductors violate at least one basic law of
physics: either Lenz's law, or angular momentum conservation, or Newton's
second law. For those that have faith in theory I will explain how this
conundrum can be resolved with least collateral damage. For those
that don't I will discuss a simple experiment that can decide between the
different possibilities, that could have been done many years ago but hasn't.
Nucleoholic and dangerous: the US and its nuclear weapons
Osher Lifelong Learning Institute, UCSD, October 5, 2006
Abstract:
Like a recovering alcoholic, the US has been nuclear-sober for 60 years.
However, changes in the US nuclear weapons policies under the Bush
administration, characterized as "a radical departure from the past" by Linton
Brooks, the chief US administrator of the nuclear weapons arsenal, are bringing
us dangerously close to relapse. I will discuss the rationale as well as the
irrationality and enormous danger entailed in the new US nuclear policies and
plans, and why they may be put into practice in a confrontation with
Iran. I will also discuss why non-proliferation initiatives and efforts for
reduction and ultimate elimination of nuclear weapons arsenals increase
rather than reduce the danger, and what should be done instead.
On a new effect observed in the transition to the supraconductive state
Fritz Haber Institute, Berlin, March 23, 1937 2007
Abstract:
Professor Walther Meissner and Herr Dr. Robert Ochsenfeld in Berlin
recently discovered a new effect in supraconductors: the magnetic
field intensity in the neighborhood of a supraconducting body changes
when the body is cooled in an external magnetic field. This surprising
effect appears to violate the Maxwellian theory of electromagnetism as
well as the conservation of angular momentum required by Newtonian
theory. However I will propose an explanation of Meissner's observation
that is consistent with Maxwellian and Newtonian theory. This
explanation requires that spontaneous electric fields exist inside
supraconductors in the absence of externally applied fields. Theoretical
and experimental evidence in favor of this strange hypothesis will
be presented, and new experiments will be proposed to test its validity.
The h-index: how useful is it as a measure of scientific achievement?
DPG Meeting, Regensburg, Germany, March 26-30, 2007
Abstract:
The h-index was proposed in 2005 as a succinct way to quantify
an individual's scientific research output. It has generated
considerable interest not only in physics but also in other scientific
disciplines, and has recently been implemented in the ISI Web of Science.
Several extensions of the original concept have also been proposed. I will
discuss various properties of the h-index, what I view as its advantages
over other indicators and potential disadvantages, and whether it is a
good predictor of future achievement.
Will the U.S. Use Nuclear Weapons in a Military
Confrontation with Iran? Why Congress Needs to
Confront This Possibility
GROSSMONT COLLEGE POLITICAL ECONOMY WEEK, APRIL 30-MAY 4, 2007,
San Diego, California
How hole conductors become electron superconductors
High-Temperature Superconductivity in Cuprates,
Original Concept and New Developments, October 7 - 12, 2007
Tbilisi, Georgia
Abstract:
Holes dominate the normal state transport in high Tc hole-doped cuprates,
in electron-doped cuprates in the regime where they become
superconducting(1), in the relatively high Tc MgB2, and in the vast
majority of "conventional" superconductors. Electrons carry the
electric current in the superconducting state of those
materials (as revealed by London moment measurement and other experiments)
and in the normal state of materials that never become superconducting
such as alkali and noble metals. The discovery of high Tc superconductivity
in cuprates by Bednorz and Muller and subsequent developments shone a
bright light into the key role of charge asymmetry in superconductivity
generally, which had escaped attention before. The theory of hole
superconductivity(2) is proposed to apply to all superconducting materials
and explains those as well as many other observations such as asymmetric
tunneling spectra(3) and optical spectral weight transfer. It proposes
that superconductivity originates in pairing and condensation of
electron-hole-asymmetric electronic polarons, driven by kinetic energy
lowering. A new class of model Hamiltonians grounded in basic ubiquitous
atomic physics, "dynamic Hubbard models", describes the microscopic physics.
The theory predicts a novel inhomogeneous charge distribution in superconductors, with excess negative charge near the surface.
With respect to "At the extreme forefront of research in superconductivity
is the empirical search for new materials" the theory dictates that the
search for high Tc superconductivity should be restricted to materials
where normal state transport occurs in negatively charged
substructures (eg planes) with closely spaced anions and almost filled
energy bands.
(1)Y. Dagan and R.L. Greene, " Hole superconductivity in the electron-doped superconductor Pr2-xCexCuO4", Phys.Rev. B76, 024506 (2007).
(2)References in: http://physics.ucsd.edu/~jorge/hole.html
(3) F. Marsiglio and J.E. Hirsch, "Tunneling asymmetry: A test of superconductivity mechanisms", Physica C 159, 157 (1989); P.W. Anderson and N.P. Ong, "Theory of asymmetric tunneling in the cuprate superconductors", J. Phys. Chem. Solids 67, 1 (2006).
The Meissner Effect, the Tao Effect, and Other Unexplained Riddles of Superconductors
UCSD Physics Colloquium, January 24th, 2008
Abstract:
The Meissner effect, discovered in 1933, is the process by which a superconductor expels a magnetic field from its interior as it makes the transition from the normal to the superconducting state. It is a hallmark of superconductivity. It is generally believed that the Meissner effect is throughly explained by theory: phenomenologically by London's 1935 theory and microscopically by BCS (1957) theory. Instead, I will try to convince you that the Meissner effect is a fundamental unexplained riddle within conventional London-BCS theory. Another unexplained effect that occurs when strong electric fields are applied to superconductors was discovered by Rongjia Tao in 1999. Finally, many more unsolved riddles resulted from the 1986 discovery of high temperature superconductivity in cuprate oxides. I will discuss the basic principles of the unconventional theory of hole superconductivity, proposed to describe both high temperature superconductivity in cuprates as well as superconductivity of conventional materials. The theory offers an explanation for the Meissner effect and the Tao effect, and predicts a new as yet unseen physical phenomenon in all superconductors, the "Spin Meissner effect".
Spin Meissner Effect in Superconductors and the Origin of the Meissner Effect
Link to talk here
Conference on Concepts in Electron Correlation
September 24 - 30, 2008 Hvar, Croatia
Abstract:
The expulsion of magnetic flux from the interior of a metal that becomes superconducting
(Meissner effect) was discovered experimentally in 1933. Contrary to conventional
wisdom, I argue that it is impossible to explain this effect within the accepted framework of
London-BCS theory: one would have to assume either violation of Lenz's law, or violation
of angular momentum conservation, or both. Instead, I propose that the outward motion of
magnetic field lines as a metal goes superconducting reflects and is a consequence of outward
motion of electric charge, just like would happen in a classical plasma (Alfven's theorem).
According to the theory of hole superconductivity[1], metals become superconducting because
they are driven to expel excess negative charge from their interior. This is why high
Tc occurs in the highly negatively charged (CuO2)=, B- and (FeAs)- planes of cuprates,
MgB2 and iron arsenides respectively, and why NIS tunneling spectra are asymmetric, with
larger current for a negatively biased sample. How to reconcile the resulting macroscopic
charge inhomogeneity with the supposed non-existence of macroscopic electric fields in the
interior of superconductors will be discussed in the talk. Charge expulsion is also associated
with an expansion of the electronic wavefunction and a decrease in the kinetic energy associated
with quantum confinement, consistent with observations[2]. In addition to explaining
the Meissner effect, this physics gives rise to a Spin-Meissner effect[3]: a macroscopic spin
current is predicted to flow near the surface of superconductors in the absence of applied
external fields, of magnitude equal (in the appropriate units) to the critical charge current
of the superconductor. The orbital angular momentum of each electron in the spin
current equals its spin angular momentum. This physics also provides a geometric interpretation
of the difference between type I and type II superconductors, and predicts that
the macroscopic electric field in the interior of superconductors equals the thermodynamic
critical magnetic field Hc or Hc1 for type I and type II superconductors respectively. These
predictions are theoretically and experimentally testable.
[1] References in http://physics.ucsd.edu/ jorge/hole.html
[2] H. J. A. Molegraaf et al, Science 295, 2239 (2002).
[3] J.E. Hirsch, Europhys. Lett. 81, 67003 (2008); Ann. Phys. (Berlin) 17, 380 (2008).
Charge expulsion, Spin Meissner effect, and charge inhomogeneity in superconductors
Second CoMePhS Workshop in
Controlling Phase Separation in Electronic Systems,
Nafplion, Greece - September 30th - October 4th 2008
Abstract:
Superconductivity occurs in systems that have a lot of negative charge: the
highly negatively charged (CuO2)= planes in the cuprates, negatively charged (FeAs)-
planes in the iron arsenides, and negatively charged B- planes in magnesium
diboride. And, in the nearly filled (with negative electrons) bands of almost
all superconductors, as evidenced by their positive Hall coefficient in the
normal state. Why? No explanation for this charge asymmetry is provided by
the conventional theory of superconductivity, within which the sign of electric
charge plays no role. Instead, the sign of the charge carriers plays a key
role in the theory of hole superconductivity[1], according to which metals
become superconducting because they are driven to expel negative charge (electrons)
from their interior. This is why NIS tunneling spectra are asymmetric, with larger
current for negatively biased samples, as was predicted by this theory[2] long
before it was experimentally verified[3]. The theory also explains the (otherwise
unexplained[4]) Meissner effect: as electrons are expelled towards the surface in
the presence of a magnetic field, the Lorentz force imparts them with azimuthal
velocity, thus generating the surface Meissner current that screens the interior
magnetic field. In type II superconductors, the Lorentz force acting on
expelled electrons that don't reach the surface gives rise to the azimuthal
velocity of the vortex currents. In the absence of applied magnetic field,
expelled electrons still acquire azimuthal velocity, due to the spin-orbit
interaction, in opposite direction for spin-up and spin-down electrons: the "Spin
Meissner effect"[5]. This results in a macroscopic spin current flowing near the
surface of superconductors in the absence of applied fields, of magnitude equal to
the critical charge current. Charge expulsion also gives rise to an interior
electric field and to excess negative charge near the surface. In strongly type II
superconductors this physics should give rise to charge inhomogeneity and spin
currents throughout the interior of the superconductor, to large sensitivity
to (non-magnetic) disorder and to a strong tendency to phase separation.
References
[1] References in http://physics.ucsd.edu/~jorge/hole.html.
[2] F. Marsiglio and J.E. Hirsch, "Tunneling Asymmetry: a Test of Superconductivity Mechanisms", Physica C 159, 157 (1989).
[3] Y. Kohsaka et al, Science 315, 1380 (2007).
[4] J.E. Hirsch, J. Phys. Cond. Matt. 20, 235233 (2008).
[5] J.E. Hirsch, Europhys. Lett. 81, 67003 (2008); Ann. Phys. (Berlin) 17, 380 (2008).
Meissner effect and Spin Meissner effect in superconductors
XIV Simposio en Ciencia de Materiales
Centro de Nanociencias y Nanotecnologia
Universidad Nacional Autonoma de Mexico
Ensenada, Baja California,
Mexico, Febrero 10-13, 2009
Abstract:
The Meissner effect is the spontaneous generation of a surface charge current in a metal that makes a transition from the normal to the superconducting state in the presence of an external magnetic field. It was discovered experimentally in 1933 and supposedly explained by BCS-London theory by 1957. I will argue that the Meissner effect is not explained by conventional BCS-London theory, hence it remains an outstanding puzzle calling for an explanation. Another outstanding puzzle is the origin of high temperature superconductivity in cuprate oxides discovered in 1986 by Bednorz and Muller. I will discuss the basic principles of the unconventional ``theory of hole superconductivity'' that is proposed to apply to all superconductors and (i) explains the puzzle of high Tc superconductors, (ii) explains the origin of the Meissner effect, and (iii) predicts a new as yet undetected effect in superconductors, the ``Spin Meissner effect'': the spontaneous generation of a surface spin current in a metal that makes a transition from the normal to the superconducting state in the absence
of external fields, resulting in the existence of a surface spin current in the ground state of superconductors.
h index and hbar index
NSF workshop on "Scholarly Evaluation Metrics: Opportunities and
Challenges", Washington DC, December 16th, 2009
Abstract: The h index and the hbar index were discussed.
h is the number of papers of an individual that have citation count
larger than or equal to the h of that individual
hbar is the number of papers of an individual that have citation count
larger than or equal to the hbar of each of the coauthors of each paper
Explanation of the Meissner Effect and Prediction of a Spin Meissner Effect in Superconductors
UCLA condensed matter seminar, January 20th, 2010
Abstract:
When a metal is cooled into the superconducting state in the presence of a static external magnetic field, a surface current starts flowing spontaneously that creates a magnetic field equal and opposite to the applied magnetic field in the interior of the body (Meissner effect). What is the force that generates this surface current, and how can it overcome Faraday's electric force that opposes it? How is angular momentum conserved? I argue that the conventional BCS-London theory of superconductivity cannot answer these questions.
I propose an explanation of the Meissner effect that requires new electrodynamic equations for superconductors, that are symmetric in electric and magnetic fields. These equations predict the existence of a spontaneous electric field in the interior of superconductors and the generation of a surface spin current when a metal is cooled into the superconducting state in the presence or absence of an external magnetic field. I call this the "Spin Meissner Effect" and predict that it is a universal property of all superconductors. The speed of the carriers of the spin current is hbar/(4 x electron mass x London penetration depth).
I discuss the relation of this physics to the theory of `hole superconductivity', to what extent it is supported or contradicted by existing experiments, and how it furnishes criteria that can help find new higher temperature superconductors.
Charge expulsion and Spin Meissner Effect in Superconductors
APS March meeting, Portland, Oregon, March 2010
(Link to abstract here)
Abstract:
I argue that the Meissner effect (expulsion of magnetic field from the interior of a metal going into the superconducting state) cannot be explained by the conventional BCS-London theory, hence that BCS-London theory is incorrect[1]. The theory of hole superconductivity explains the Meissner effect as arising from the expulsion of negative charge from the interior of the superconductor towards the surface, resulting in a non-homogeneous charge distribution, a macroscopic electric field in the interior, and a spin current near the surface (Spin Meissner effect). Electrodynamic equations describing this scenario will be discussed[2]. In the charge sector, these equations are related to electrodynamic equations originally proposed by the London brothers[3] but shortly thereafter discarded by them[4]. [1] J.E. Hirsch, Physica Scripta 80, 035702 (2009). [2] J.E. Hirsch, Ann. Phys. (Berlin) 17, 380 (2008). [3] F. London and H. London, Proc. R. Soc. London A149, 71 (1935). [4] H. London, Proc. R. Soc. London A155, 102 (1936).
Superconductors as big atoms, and
atoms as small superconductors
UCSD Condensed Matter seminar, October 13th, 2010
Abstract:
According to Bohr's correspondence principle, microscopic quantum
behavior should smoothly morph into macroscopic classical behavior.
Superconductivity is a unique state of matter where quantum mechanics
manifests itself at a macroscopic scale. As such, it presents us with the
unique challenge to understand the same phenomenon from both a
quantum and a classical point of view. Together with this challenge
comes a unique opportunity: superconductors give us a `window' through
which we can peer into the microscopic world and understand it in a new
way. In this connection, I will discuss what the theory of hole
superconductivity can teach us about angular momentum, quantum phase,
quantum zero-point motion and double-valuedness of wavefunctions.
Instead, the conventional BCS-London theory of superconductivity ignores
this challenge and as a consequence cannot teach us about either realm.
Why positive hole carriers and negatively charged planes are conducive to high temperature superconductivity
APS March meeting, Dallas, Texas, March 2011
(Link to abstract here)
(Link to talk here (pdf, 8.6MB))
Abstract:
The vast majority of superconducting materials have positive Hall coefficient in the normal state, indicating that hole carriers dominate the normal state transport. This was noticed even before BCS theory, and has been amply confirmed by materials found since then: the sign of the Hall coefficient is the strongest normal state predictor of superconductivity. In the superconducting state instead, superfluid carriers are always electron-like, i.e. negative, as indicated by the fact that the magnetic field generated by rotating superconductors is always parallel, never antiparallel, to the body's angular momentum (``London moment''). BCS theory ignores these facts. In contrast, the theory of hole superconductivity, developed over the past 20 years (papers listed in http://physics.ucsd.edu/$\sim $jorge/hole.html) makes charge asymmetry the centerpiece of the action. The Coulomb repulsion between holes is shown to be smaller than that between electrons, thus favoring pairing of holes, and this fundamental electron-hole asymmetry is largest in materials where the conducting structures have \textit{excess negative charge}, as is the case in the cuprates, arsenides and MgB2. Charge asymmetry implies that superconductivity is driven by lowering of kinetic energy, associated with expansion of the carrier wavefunction and with \textit{expulsion of negative charge} from the interior to the surface of the material, where it carries the Meissner current. This results in a macroscopic electric field (pointing outward) in the interior of superconductors, and a macroscopic spin current flowing near the surface in the absence of external fields, a kind of macroscopic zero point motion of the superfluid (spin Meissner effect). London's electrodynamic equations are modified in a natural way to describe this physics. It is pointed out that a dynamical explanation of the Meissner effect \textit{requires} radial outflow of charge in the transition to superconductivity, as predicted by this theory and not predicted by BCS. The theory provides clear guidelines regarding where new higher T$_{c}$ superconductors will and will not be found.
Meissner effect and Spin Meissner effect in superconductors
SLAFES XX, Maragogi, AL, March 27-23, 2011
(conference website)
Abstract:
The Meissner effect[1] and the Spin Meissner effect[2] are the spontaneous
generation of charge and spin current respectively near the surface of a metal
making a transition to the superconducting state. The Meissner effect is well
known but, I argue, not explained by the conventional theory, the Spin Meissner
effect has yet to be detected. I propose that both effects take place in all
superconductors. The speed of the carriers of the predicted spin current is
the speed associated with the critical charge current, since superconductivity
is destroyed when the magnetic field is large enough to bring one component
of the spin current to a halt. I show that both effects can be understood
under the assumption that a metal expels negative charge from the interior
to the surface in the transition to superconductivity[3], a phenomenon which
is predicted by the theory of hole superconductivity, proposed to describe
all superconductors[4, 5] and is not predicted by conventional BCS theory.
The cost in electrostatic energy due to charge separation is compensated by
the lowering of quantum kinetic energy of the system, and the spin current
results from Rashba-like coupling to the resulting internal electric fi eld. The
associated electrodynamics[6] is qualitatively different from London electrodynamics,
yet can be described by a small modification of the conventional
London equations. The stability of the superconducting state and its macroscopic
phase coherence hinge on the fact that the orbital angular momentum
of the carriers of the spin current is found to be exactly hbar/2, indicating a
topological origin. The electric field resulting from the expulsion of negative
charge is found to have magnitude equal to Hc1 (in cgs units) near the surface.
The ground state of superconductors is thus proposed to possess rotational
zero-point motion, suggesting that the same is true in other systems. The
simplicity and universality of our theory argue for its validity. I will discuss
how the existence of superconductivity in various classes of materials can
be understood within our theory, existing experimental evidence for it, and
experiments that should be done to prove it or disprove it.
[1] W. Meissner and R. Ochsenfeld, Naturwissenschaften 21, 787 (1933).
[2] J. E. Hirsch, Europhys. Lett. 81, 67003 (2008).
[3] J. E. Hirsch, Phys.Rev. B 68, 184502 (2003).
[4] J. E. Hirsch and F. Marsiglio, Physica C 162-164, 591 (1989).
[5] J. E. Hirsch, J. Phys. Chem. Solids 67, 21 (2006).
[6] J. E. Hirsch, Phys.Rev. B 69, 214515 (2004); Ann. Phys. (Berlin) 17, 380
(2008).
Correcting 100 years of misunderstanding: electric fields in superconductors, hole superconductivity, and the Meissner effect
8th International Conference on Stripes and High Tc Superconductivity STRIPES 11, Rome, July 10th-16th, 2011
Abstract:
From the outset of superconductivity research it was assumed that no electrostatic fields could exist inside superconductors, and this assumption was incorporated into conventional London electrodynamics. Yet the London brothers themselves initially (in 1935) had proposed an electrodynamic theory of superconductors that allowed for static electric fields in their interior, which they unfortunately discarded a year later. I argue that the Meissner effect in superconductors necessitates the existence of an electrostatic field in their interior, originating in the expulsion of negative charge from the interior to the surface when a metal becomes superconducting. The theory of hole superconductivity predicts this physics, and associated with it a macroscopic spin current in the ground state of superconductors ("Spin Meissner effect"), qualitatively different from what is predicted by conventional BCS-London theory. A new London-like electrodynamic description of superconductors is proposed to describe this physics. Within this theory superconductivity is driven by lowering of quantum kinetic energy, the fact that the Coulomb repulsion strongly depends on the character of the charge carriers, namely whether electron- or hole-like, and the spin-orbit interaction. The electron-phonon interaction does not play a significant role, yet the existence of an isotope effect in many superconductors is easily understood. In the strong coupling regime the theory appears to favor local charge inhomogeneity. The theory is proposed to apply to all superconducting materials, from the elements to the high Tc cuprates and pnictides, is highly falsifiable, and explains a wide variety of experimental observations.
Kinetic energy driven superconductivity and the origin of the Meissner effect in new and old superconductors
E-MRS 2011 Fall Meeting, Warsaw, Poland, September 19-23
Abstract:
It is generally believed that superconducting materials are divided into two classes: `conventional' and `unconventional'. Conventional superconductors (e.g. the elements and thousands of alloys including MgB2) are described by conventional London-BCS-Eliashberg electron-phonon theory. There is no general agreement as to what mechanism or mechanisms describe `unconventional' superconductors such as the heavy fermions, organics, cuprate and pnictide families. Instead, I will argue that there is a single mechanism of superconductivity for all materials. This mechanism differs from the conventional mechanism in several fundamental aspects: in particular, it says that superconductivity is driven by lowering of kinetic rather than potential energy of the charge carriers, and it requires conduction by holes rather than electrons in the normal state. Furthermore I will argue that this mechanism can explain the Meissner effect, exhibited by all superconductors, and that the conventional mechanism cannot. Superconductivity in several different classes of materials will be discussed in the light of these concepts, as well as materials criteria necessary to achieve high temperature superconductivity.
Utilidad y aplicaciones del indice h
para evaluar investigadores
e instituciones
IX FORO INTERNACIONAL SOBRE LA EVALUACION DE LA
CALIDAD DE LA INVESTIGACION Y DE LA EDUCACION SUPERIOR,
Santiago de Compostela, 12-15 de junio, 2012
Explicacion del efecto Meissner y otros efectos en superconductores seguºn la teoria de superconductividad por huecos
Instituto Universitario de Ciencia de Materiales
Nicolas Cabrera, Madrid, Viernes, 15 de junio 2012
Abstract:
La teoria de superconductividad por huecos predice que superconductividad solo ocurre cuando el solido tiene bandas de conduccion casi llenas, y que esta impulsada por una reduccion de la energia cinetica de los portadores. La reduccion de energia cinetica se ha observado experimentalmente en los cupratos. Proponemos que esto explica en forma natural el efecto Meissner que se observa en todos los superconductores, y que otras teorias de superconductividad incluyendo BCS no explican el efecto Meissner. Discutimos varios otros efectos en superconductores, algunos observados y otros todavia no, que se explican por la teoria de superconductividad por huecos y no por otras teorias.
Kinetic energy driven superfluidity and superconductivity and the origin of the Meissner effect
New3SC9, Frascati, Rome, Italy, September 16-20, 2012
Abstract:
Superfluidity and superconductivity have many elements in common. However, I argue that their most important commonality has been overlooked: that both are kinetic energy driven. Clear evidence that superfluidity in 4He is kinetic energy driven is the shape of the lambda transition and the negative thermal expansion coefficient below Tλ. Clear evidence that superconductivity is kinetic energy driven is the Meissner effect: I argue that otherwise the Meissner effect would not take place. Associated with this physics we predict that superconductors expel negative charge from the interior to the surface and that a macroscopic spin current exists in the ground state of superconductors (spin Meissner effect). We propose that this common physics of superconductors and superfluids originates in rotational zero point motion. This view of superconductivity and superfluidity implies that rotational zero-point motion is a fundamental property of the quantum world that is missed in the current understanding.
A unified description of high temperature superconductors,
low temperature superconductors, and superfluid 4He
UC Irvine Condensed Matter Seminar, November 28th, 2012
Abstract:
Progress in science often occurs when seemingly disparate phenomena are found to be describable within a unified framework. However, in the field of superconductivity just the opposite has occurred in the last 40 years: to explain newly discovered superconductors such as heavy fermion compounds, organics, borocarbides, high Tc cuprates, pnictides, non-magnetic oxides, sthrontium ruthenate, etc., many different scenarios have been proposed, distinct from each other and from the universally accepted BCS-electron-phonon theory to describe "conventional" superconductors such as the elements. Instead, I will present a unified description of superconductivity that applies to all superconducting materials. It explains many observations including well known phenomena in "conventional" superconductors that are thought to be understood but I argue are not at all understood in the conventional framework such as the Meissner effect, and predicts new phenomena such as a spin Meissner effect. It also provides guidelines in the search for new high temperature superconductors. Within this description, superconductivity in all materials and superfluidity in 4He are driven by the same physics, lowering of quantum kinetic energy.
High temperature superconductivity:
a scientific crisis awaiting a paradigm shift
Penn State Physics Special Seminar, December 10th, 2013
Abstract:
High temperature cuprate superconductors were discovered 27 years ago, and there is no consensus to date on the origin of the phenomenon. Many other families of superconducting materials have been discovered in the last 40 years that do not fit the conventional framework. A consequence of this is that there are no useful theoretical guidelines in the search for new higher Tc superconducting materials, despite claims to the opposite. I argue that the field is in crisis, and that the reason for this crisis is the unwillingness of the scientific community to consider the possibility that low temperature "conventional" superconductors are not well understood either. I argue that well-known phenomena such as the Meissner effect and the London moment are not explained by the conventional theory of superconductivity. I will describe work by our group started 25 years ago that aims to describe all superconducting materials within the same framework. Within our theory of "hole superconductivity", superconductivity is driven by lowering of quantum kinetic energy of the charge carriers, and can only occur if the carriers in the normal state have hole-like character. The theory provides simple and intuitive explanations for the Meissner effect and the London moment and predicts new phenomena in superconductors as yet unobserved, such as a "Spin Meissner effect". It also provides guidelines in the search for new high temperature superconductors, and reveals an unrecognized deep connection between superconductivity and superfluidity in 4He.
Electron-hole asymmetry and kinetic energy driven superconductivity in dynamic Hubbard models and real materials
Condensed-Matter Physics & Materials Science Seminar, Brookhaven National
Laboratory, February 12th, 2014
Abstract:
Dynamic Hubbard models are simple extensions of the conventional Hubbard model that incorporate the generic fact that electronic orbitals in atoms expand under double electron occupancy, due to electron-electron repulsion. These models are electron-hole asymmetric and lead to superconductivity when electronic energy bands are almost full. Notably, the vast majority of superconducting materials exhibit positive Hall coefficient in the normal state, suggesting that this physics plays a role. Superconductivity described by these models is kinetic-energy-driven, and the superconducting ground state exhibits macroscopic charge inhomogeneity and an electric field in the interior. We predict that this physics takes place in superconducting materials and discuss optical and electron holography experiments that can detect it. These models also explain the Meissner effect and the London moment in a straightforward way.
High temperature superconductivity:
a scientific crisis awaiting a paradigm shift
CCNY Physics Colloquium, March 5th, 2014
Abstract:
High temperature superconductors were discovered 27 years ago (1986), and there is no consensus
to date on the mechanism that drives them, other than it is NOT the BCS electron-phonon
mechanism generally believed to explain low temperature "conventional" superconductors.
Several other families of superconducting materials have been discovered in the last 40 years that
do not fit the BCS framework. I argue that the field is in crisis, and will only make progress once
it is recognized that low temperature "conventional" superconductors are not well understood
either [1]. I will describe work by our group started 25 years ago that aims to describe all
superconducting materials within the same framework [2]: the theory of ``hole superconductivity''
proposes that only hole carriers can give rise to superconductivity, driven by lowering of quantum
kinetic energy. It provides a simple and intuitive explanation for the Meissner effect, predicts new
phenomena in superconductors as yet unobserved such as a "Spin Meissner effect" and the
existence of an electrostatic field in the interior of superconductors, it provides guidelines in the
search for new high temperature superconductors, and reveals an unrecognized deep connection
between superconductivity and superfluidity in 4He.
[1] "BCS theory of superconductivity: it is time to question its validity", Physica Scripta 80, 035702 (2009)
[2] References in: http://physics.ucsd.edu/~jorge/hole.html
Dynamic Hubbard model, high temperature superconductivity and the Meissner effect
Donostia International Physics Center, San Sebastian, Spain, July 4th, 2014
Abstract:
Dynamic Hubbard models describe the physical fact that atomic orbitals expand with increasing electronic occupation, unlike the conventional Hubbard model that ignores this fact. I will show that dynamic Hubbard models lead to high temperature superconductivity driven by lowering of electronic kinetic energy, and to charge inhomogeneity in the normal state, a characteristic feature seen in high temperature superconducting materials. I will also argue that dynamic Hubbard models can explain the Meissner effect and the London moment seen in all superconductors, while models where superconductivity is associated with lowering of the electronic potential energy cannot.
References in:
http://physics.ucsd.edu/~jorge/hole.html
Que es el indice h y su aplicacion a la evaluacion de investigadores e instituciones
XI FORO INTERNACIONAL SOBRE LA EVALUACION DE LA
CALIDAD DE LA INVESTIGACION Y DE LA EDUCACION SUPERIOR,
Bilbao, 8-10 de julio, 2014
Negative charge expulsion, charge inhomogeneity and phase separation in dynamic Hubbard models and in superconducting materials
EMRS Fall Meeting 2014, September 15 - 19, 2014, Warsaw, Poland
Abstract:
Dynamic Hubbard models describe the fact that atomic orbitals are not rigid but expand with increasing electronic occupation. The carriers described by these models when the band is almost full are small electronic polarons dressed by the atomic charge expansion and contraction as they hop from site to site with an increased effective mass and reduced quasiparticle weight. These models predict superconductivity driven by lowering of kinetic energy when a band is almost full (hole carriers), with higher Tc the more negatively charged the ions are. They give rise to negative charge expulsion from the interior to the surface and to charge inhomogeneity and electronic phase separation in the strong coupling regime, to asymmetric tunneling with larger current for a negatively biased sample, to negatively charged grain boundaries, and to multigap behavior with the smaller gap associated with electron-like carriers. We point out that high temperature superconductors such as cuprates, pnictides and magnesium diboride exhibit many of these features. More generally, superconducting materials described by dynamic Hubbard models would often exhibit lattice instabilities, a positive Hall coefficient in the normal state (Chapnik's rule), a small volume per conduction electron (Meissner-Schubert diagram), a magnetic moment parallel to their angular velocity if put into rotation (London moment), and expulsion of magnetic fields due to the expulsion of negative charge (Meissner effect).
References in:
http://physics.ucsd.edu/~jorge/hole.html
A new conception of superconductivity that
is consistent with Faraday's law
Temple University Physics Colloquium, Sept. 29th, 2014
Abstract:
It was pointed out by G. Lippmann in 1919 that a metal cooled into the superconducting
state in the presence of an applied magnetic field would `freeze in' the magnetic field
lines in accordance with Faraday's and Lenz's laws. Experiments by Onnes and Tuyn
(1924) on superconducting spheres were consistent with this basic physical principle.
However, 20 years later Meissner and Ochsenfeld proved Lippmann, Onnes and Tuyn
wrong: superconductors were found to expel magnetic fields. Why were Onnes and Tuyn
wrong? Because to save on the amount of He needed for cooling they had used hollow
rather than solid spheres. Why was Lippmann wrong? This has remained unexplained for
the past 95 years: London's and BCS theories that claim to explain the Meissner effect
are inconsistent with Faraday's law. In this talk I will present a new conception of
superconductivity that is consistent with Faraday's law, explains why Lippmann was
wrong, why cuprates and MgB2 are high temperature superconductors, why most
superconductors have positive Hall coefficient, and how to find new superconductors.
References in:
http://physics.ucsd.edu/~jorge/hole.html