scholarly journals Emergent gauge fields and the high-temperature superconductors

2016 ◽  
Vol 374 (2075) ◽  
pp. 20150248 ◽  
Author(s):  
Subir Sachdev
Keyword(s):  
Fermi Surface ◽  
Free Electron ◽  
Fermi Liquid ◽  
Degrees Of Freedom ◽  
Electron State ◽  
Cuprate Superconductors ◽  
High Temperature Superconductors ◽  
Gauge Fields ◽  
Total Density ◽  
Density Of Electrons

The quantum entanglement of many states of matter can be represented by electric and magnetic fields, much like those found in Maxwell’s theory. These fields ‘emerge’ from the quantum structure of the many-electron state, rather than being fundamental degrees of freedom of the vacuum. I review basic aspects of the theory of emergent gauge fields in insulators in an intuitive manner. In metals, Fermi liquid (FL) theory relies on adiabatic continuity from the free electron state, and its central consequence is the existence of long-lived electron-like quasi-particles around a Fermi surface enclosing a volume determined by the total density of electrons, via the Luttinger theorem. However, long-range entanglement and emergent gauge fields can also be present in metals. I focus on the ‘fractionalized Fermi liquid’ (FL*) state, which also has long-lived electron-like quasi-particles around a Fermi surface; however, the Luttinger theorem on the Fermi volume is violated, and this requires the presence of emergent gauge fields, and the associated loss of adiabatic continuity with the free electron state. Finally, I present a brief survey of some recent experiments in the hole-doped cuprate superconductors, and interpret the properties of the pseudogap regime in the framework of the FL* theory. This article is part of the themed issue ‘Unifying physics and technology in light of Maxwell's equations’.

scholarly journals SPECTRAL ANOMALY AND HIGH TEMPERATURE SUPERCONDUCTORS

1996 ◽  
Vol 10 (07) ◽  
pp. 805-845 ◽  
Author(s):  
LAN YIN ◽  
SUDIP CHAKRAVARTY
Keyword(s):  
High Temperature ◽  
Spectral Function ◽  
Superconducting State ◽  
Fermi Liquid ◽  
Cuprate Superconductors ◽  
High Temperature Superconductors ◽  
Universality Class ◽  
Scaling Relation ◽  
Critical System ◽  
Spectral Anomaly

Spectral anomaly for interacting fermions is characterized by the spectral function A ([k − k F ], ω) satisfying the scaling relation A (Λy1 [k − k F ], Λy2 ω) =ΛyA A ([k − k F ], ω), where y1, y2, and yA are the exponents defining the universality class. For a Fermi liquid y1 = 1, y2 = 1, yA = −1; all other values of the exponents are termed anomalous. In this paper, an example for which y1 = 1, y2 = 1, but yA = α − 1 is considered in detail. Attractive interaction added to such a critical system leads to a novel superconducting state, which is explored and its relevance to high temperature cuprate superconductors is discussed.

SEPARATED SPIN AND CHARGE DEGREES OF FREEDOM IN HIGH-Tc SUPERCONDUCTORS

2005 ◽  
Vol 19 (01n03) ◽  
pp. 193-197
Author(s):  
L. KRUSIN-ELBAUM ◽  
T. SHIBAUCHI ◽  
G. BLATTER
Keyword(s):  
High Temperature ◽  
Magnetic Fields ◽  
Fermi Surface ◽  
Degrees Of Freedom ◽  
High Temperature Superconductors ◽  
Energy Scale ◽  
High Tc Superconductors ◽  
Critical Fields ◽  
High Tc

Recent Nernst and interlayer transport experiments in Bi 2 Sr 2 CaCu 2 O 8+y (BSCCO) high temperature superconductors report hugely different limiting magnetic fields. We demonstrate that both fields convert to the same pseudogap energy scale T* upon transformation as orbital and Zeeman critical fields, respectively. We suggest a consistent interpretation of this finding based on separation of spin and charge degrees of freedom residing in different regions of a truncated Fermi surface.

scholarly journals Mottness collapse and T -linear resistivity in cuprate superconductors

2011 ◽  
Vol 369 (1941) ◽  
pp. 1574-1598 ◽  
Author(s):  
Philip Phillips
Keyword(s):  
Short Range ◽  
Degrees Of Freedom ◽  
Cuprate Superconductors ◽  
High Temperature Superconductors ◽  
Spectral Weight ◽  
Quantum Criticality ◽  
Low Energy ◽  
Energy Theory ◽  
Weight Transfer ◽  
Subsequent Onset

Central to the normal state of cuprate high-temperature superconductors is the collapse of the pseudo-gap, briefly reviewed here, at a critical point and the subsequent onset of the strange metal characterized by a resistivity that scales linearly with temperature. A possible clue to the resolution of this problem is the inter-relation between two facts: (i) a robust theory of T -linear resistivity resulting from quantum criticality requires an additional length scale outside the standard one-parameter scaling scenario and (ii) breaking the Landau correspondence between the Fermi gas and an interacting system with short-range repulsions requires non-fermionic degrees. We show that a low-energy theory of the Hubbard model that correctly incorporates dynamical spectral weight transfer has the extra degrees of freedom needed to describe this physics. The degrees of freedom that mix into the lower band as a result of dynamical spectral weight transfer are shown to either decouple beyond a critical doping, thereby signalling Mottness collapse, or unbind above a critical temperature, yielding strange metal behaviour characterized by T -linear resistivity.

scholarly journals Deformation of the Fermi surface of a spinless two-dimensional electron gas in presence of an anisotropic Coulomb interaction potential

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Orion Ciftja
Keyword(s):  
Fermi Surface ◽  
Coulomb Interaction ◽  
Interaction Potential ◽  
Fermi Liquid ◽  
Energy State ◽  
Electron Gas ◽  
Two Dimensional ◽  
Dimensional Electron ◽  
Two Dimensional Electron Gas ◽  
Dimensional Electron Gas

AbstractWe consider the stability of the circular Fermi surface of a two-dimensional electron gas system against an elliptical deformation induced by an anisotropic Coulomb interaction potential. We use the jellium approximation for the neutralizing background and treat the electrons as fully spin-polarized (spinless) particles with a constant isotropic (effective) mass. The anisotropic Coulomb interaction potential considered in this work is inspired from studies of two-dimensional electron gas systems in the quantum Hall regime. We use a Hartree–Fock procedure to obtain analytical results for two special Fermi liquid quantum electronic phases. The first one corresponds to a system with circular Fermi surface while the second one corresponds to a liquid anisotropic phase with a specific elliptical deformation of the Fermi surface that gives rise to the lowest possible potential energy of the system. The results obtained suggest that, for the most general situations, neither of these two Fermi liquid phases represent the lowest energy state of the system within the framework of the family of states considered in this work. The lowest energy phase is one with an optimal elliptical deformation whose specific value is determined by a complex interplay of many factors including the density of the system.

scholarly journals Shaping quantum photonic states using free electrons

2021 ◽  
Vol 7 (11) ◽  
pp. eabe4270 ◽  
Author(s):  
A. Ben Hayun ◽  
O. Reinhardt ◽  
J. Nemirovsky ◽  
A. Karnieli ◽  
N. Rivera ◽  
...  
Keyword(s):  
Free Electron ◽  
Degrees Of Freedom ◽  
Free Electrons ◽  
Complete Control ◽  
Fock State ◽  
Judicious Choice ◽  
Electron Microscopes ◽  
Photonic States ◽  
Photonic Cavities ◽  
Electron Interactions

It is a long-standing goal to create light with unique quantum properties such as squeezing and entanglement. We propose the generation of quantum light using free-electron interactions, going beyond their already ubiquitous use in generating classical light. This concept is motivated by developments in electron microscopy, which recently demonstrated quantum free-electron interactions with light in photonic cavities. Such electron microscopes provide platforms for shaping quantum states of light through a judicious choice of the input light and electron states. Specifically, we show how electron energy combs implement photon displacement operations, creating displaced-Fock and displaced-squeezed states. We develop the theory for consecutive electron-cavity interactions with a common cavity and show how to generate any target Fock state. Looking forward, exploiting the degrees of freedom of electrons, light, and their interaction may achieve complete control over the quantum state of the generated light, leading to novel light statistics and correlations.

scholarly journals A Two Dimensional Fermi Liquid. Part 3: The Fermi Surface

2004 ◽  
Vol 247 (1) ◽  
pp. 113-177 ◽  
Author(s):  
Joel Feldman ◽  
Horst Kn�rrer ◽  
Eugene Trubowitz
Keyword(s):  
Fermi Surface ◽  
Fermi Liquid ◽  
Two Dimensional ◽  
Liquid Part

Quantum oscillations and the Fermi surface of high-temperature cuprate superconductors

2011 ◽  
Vol 12 (5-6) ◽  
pp. 446-460 ◽  
Author(s):  
Baptiste Vignolle ◽  
David Vignolles ◽  
David LeBoeuf ◽  
Stéphane Lepault ◽  
Brad Ramshaw ◽  
...  
Keyword(s):  
High Temperature ◽  
Fermi Surface ◽  
Cuprate Superconductors ◽  
Quantum Oscillations
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