Strongly correlated superconductivity

2018 ◽  
Vol 32 (17) ◽  
pp. 1840023
Author(s):  
T. Yanagisawa ◽  
M. Miyazaki ◽  
K. Yamaji
Keyword(s):  
High Temperature Superconductivity ◽  
Strongly Correlated ◽  
Electron Systems ◽  
Many Body ◽  
Strongly Correlated Electron ◽  
Correlated Electron Systems ◽  
Correlated Electron ◽  
Repulsive Coulomb ◽  
Variational Monte Carlo Method ◽  
The Many

We investigate the electronic properties of the ground state of strongly correlated electron systems. We use an optimization variational Monte Carlo method for the two-dimensional Hubbard model and the three-band d-p model. The many-body wavefunction is improved and optimized by introducing variational parameters that control the correlation between electrons. The on-site repulsive Coulomb interaction U induces strong antiferromagnetic (AF) correlation. There is a crossover from weakly to strongly correlated regions as U increases. We show an idea that high-temperature superconductivity occurs as a result of this crossover in the strongly correlated region where U is greater than the bandwidth.

scholarly journals Crossover Induced Electron Pairing and Superconductivity by Kinetic Renormalization in Correlated Electron Systems

2018 ◽  
Vol 3 (3) ◽  
pp. 26 ◽  
Author(s):  
Takashi Yanagisawa ◽  
Mitake Miyazaki ◽  
Kunihiko Yamaji
Keyword(s):  
Wave Function ◽  
High Temperature ◽  
High Temperature Superconductivity ◽  
Electron System ◽  
Strongly Correlated ◽  
Electron Systems ◽  
Strongly Correlated Electron ◽  
Correlated Electron Systems ◽  
Correlated Electron ◽  
The Many

We investigate the ground state of strongly correlated electron systems based on an optimization variational Monte Carlo method to clarify the mechanism of high-temperature superconductivity. The wave function is optimized by introducing variational parameters in an exponential-type wave function beyond the Gutzwiller function. The many-body effect plays an important role as an origin of superconductivity in a correlated electron system. There is a crossover between weakly correlated region and strongly correlated region, where two regions are characterized by the strength of the on-site Coulomb interaction U. We insist that high-temperature superconductivity occurs in the strongly correlated region.

scholarly journals Thermalization and possible signatures of quantum chaos in complex crystalline materials

2019 ◽  
Vol 116 (40) ◽  
pp. 19869-19874 ◽  
Author(s):  
Jiecheng Zhang ◽  
Erik D. Kountz ◽  
Kamran Behnia ◽  
Aharon Kapitulnik
Keyword(s):  
Thermal Transport ◽  
Quantum Chaos ◽  
Good Description ◽  
Fermi Velocity ◽  
Strongly Correlated ◽  
Electron Systems ◽  
Strongly Correlated Electron ◽  
Correlated Electron Systems ◽  
Correlated Electron ◽  
The Many

Analyses of thermal diffusivity data on complex insulators and on strongly correlated electron systems hosted in similar complex crystal structures suggest that quantum chaos is a good description for thermalization processes in these systems, particularly in the high-temperature regime where the many phonon bands and their interactions dominate the thermal transport. Here we observe that for these systems diffusive thermal transport is controlled by a universal Planckian timescale τ∼ℏ/kBT and a unique velocity vE. Specifically, vE≈vph for complex insulators, and vph≲vE≪vF in the presence of strongly correlated itinerant electrons (vph and vF are the phonon and electron velocities, respectively). For the complex correlated electron systems we further show that charge diffusivity, while also reaching the Planckian relaxation bound, is largely dominated by the Fermi velocity of the electrons, hence suggesting that it is only the thermal (energy) diffusivity that describes chaos diffusivity.

scholarly journals Mechanism of High-Temperature Superconductivity in Correlated-Electron Systems

2019 ◽  
Vol 4 (2) ◽  
pp. 57 ◽  
Author(s):  
Takashi Yanagisawa
Keyword(s):  
High Temperature ◽  
High Temperature Superconductivity ◽  
High Temperature Superconductors ◽  
Energy Scale ◽  
Strongly Correlated ◽  
Electron Systems ◽  
Strong Electron ◽  
Correlated Electron Systems ◽  
Correlated Electron ◽  
Variational Monte Carlo Method

It is very important to elucidate the mechanism of superconductivity for achieving room temperature superconductivity. In the first half of this paper, we give a brief review on mechanisms of superconductivity in many-electron systems. We believe that high-temperature superconductivity may occur in a system with interaction of large-energy scale. Empirically, this is true for superconductors that have been found so far. In the second half of this paper, we discuss cuprate high-temperature superconductors. We argue that superconductivity of high temperature cuprates is induced by the strong on-site Coulomb interaction, that is, the origin of high-temperature superconductivity is the strong electron correlation. We show the results on the ground state of electronic models for high temperature cuprates on the basis of the optimization variational Monte Carlo method. A high-temperature superconducting phase will exist in the strongly correlated region.

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