scholarly journals On the Kinetic Energy Driven Superconductivity in the Two-Dimensional Hubbard Model

2021 ◽  
Vol 6 (1) ◽  
pp. 12
Author(s):  
Takashi Yanagisawa ◽  
Kunihiko Yamaji ◽  
Mitake Miyazaki
Keyword(s):  
Wave Function ◽  
Kinetic Energy ◽  
Hubbard Model ◽  
High Temperature Superconductivity ◽  
Repulsive Interaction ◽  
Two Dimensional ◽  
Condensation Energy ◽  
Energy Effect ◽  
Correlation Operator ◽  
Correlated Electron

We investigate the role of kinetic energy for the stability of superconducting state in the two-dimensional Hubbard model on the basis of an optimization variational Monte Carlo method. The wave function is optimized by multiplying by correlation operators of site off-diagonal type. This wave function is written in an exponential-type form given as ψλ=exp(−λK)ψG for the Gutzwiller wave function ψG and a kinetic operator K. The kinetic correlation operator exp(−λK) plays an important role in the emergence of superconductivity in large-U region of the two-dimensional Hubbard model, where U is the on-site Coulomb repulsive interaction. We show that the superconducting condensation energy mainly originates from the kinetic energy in the strongly correlated region. This may indicate a possibility of high-temperature superconductivity due to the kinetic energy effect in correlated electron systems.

Phase diagram of cuprate high-temperature superconductors based on the optimization Monte Carlo method

2020 ◽  
Vol 34 (19n20) ◽  
pp. 2040046
Author(s):  
T. Yanagisawa ◽  
M. Miyazaki ◽  
K. Yamaji
Keyword(s):  
Phase Diagram ◽  
Monte Carlo ◽  
Wave Function ◽  
High Temperature ◽  
Hubbard Model ◽  
Ground State ◽  
State Energy ◽  
High Temperature Superconductivity ◽  
Two Dimensional ◽  
Text Model

It is important to understand the phase diagram of electronic states in the CuO2 plane to clarify the mechanism of high-temperature superconductivity. We investigate the ground state of electronic models with strong correlation by employing the optimization variational Monte Carlo method. We consider the two-dimensional Hubbard model as well as the three-band [Formula: see text]–[Formula: see text] model. We use the improved wave function that takes account of inter-site electron correlation to go beyond the Gutzwiller wave function. The ground state energy is lowered considerably, which now gives the best estimate of the ground state energy for the two-dimensional Hubbard model. The many-body effect plays an important role as an origin of spin correlation and superconductivity in correlated electron systems. We investigate the competition between the antiferromagnetic state and superconducting state by varying the Coulomb repulsion [Formula: see text], the band parameter [Formula: see text] and the electron density [Formula: see text] for the Hubbard model. We show phase diagrams that include superconducting and antiferromagnetic phases. We expect that high-temperature superconductivity occurs near the boundary between antiferromagnetic phase and superconducting one. Since the three-band [Formula: see text]–[Formula: see text] model contains many-band parameters, high-temperature superconductivity may be more likely to occur in the [Formula: see text]–[Formula: see text] model than in single-band models.

scholarly journals Superconductivity in the two-dimensional Hubbard model: Gutzwiller wave function solution

2013 ◽  
Vol 88 (11) ◽  
Author(s):  
Jan Kaczmarczyk ◽  
Jozef Spałek ◽  
Tobias Schickling ◽  
Jörg Bünemann
Keyword(s):  
Wave Function ◽  
Hubbard Model ◽  
Two Dimensional ◽  
Function Solution

scholarly journals Superconductivity, Antiferromagnetism, and Kinetic Correlation in Strongly Correlated Electron Systems

2015 ◽  
Vol 2015 ◽  
pp. 1-5
Author(s):  
Takashi Yanagisawa
Keyword(s):  
High Temperature ◽  
Hubbard Model ◽  
High Temperature Superconductivity ◽  
Spin Fluctuation ◽  
Coulomb Repulsion ◽  
Strongly Correlated Electron ◽  
Correlated Electron Systems ◽  
Correlated Electron ◽  
Antiferromagnetic Correlation ◽  
The Stability

We investigate the ground state of two-dimensional Hubbard model on the basis of the variational Monte Carlo method. We use wave functions that include kinetic correlation and doublon-holon correlation beyond the Gutzwiller ansatz. It is still not clear whether the Hubbard model accounts for high-temperature superconductivity. The antiferromagnetic correlation plays a key role in the study of pairing mechanism because the superconductive phase exists usually close to the antiferromagnetic phase. We investigate the stability of the antiferromagnetic state when holes are doped as a function of the Coulomb repulsionU. We show that the antiferromagnetic correlation is suppressed asUis increased exceeding the bandwidth. High-temperature superconductivity is possible in this region with enhanced antiferromagnetic spin fluctuation and pairing interaction.

REMARK ON THE EXISTENCE OF LONG-RANGE ORDER IN QUASI-TWO-DIMENSIONAL HUBBARD MODEL

1996 ◽  
Vol 10 (08) ◽  
pp. 341-346 ◽  
Author(s):  
A. BELKASRI ◽  
J.L. RICHARD
Keyword(s):  
Thin Film ◽  
High Temperature ◽  
Theoretical Analysis ◽  
Hubbard Model ◽  
Long Range ◽  
High Temperature Superconductivity ◽  
Type Model ◽  
Long Range Order ◽  
Two Dimensional ◽  
2D System

Recently in many works on the mechanism of high temperature superconductivity (see for example Refs. 1–6), quasi-averages like <ck↑c−k↓> were considered even in the case of a dimension less or equal two. But it is well known from the old work of Hohenberg7 that these quasi-averages are zero at T≠0 in case of 1 and 2 dimensions. In this communication we generalize the Hohenberg’s result to any kind of Hubbard type model on lattice and prove that in the case of quasi-two-dimension, the theorem of Hohenberg is not in contradiction with having <ck↑c−k↓>≠0 (at T≠0). In practice this makes sense to compare the data for a thin film (which can be considered as quasi-2D system) to the theoretical analysis based on quasi-two-dimensional models, but not for strictly two-dimensional case.

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