Challenges
Datasets
Workspaces
Papers
Discussions
Leaderboard
Log inSign up
Challenges
Datasets
Workspaces
Papers
Discussions
Leaderboard
Blog
Job Board
Q3AS

© 2026 Aqora Quantum S.A.S.

TermsPrivacyLegal Notice

arXiv:1611.02391 · Journal of the Physical Society of Japan

Crossover from Weakly to Strongly Correlated Regions in the Two-dimensional Hubbard Model — Off-diagonal Wave Function Monte Carlo Studies of Hubbard Model II —

Takashi Yanagisawa

Published Oct 16, 2016• 33 citations
arXivHTMLPDF

Abstract

The ground state of the two-dimensional (2D) Hubbard model is investigated by adopting improved wave functions that take into account intersite electron correlation beyond the Gutzwiller ansatz. The ground-state energy is lowered considerably, giving the best estimate of the ground-state energy for the 2D Hubbard model. There is a crossover from weakly to strongly correlated regions as the on-site Coulomb interaction $U$ increases. The antiferromagnetic correlation induced by $U$ is reduced for hole doping when $U$ is large, being greater than the bandwidth, thus increasing the kinetic energy gain. The spin and charge fluctuations are induced in the strongly correlated region. These antiferromagnetic and kinetic charge fluctuations induce electron pairings, which would result in high-temperature superconductivity.

DOI
10.7566/jpsj.85.114707

Related papers

Strongly correlated superconductivity

Takashi Yanagisawa, Masanori Miyazaki, Yamaji K.

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.

International Journal of Modern Physics B•Mar 29, 2018•1 citation

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

Takashi Yanagisawa

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 repulsion U . We show that the antiferromagnetic correlation is suppressed as U is increased exceeding the bandwidth. High-temperature superconductivity is possible in this region with enhanced antiferromagnetic spin fluctuation and pairing interaction.

Advances in Condensed Matter Physics•Jan 1, 2015•0 citations

Superconductivity and Inhomogeneous Charge-Ordered State in the Two-Dimensional Hubbard Model —Off-Diagonal Wave Function Monte Carlo Studies of Hubbard Model IV—

Takashi Yanagisawa

We investigate the ground-state properties of the two-dimensional Hubbard model, based on the off-diagonal wave function variational Monte Carlo method. We use an optimized wave function that is improved from an initial one-body wave function by multiplying by multiple correlation operators that are given by the form of exp($-S$)-type where $S$ is a suitable operator. We examine the inhomogeneous ground state at near 1/8 doping in the strongly correlated region where the on-site Coulomb interaction is larger than the bandwidth. The $d$-wave superconductivity with a spatially oscillating gap function can coexist with the charge ordering in the ground state without magnetic ordering, and superconducting condensation energy increases by this coexistence. We also show the $d$-wave pair correlation function as a function of lattice sites. The correlation function indicates that the long-range superconducting order indeed exists, and also that the strong electron correlation suppresses the pair correlation function.

arXiv:2506.12736•Journal of the Physical Society of Japan•Jun 20, 2025•0 citations

Magnetsim, Fluctuations and Mechanism of High-Temperature Superconductivity

Takashi Yanagisawa, Izumi Hase, Mitake Miyazaki +1 more

We investigate the ground state of the two-dimensional d-p model (three-band Hubbard model) by using a variational Monte Carlo method. The superconducting condensation energy is evaluated for the Gutzwiller-BCS wave function. We show that there is a crossover between strongly and weakly correlated regions as the level difference between d and p orbitals increases. The gap function and the condensation energy can be large in the crossover region. This result indicates a possibility of high-temperature superconductivity in the two-dimensional d-p model.

Journal of Physics Conference Series•Jul 1, 2017•0 citations

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

Takashi Yanagisawa, Masanori Miyazaki, Yamaji K.

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.

Modern Physics Letters B•Jul 3, 2020•2 citations

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

Takashi Yanagisawa, Mitake Miyazaki, Yamaji K.

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.

Condensed Matter•Sep 6, 2018•1 citation
The ground state of the two-dimensional (2D) Hubbard model is investigated by adopting improved wave functions that take into account intersite electron correlation beyond the Gutzwiller ansatz. The ground-state energy is lowered considerably, giving the best estimate of the ground-state energy for the 2D Hubbard model. There is a crossover from weakly to strongly correlated regions as the on-site Coulomb interaction UUU increases. The antiferromagnetic correlation induced by UUU is reduced for hole doping when UUU is large, being greater than the bandwidth, thus increasing the kinetic energy gain. The spin and charge fluctuations are induced in the strongly correlated region. These antiferromagnetic and kinetic charge fluctuations induce electron pairings, which would result in high-temperature superconductivity.
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.
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 repulsion U . We show that the antiferromagnetic correlation is suppressed as U is increased exceeding the bandwidth. High-temperature superconductivity is possible in this region with enhanced antiferromagnetic spin fluctuation and pairing interaction.
We investigate the ground-state properties of the two-dimensional Hubbard model, based on the off-diagonal wave function variational Monte Carlo method. We use an optimized wave function that is improved from an initial one-body wave function by multiplying by multiple correlation operators that are given by the form of exp(−S-S−S)-type where SSS is a suitable operator. We examine the inhomogeneous ground state at near 1/8 doping in the strongly correlated region where the on-site Coulomb interaction is larger than the bandwidth. The ddd-wave superconductivity with a spatially oscillating gap function can coexist with the charge ordering in the ground state without magnetic ordering, and superconducting condensation energy increases by this coexistence. We also show the ddd-wave pair correlation function as a function of lattice sites. The correlation function indicates that the long-range superconducting order indeed exists, and also that the strong electron correlation suppresses the pair correlation function.
We investigate the ground state of the two-dimensional d-p model (three-band Hubbard model) by using a variational Monte Carlo method. The superconducting condensation energy is evaluated for the Gutzwiller-BCS wave function. We show that there is a crossover between strongly and weakly correlated regions as the level difference between d and p orbitals increases. The gap function and the condensation energy can be large in the crossover region. This result indicates a possibility of high-temperature superconductivity in the two-dimensional d-p 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.
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.