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Communications in Theoretical Physics

Finite-Temperature Optical Conductivity of the Two-Dimensional Hubbard Model

Wenzhu Li, Feng Chen, Tiefeng Xu, He-Ping Ying

Published Oct 30, 1994• 1 citation
Publisher

Abstract

The finite-temperature optical conductivity of the two-dimensional Hubbard model is studied by means of the grand canonical quantum Monte Carlo method. Results are reported for the half-filled and nonhalf-filled band. The formation and variation of Hubbard gap are observed. For the half-filled band case, our results support that there exists a high-temperature insulator-metal transition.

DOI
10.1088/0253-6102/22/3/273

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The finite-temperature optical conductivity of the two-dimensional Hubbard model is studied by means of the grand canonical quantum Monte Carlo method. Results are reported for the half-filled and nonhalf-filled band. The formation and variation of Hubbard gap are observed. For the half-filled band case, our results support that there exists a high-temperature insulator-metal transition.
In the present paper,we attempt to attack the problem of the existence of insu- 1ator- metal transition at finite temperature for a 2 dimensional half- filled Hubbard half- filled model.we used the grand Canonical quantum Monte Carlo method to ca- culate the electrical conductivity and the specific heat of the system. A peak on the specific heat vs temperature curve in high temperature region is observed,and the electrical conductivity curves show a sudden rise in the same temperature region. Thus.our results support that there exists a transition.
摘要 二维半充满条件下的Ｈｕｂｂａｒｄ模型，在有限温度下，是否经历一绝缘体—金属相变？在现有的文献中，这一直是一个有争议而又重要的问题。本文采用巨正则量子Ｍｏｎｔｅ Ｃａｒｌｏ方法，计算了二维半充满条件下Ｈｕｂｂａｒｄ模型的比热和电导率。对不同的库仑排斥势Ｕ（２ｔ－８ｔ），比热曲线在高温区出现一个峰，同时电导率在相应温区呈现一突然上升。因此，计算结果支持存在这样一个相变。 Abstract In the present paper, we attempt to attack the problem of the existence of insulator-metal transition at finite temperature for a 2 dimensional half-filled Hubbard half-filled model. we used the grand Canonical quantum Monte Carlo method to caculate the electrical conductivity and the specific heac of the system. A peak on the specific heat vs temperature curve in high temperature region is observed, and the electrical conductivity curves show a sudden rise in the same temperature region. Thus, our results support that there exists a transition. 作者及机构信息 陈锋, 应和平, 徐铁锋, 李文铸 1. 浙江大学物理系 基金项目: 国家自然科学基金及浙江省自然科学基金资助的课题. Authors and contacts CHHN FENG, YING HE-PING, XU TIE-FENG, LI WEN-ZHU 1. 浙江大学物理系 参考文献 施引文献
The optical conductivity, \ensuremath{\sigma}(\ensuremath{\omega}), of the two-dimensional one-band Hubbard model is calculated at finite temperature using exact diagonalization techniques on finite clusters. The in-plane dc resistivity, ${\mathrm{\ensuremath{\rho}}}_{\mathit{a}\mathit{b}}$, is also evalauted. We find that at large U/t and temperature T, ${\mathrm{\ensuremath{\rho}}}_{\mathit{a}\mathit{b}}$ is approximately linear with temperature. We also observed that \ensuremath{\sigma}(\ensuremath{\omega}) displays charge excitations, a midinfrared (MIR) band, and a Drude peak. The combination of the Drude peak and the MIR oscillator strengths leads to a conductivity that decays slower than 1/${\mathrm{\ensuremath{\omega}}}^{2}$ at energies smaller than the insulator gap near half filling.
We study, by using the quantum Monte Carlo simulation of path-integral form, how the gap is developed in the density of state (DOS) and optical conductivity of the three-dimensional half-filled Hubbard model as a function of the temperature. It is shown that the DOS has a coherent peak just on the Fermi level in the high-temperature region. However, it moves to the high-binding-energy side when the temperature is lowered. The DOS just on the Fermi level is decreased as the decrease of the temperature, and eventually, a gap opens in the DOS. The Drude component in the optical conductivity also decreases with temperature, but it can remain relatively large compared to the DOS at the Fermi level, if the DOS is finite there. We show that the experimentally observed photoemission and optical conductivity spectra of CaVO3{\mathrm{CaVO}}_{3}CaVO3​ are explained within the present theoretical framework effectively and consistently.