The two-dimensional $t$-$t^{\prime}$ Holstein model

TL;DR

This paper investigates the effects of next-nearest neighbor hopping on the phase diagram of the Holstein model, revealing a first-order metal-insulator transition and providing a low-temperature phase diagram through quantum Monte Carlo simulations.

Contribution

It introduces an efficient quantum Monte Carlo method for the $t$-$t^{\prime}$ Holstein model and maps out its phase diagram considering external pressure effects.

Findings

Identification of a first-order metal-insulator transition.

Behavior of critical temperature as a function of $t^{\prime}$.

Low-temperature phase diagram of the model.

Abstract

The competition and interplay between charge-density wave and superconductivity have become a central subject for quasi-2D compounds. Some of these materials, such as the transition-metal dichalcogenides, exhibit strong electron-phonon coupling, an interaction that may favor both phases, depending on the external parameters, such as hydrostatic pressure. In view of this, here we analyze the single-band $t$-$t^{\prime}$ Holstein model in the square lattice, adding a next-nearest neighbor hopping $t^{\prime}$ in order to play the role of the external pressure. To this end, we perform unbiased quantum Monte Carlo simulations with an efficient inversion sampling technique appropriately devised for this model. Such a methodology drastically reduces the autocorrelation time, and increases the efficiency of the Monte Carlo approach. By investigating the charge-charge correlation functions, we obtain the behavior of the critical temperature as a function of $t^{\prime}$, and from compressibility analysis, we show that a first-order metal-to-insulator phase transition occurs. We also provide a low-temperature phase diagram for the model.