Suppression of the Mott insulating phase in the particle-hole asymmetric Hubbard model

TL;DR

This study investigates how particle-hole asymmetry affects the Mott metal-insulator transition in the Hubbard model, revealing suppression of the insulating phase and changes in transition characteristics using DMFT.

Contribution

It demonstrates the impact of particle-hole asymmetry on the phase diagram and proposes charge density as an alternative characterization method for the MIT.

Findings

Particle-hole asymmetry decreases the critical temperature $T_c$.

Asymmetry increases the critical interaction $U_c$, suppressing the insulating phase.

Charge density can effectively characterize the MIT.

Abstract

We explore the phase diagram of the Mott metal-insulator transition (MIT), focusing on the effects of particle-hole asymmetry (PHA) in the single-band Hubbard model. Our dynamical mean-field theory (DMFT) study reveals that the introduction of PHA in the model significantly influences the critical temperature ($T_c$) and interaction strength ($U_c$), as well as the size of the co-existence region of metallic and insulating phases at low temperatures. Specifically, as the system is moved away from particle-hole symmetry, $T_c$ decreases and $U_c$ increases, indicating a suppression of the insulating phase and the strengthening of the metallic behavior. Additionally, the first-order transition line between metallic and insulating phases is better defined in the model with PHA, leading to a reduced co-existence region at $T<T_c$. Moreover, we propose that the MIT can be characterized by the charge density, which serves as a viable alternative to zero-frequency spectral density typically used in DMFT calculations. Our findings provide new insights into the role of particle-hole asymmetry in the qualitative and quantitative characterization of the MIT even in a very simple system.