Lee-Yang formalism for phase transitions of interacting fermions using tensor networks

TL;DR

This paper introduces a novel formalism combining Lee-Yang theory and tensor networks to accurately map phase diagrams and identify critical points in interacting fermionic systems through order parameter fluctuations.

Contribution

It presents a new method for determining phase boundaries in fermionic systems by analyzing cumulants and zeros of the moment-generating function using tensor networks.

Findings

Successfully mapped phase diagram of a fermionic chain with charge density waves

Identified phase transition boundaries through extrapolation of zeros in finite chains

Provided a measurable approach based on order parameter fluctuations

Abstract

Predicting the phase diagram of interacting quantum many-body systems is a challenging problem in condensed matter physics. Strong interactions and correlation effects may lead to exotic states of matter, such as quantum spin liquids and unconventional superconductors, that often compete with other symmetry broken states including ordered magnets and charge density waves. Here, we put forward a formalism for determining the phase diagram of fermionic systems that combines recent progress in the field of Lee-Yang theory of phase transitions with many-body tensor-network methods. Using this strategy, we map out the phase diagram of a fermionic chain, where charge density waves form owing to strong repulsion. Specifically, from the high cumulants of the order parameter, we extract the dominant zeros of the moment-generating function in chains of finite size. By extrapolating their positions to the thermodynamic limit, we determine the boundaries between competing phases. Our formalism provides a strategy for determining critical points in fermionic systems, and it is based on fluctuations of the order parameter, which are measurable quantities.