Violation of Luttinger's Theorem in the Two-Dimensional t-J Model

TL;DR

This study calculates high-temperature series for the 2D t-J model's momentum distribution to investigate its Fermi surface, revealing violations of Luttinger's Theorem and suggesting it cannot be connected adiabatically to a non-interacting system.

Contribution

The paper provides the first high-temperature series analysis of the 2D t-J model's momentum distribution, challenging the applicability of Luttinger's Theorem.

Findings

Luttinger's Theorem is violated in the 2D t-J model.

The model's Fermi surface criteria do not match non-interacting predictions.

The 2D t-J model lacks an adiabatic connection to non-interacting systems.

Abstract

We have calculated the high temperature series for the momentum distribution function n_k of the 2D t-J model to 12th order in inverse temperature. By extrapolating the series to T=0.2J we searched for a Fermi surface of the 2D t-J model. We find that three criteria used for estimating the location of a Fermi surface violate Luttinger's Theorem, implying the 2D t-J model does not have an adiabatic connection to a non-interacting model.