Thermodynamic properties of the planar $t-J$ model

TL;DR

This study uses the $T>0$ Lanczos method to analyze thermodynamic properties of the planar $t-J$ model, revealing non-Fermi liquid behavior, Fermi surface transition, and doping-dependent magnetic features relevant to cuprates.

Contribution

It provides detailed thermodynamic calculations of the $t-J$ model at finite temperature, highlighting doping-dependent phenomena and phase transitions not previously characterized.

Findings

Hole density shows non-Fermi liquid behavior with temperature.

Specific heat peaks at the exchange energy scale for certain doping levels.

Spin susceptibility exhibits a maximum at finite temperature, decreasing with doping.

Abstract

Several thermodynamic quantities within the planar $t-J$ model are calculated using the $T>0$ Lanczos method on clusters of up to 26 sites. Hole density $c_h(\mu,T)$ shows a non-Fermi liquid behavior as a function of $T$ and suggests a transition from small to large Fermi surface at $c_h\sim 0.15$. Specific heat reveals a maximum at the exchange energy-scale up to $c_h=0.2$, where it becomes almost $T$-independent for $T\agt 0.15~t$. At constant $T$ the entropy has maximum for $c_h\sim 0.15$, with large values at low $T$, consistent with experiments on cuprates. In the underdoped regime the spin susceptibility $\chi_0(T)$ exhibits a maximum at finite $T = T^*$, with $T^*$ decreasing with doping, and disappearing for $c_h>0.15$.