Nearly critical ground state of LaCuO2.5

TL;DR

This study investigates the quantum phase transition in LaCuO2.5 using analytical and Quantum Monte Carlo methods, revealing a critical point with universal susceptibility behavior and explaining experimental pseudogap phenomena.

Contribution

It identifies the critical interladder coupling ratio and characterizes the quantum phase transition and crossover behaviors in LaCuO2.5.

Findings

Quantum phase transition at (J'/J)_c ≈ 0.11

Universal T^2 behavior of susceptibility at criticality

Crossover to pseudo-gap behavior at intermediate temperatures

Abstract

Using a combination of analytical techniques and Quantum Monte Carlo simulations we investigate the coupled spin ladder system LaCuO2.5. At a critical ratio of the interladder to intraladder coupling (J'/J)_c \approx 0.11 we find a quantum phase transition between a Neel ordered and a disordered state. At criticality the uniform susceptibility behaves as \chi(T)=aT^2 with a universal prefactor. At intermediate temperatures the system crosses over to a ``decoupled ladders regime'' with pseudo-gap type behavior, similar to uncoupled ladders. This can explain the gap-like experimental data for the magnetic susceptibility of LaCuO2.5 despite the presence of the long range Neel order.