NMR study of the S=1/2 Heisenberg Ladder Cu2(C5H12N2)2Cl4 : Quantum phase transition and critical dynamics

TL;DR

This study uses NMR to investigate the quantum phase transition and critical dynamics in a spin-1/2 Heisenberg ladder material under varying magnetic fields, revealing a transition from a gapped spin liquid to a gapless Luttinger liquid.

Contribution

It provides detailed experimental insights into the critical behavior and phase transition dynamics of a Heisenberg ladder system using NMR techniques.

Findings

Identification of the critical field H_c1 at 7.5 T.

Observation of a transition from gapped to gapless magnetic states.

Evidence of a regime dominated by the zero-temperature critical point.

Abstract

We present an extensive NMR study of the spin-1/2 antiferromagnetic Heisenberg ladder Cu2(C5H12N2)2Cl4 in a magnetic field range 4.5 - 16.7 T. By measuring the proton NMR relaxation rate 1/T_1 and varying the magnetic field around the critical field H_c1 = Delta / g\mu_B = 7.5 T, we have studied the transition from a gapped spin liquid ground state to a gapless magnetic regime which can be described as a Luttinger liquid. We identify an intermediate regime T > |H-H_c1|, where the spin dynamics is (possibly) only controlled by the T=0 critical point H_c1.