Zero Temperature Phase Transition in Spin-ladders: Phase Diagram and Dynamical studies of Cu(Hp)Cl

TL;DR

This paper investigates the zero-temperature phase transitions in spin-ladders under magnetic fields, analyzing static and dynamical properties near critical points, and mapping them to the XXZ model to understand quantum critical behavior.

Contribution

It provides a detailed experimental and theoretical analysis of quantum critical points in spin-ladders, including universal scaling functions and a mapping to the XXZ model.

Findings

Identification of universal scaling functions near critical points

Mapping of spin-ladders to the XXZ model for detailed analysis

Observation of Luttinger liquid behavior in the gapless phase

Abstract

In a magnetic field, spin-ladders undergo two zero-temperature phase transitions at the critical fields Hc1 and Hc2. An experimental review of static and dynamical properties of spin-ladders close to these critical points is presented. The scaling functions, universal to all quantum critical points in one-dimension, are extracted from (a) the thermodynamic quantities (magnetization) and (b) the dynamical functions (NMR relaxation). A simple mapping of strongly coupled spin ladders in a magnetic field on the exactly solvable XXZ model enables to make detailed fits and gives an overall understanding of a broad class of quantum magnets in their gapless phase (between Hc1 and Hc2). In this phase, the low temperature divergence of the NMR relaxation demonstrates its Luttinger liquid nature as well as the novel quantum critical regime at higher temperature. The general behaviour close these quantum critical points can be tied to known models of quantum magnetism.