Luttinger-Liquid Behavior in the Alternating Spin-Chain System Copper Nitrate

TL;DR

This paper investigates copper nitrate as an ideal system to explore quantum phase transitions, demonstrating Luttinger liquid behavior, 3D Bose-Einstein condensation, and the crossover between 1D and 3D physics through experimental and theoretical analysis.

Contribution

It establishes copper nitrate as a prime candidate for studying quasi-1D Luttinger liquids and the crossover to 3D order, supported by comprehensive experimental and theoretical work.

Findings

Evidence of Luttinger liquid regime from neutron scattering and magnetization data.

Observation of 3D long-range order induced by magnetic field.

Complete phase diagram of copper nitrate in the context of quantum phase transitions.

Abstract

We determine the phase diagram of copper nitrate Cu(NO$_3$)$_2\cdot$2.5D$_2$O in the context of quantum phase transitions and novel states of matter. We establish this compound as an ideal candidate to study quasi-1D Luttinger liquids, 3D Bose-Einstein-Condensation of triplons, and the crossover between 1D and 3D physics. Magnetocaloric effect, magnetization, and neutron scattering data provide clear evidence for transitions into a Luttinger liquid regime and a 3D long-range ordered phase as function of field and temperature. Theoretical simulations of this model material allow us to fully establish the phase diagram and to discuss it in the context of dimerized spin systems.