Field-Controlled Magnetic Order in the Quantum Spin-Ladder System (Hpip)2CuBr4

TL;DR

This study uses neutron diffraction to explore the unconventional field-induced magnetic order in the quantum spin-ladder system (Hpip)2CuBr4, revealing how weak interladder coupling influences the ordered state and its critical properties.

Contribution

It introduces a microscopic model for interladder coupling and calculates quantum fluctuation corrections, advancing understanding of magnetic order in spin-ladder materials.

Findings

Determined the order parameter, transition temperature, and spin structure.

Identified the influence of spin Luttinger-liquid state on magnetic order.

Calculated quantum fluctuation corrections to mean-field interactions.

Abstract

Neutron diffraction is used to investigate the field-induced, antiferromagnetically ordered state in the two-leg spin-ladder material (Hpip)2CuBr4. This "classical" phase, a consequence of weak interladder coupling, is nevertheless highly unconventional: its properties are influenced strongly by the spin Luttinger-liquid state of the ladder subunits. We determine directly the order parameter (transverse magnetization), the ordering temperature, the spin structure, and the critical exponents around the transition. We introduce a minimal, microscopic model for the interladder coupling and calculate the quantum fluctuation corrections to the mean-field interaction.