Magnetic-Field Induced Bose-Einstein Condensation of Magnons and Critical Behavior in Interacting Spin Dimer System TlCuCl$_3$

TL;DR

This study investigates the critical behavior of magnon Bose-Einstein condensation in the gapped spin system TlCuCl3 through magnetization measurements, confirming theoretical predictions and analyzing phase boundary behavior.

Contribution

The paper provides experimental validation of magnon BEC theory in TlCuCl3, including precise measurements of critical density, interaction constants, and phase boundary behavior.

Findings

Critical density of magnons as a function of temperature.

Phase boundary matches magnon BEC theory predictions.

Critical exponent approaches 3/2 at low temperatures.

Abstract

Magnetization measurements were performed to investigate the critical behavior of the field-induced magnetic ordering in gapped spin system TlCuCl$_3$. The critical density of the magnons was obtained as a function of temperature and the magnon-magnon interaction constant was evaluated. The experimental phase boundary for $T < 5$ K agrees almost perfectly with the magnon BEC theory based on the Hartree-Fock approximation with realistic dispersion relations. The phase boundary can be described by the power law $[H_{N}(T)-H_{c}] propto T^{phi}$. With decreasing fitting temperature range, the critical exponent ${phi}$ decreases and converges at $phi_{BEC} =3/2$ predicted by the magnon BEC theory.