Bose-Einstein condensation in antiferromagnets close to the saturation field

Abstract

At zero temperature and strong applied magnetic fields the ground sate of an anisotropic antiferromagnet is a saturated paramagnet with fully aligned spins. We study the quantum phase transition as the field is reduced below an upper critical $H_{c2}$ and the system enters a XY-antiferromagnetic phase. Using a bond operator representation we consider a model spin-1 Heisenberg antiferromagnetic with single-ion anisotropy in hyper-cubic lattices under strong magnetic fields. We show that the transition at $H_{c2}$ can be interpreted as a Bose-Einstein condensation (BEC) of magnons. The theoretical results are used to analyze our magnetization versus field data in the organic compound $NiC{l}_2$-$4SC(N{H}_2{)}_2$ (DTN) at very low temperatures. This is the ideal BEC system to study this transition since $H_{c2}$ is sufficiently low to be reached with static magnetic fields (as opposed to pulsed fields). The scaling of the magnetization as a function of field and temperature close to $H_{c2}$ shows excellent agreement with the theoretical predictions. It allows to obtain the quantum critical exponents and confirm the BEC nature of the transition at $H_{c2}$.

4 pages, 1 figure. Accepted for publication in PRB,

References in corpus (11)

• Realization of Bose-Einstein condensation of dilute magnons in TlCuCl${}_3$
• Coupled Ladders in a Magnetic Field
• Magnetic Field-Induced Condensation of Triplons in Han Purple Pigment BaCuSi${}_2$O${}_6$
• Dimensional reduction at a quantum critical point
• Field- and pressure-induced magnetic quantum phase transitions in TlCuCl_3
• Bose-Einstein Condensation of S = 1 Ni spin degrees of freedom in NiCl2-4SC(NH2)2
• Bose-Einstein Condensation of Magnons in Cs2CuCl4
• Field-Induced Magnetic Order in Quantum Spin Liquids
• Universal scaling at field-induced magnetic phase transitions
• Thermodynamic quantum critical behavior of the Kondo necklace model
• Bose-Einstein condensation and entanglement in magnetic systems

Cited by in corpus (3)

• Interplay of quantum and classical fluctuations near quantum critical points
• Antiferromagnet with two coupled antiferromagnetic sublattices in a magnetic field
• Bose-Einstein Condensation of Magnons in NiCl2-4SC(NH2)2