Bose-Einstein Condensation of Triplons in Ba3Cr2O8

TL;DR

This study maps the phase diagram of Ba3Cr2O8 under high magnetic fields, providing evidence for Bose-Einstein condensation of triplons and revealing a first-order transition at higher fields.

Contribution

It presents experimental evidence for Bose-Einstein condensation of triplons in Ba3Cr2O8 and distinguishes the nature of phase transitions at different magnetic field ranges.

Findings

Field-induced magnetic order between 12.52 T and 23.65 T

Maximum transition temperature of 2.7 K at 18 T

Lower transition consistent with Bose-Einstein condensation of triplons

Abstract

By performing heat capacity, magnetocaloric effect, torque magnetometry and force magnetometry measurements up to 33 T, we have mapped out the T-H phase diagram of the S = 1/2 spin dimer compound Ba3Cr2O8. We found evidence for field-induced magnetic order between Hc1 = 12.52(2) T and Hc2 = 23.65(5) T, with the maximum transition temperature Tc = 2.7 K at H = 18 T. The lower transition can likely be described by Bose-Einstein condensation of triplons theory, and this is consistent with the absence of any magnetization plateaus in our magnetic torque and force measurements. In contrast, the nature of the upper phase transition appears to be quite different as our measurements suggest that this transition is actually first order.