Bose glass and Mott glass of quasiparticles in a doped quantum magnet

作者：Yu Rong; Yin Liang; Sullivan Neil S; Xia J S; Huan Chao; Paduan Filho Armando; Oliveira Nei F Jr; Haas Stephan; Steppke Alexander; Miclea Corneliu F; Weickert Franziska; Movshovich Roman; Mun Eun Deok; Scott Brian L; Zapf Vivien S; Roscilde Tommaso^*

来源：Nature, 2012, 489(7416): 379-384.

DOI：10.1038/nature11406

The low-temperature states of bosonic fluids exhibit fundamental quantum effects at the macroscopic scale: the best-known examples are Bose-Einstein condensation and superfluidity, which have been tested experimentally in a variety of different systems. When bosons interact, disorder can destroy condensation, leading to a %26apos;Bose glass%26apos;. This phase has been very elusive in experiments owing to the absence of any broken symmetry and to the simultaneous absence of a finite energy gap in the spectrum. Here we report the observation of a Bose glass of field-induced magnetic quasiparticles in a doped quantum magnet (bromine-doped dichloro-tetrakis-thiourea-nickel, DTN). The physics of DTN in a magnetic field is equivalent to that of a lattice gas of bosons in the grand canonical ensemble; bromine doping introduces disorder into the hopping and interaction strength of the bosons, leading to their localization into a Bose glass down to zero field, where it becomes an incompressible Mott glass. The transition from the Bose glass (corresponding to a gapless spin liquid) to the Bose-Einstein condensate (corresponding to a magnetically ordered phase) is marked by a universal exponent that governs the scaling of the critical temperature with the applied field, in excellent agreement with theoretical predictions. Our study represents a quantitative experimental account of the universal features of disordered bosons in the grand canonical ensemble.

• 出版日期2012-9-20