Universal phase diagram of disordered bosons from a doped quantum magnet

¹  Department of Physics and Astronomy, Rice University - Houston, TX 77005, USA
²  Department of Physics and Astronomy, University of Southern California - Los Angeles, CA 90089-0484, USA
³  Laboratoire de Physique, Ecole Normale Supérieure de Lyon - 46 Allée d'Italie, 69007 Lyon, France, EU
⁴  Max-Planck-Institut für Quantenoptik - Hans-Kopfermann-strasse 1, 85748 Garching, Germany, EU

Corresponding author: tommaso.roscilde@ens-lyon.fr

Received: 15 December 2009
Accepted: 18 December 2009

Abstract

A quantum particle cannot in general diffuse through a disordered medium because of its wavelike nature, but interacting particles can escape localization by collectively percolating through the system. For bosonic particles this phenomenon corresponds to a quantum transition from a localized insulator phase —the Bose glass— to a superfluid phase, in which particles condense into an extended state. Here, we construct a universal phase diagram of disordered bosons in doped quantum magnets for which bosonic quasiparticles are represented by magnetized states (spin triplets) of the quantum spins, condensing into a magnetically ordered state. The appearance of a Bose glass leads to strong measurable signatures in the onset of superfluidity of the spin-triplet gas, exhibiting a complex crossover from low-temperature quantum percolation to a conventional condensation transition at intermediate temperatures.