Juan Pablo Álvarez Zúñiga, Nicolas Laflorencie
A spin-wave (SW) approach of the zero temperature superfluid - insulator transition for two dimensional hard-core bosons in a random potential mu=+/- W is developed. While at the classical level there is no intervening phase between the Bose-condensed superfluid (SF) and the gapped disordered insulator, the introduction of quantum fluctuations lead to a much richer physics. Upon increasing the disorder strength W, the Bose-condensed fraction disappears first, before the SF. Then a gapless Bose-glass (BG) phase emerges over a finite region, until the insulator appears. Furthermore, in the strongly disordered SF regime, a mobility edge in the SW excitation spectrum is found at a finite frequency Omega_c, decreasing with W, and presumably vanishing in the BG phase.
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http://arxiv.org/abs/1304.7636
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