Two distinct Mott-insulator to Bose-glass transitions and breakdown of self-averaging in the disordered Bose-Hubbard model

Article

关键词: SUPERFLUID TRANSITION;    SYSTEMS;    RENORMALIZATION;    SUPERCONDUCTORS;    FLUCTUATIONS;    LOCALIZATION;    DIMENSIONS;   

DOI  :  10.1103/PhysRevB.84.115118

来源: SCIE

【 摘 要 】

We investigate the instabilities of the Mott-insulating phase of the weakly disordered Bose-Hubbard model within a renormalization group analysis of the replica field theory obtained by a strong-coupling expansion around the atomic limit. We identify an order parameter and associated correlation length scale that are capable of capturing the transition from a state with zero compressibility, the Mott insulator, to one in which the compressibility is finite, the Bose glass. The order parameter is the relative variance of the disorder-induced mass distribution. In the Mott insulator, the relative variance renormalizes to zero, whereas it diverges in the Bose glass. The divergence of the relative variance signals the breakdown of self-averaging. The length scale governing the breakdown of self-averaging is the distance between rare regions. This length scale is finite in the Bose glass but diverges at the transition to the Mott insulator with an exponent of nu = 1/D for incommensurate fillings. Likewise, the compressibility vanishes with an exponent of gamma = 4/D - 1 at the transition. At commensurate fillings, the transition is controlled by a different fixed point at which both the disorder and interaction vertices are relevant.

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