Universal relaxational dynamics near two-dimensional quantum critical points

Article

关键词: EXACT MASS GAP;    LOW-TEMPERATURES;    HEISENBERG-ANTIFERROMAGNET;    PHASE FLUCTUATIONS;    2 DIMENSIONS;    XY MODEL;    SUPERCONDUCTIVITY;    TRANSITION;    LACUO2.5;    SYSTEMS;   

DOI  :  10.1103/PhysRevB.59.14054

来源: SCIE

【 摘 要 】

We describe the nonzero temperature (T), low frequency (omega) dynamics of the order parameter near quantum critical points in two spatial dimensions (d), with a special focus on the regime h omega much less than k(B)T. For the case of a relativistic, O(n)-symmetric, bosonic quantum held theory we show that, for small epsilon=3-d, the dynamics is described by an effective classical model of waves with a quartic interaction. We provide analytical and numerical analyses of the classical wave model directly in d=2. We describe the crossover from the finite frequency, amplitude fluctuation, gapped quasiparticle mode in the quantum paramagnet (or Mott insulator), to the zero frequency phase (n greater than or equal to 2) or domain wall (n = 1) relaxation mode near the ordered state. For static properties, we show how a surprising, duality-like transformation allows an exact treatment of the strong-coupling limit for all n. For n = 2, we compute the universal T dependence of the superfluid density below the Kosterlitz-Thouless temperature, and discuss implications for the high temperature superconductors. For n = 3, our computations of the dynamic structure factor relate to neutron scattering experiments on La1.85Sr0.15Cu O-4, and to light scattering experiments on double layer quantum Hall systems. We expect that closely related effective classical wave models will apply also to other quantum critical points in d=2. Although computations in appendixes do rely upon technical results on the epsilon-expansion of quantum critical points obtained in earlier papers, the physical discussion in the body of the paper is self-contained, and can be read without consulting these earlier works. [S0163-1829(99)03821-7].

【 授权许可】

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