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arXiv · 1701.08624

Quantum transition between magnetically ordered and Mott glass phases

A. V. Syromyatnikov
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Abstract

We discuss a quantum transition from a superfluid to a Mott glass phases in disordered Bose-systems by the example of an isotropic spin-$\frac12$ antiferromagnet with spatial dimension $d\ge2$ and with disorder in tunable exchange couplings. Our analytical consideration is based on general properties of a system in critical regime, on the assumption that the magnetically order part of the system shows fractal properties near the transition, and on a hydrodynamic description of long-wavelength magnons in the magnetically ordered ("superfluide") phase. Our results are fully consistent with a scaling theory based on an ansatz for the free energy proposed by M.P. Fisher et al. (Phys. Rev. B 40, 546 (1989)). We obtain $z=d-β/ν$ for the dynamical critical exponent and $ϕ= zν$, where $ϕ$, $β$, and $ν$ are critical exponents of the critical temperature, the order parameter, and the correlation length, respectively. The density of states of localized excitations (fractons) is found to show a superuniversal (i.e., independent of $d$) behavior.

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A. V. Syromyatnikov. 2017-08-03. Quantum transition between magnetically ordered and Mott glass phases. https://doi.org/10.1002/andp.201700055

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