Criticality and Mott-glass phase in a disordered 2D quantum spin systems

Abstract

We use quantum Monte Carlo simulations to study a disordered S=1/2 Heisenberg quantum spin model with three different nearest-neighbor interactions, J1<=J2<=J3, on the square lattice. We consider the regime in which J1 represents weak bonds, and J2 and J3 correspond to two kinds of stronger bonds (dimers) which are randomly distributed on columns forming coupled 2-leg ladders. When increasing the average intra-dimer coupling (J2+J3)/2, the system undergoes a Neel to quantum glass transition of the ground state and later a second transition into a quantum paramagnet. The quantum glass phase is of the gapless Mott glass type (i.e., in boson language it is incompressible at temperature T = 0), and we find that the temperature dependence of the uniform magnetic susceptibility follows the stretched exponential form x~exp(-b/T^alpha) with 0 < alpha < 1. At the Neel-glass transition we observe the standard O(3) critical exponents, which implies that the Harris criterion for the relevance of the disorder is violated in this system.

11 pages, 15 figures

References in corpus (8)

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• Strong Disorder RG approach - a short review of recent developments
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• Anomalous quantum glass of bosons in a random potential in two dimensions
• Bose and Mott Glass Phases in Dimerized Quantum Antiferromagnets
• Universal scalings of Néel temperature, staggered magnetization density, and spinwave velocity of three-dimensional disordered and clean quantum antiferromagnets
• Validity of Harris criterion for two-dimensional quantum spin systems with quenched disorder
• Quantum transition between magnetically ordered and Mott glass phases
• Universal quantum criticality at finite temperature for two-dimensional disordered and clean dimerized spin-$\frac{1}{2}$ antiferromagnets
• Mott glass phase in a diluted bilayer Heisenberg quantum antiferromagnet
• Ground state energy density, susceptibility, and Wilson ratio of a two-dimensional disordered quantum spin system