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The Low-Energy Fixed Points of Random Quantum Spin Chains

E. Westerberg·A. Furusaki·M. Sigrist·P. A. Lee
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Abstract

The one-dimensional isotropic quantum Heisenberg spin systems with random couplings and random spin sizes are investigated using a real-space renormalization group scheme. It is demonstrated that these systems belong to a universality class of disordered spin systems, characterized by weakly coupled large effective spins. In this large-spin phase the uniform magnetic susceptibility diverges as 1/T with a non-universal Curie constant at low temperatures T, while the specific heat vanishes as T^delta |ln T| for T->0. For broad range of initial distributions of couplings and spin sizes the distribution functions approach a single fixed-point form, where delta \approx 0.44. For some singular initial distributions, however, fixed-point distributions have non-universal values of delta, suggesting that there is a line of fixed points.

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E. Westerberg, A. Furusaki, M. Sigrist, P. A. Lee. 1996-10-22. The Low-Energy Fixed Points of Random Quantum Spin Chains. https://doi.org/10.1103/physrevb.55.12578

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