We study the ground-state phase diagram of the Ashkin-Teller random quantum spin chain by means of a generalization of the strong-disorder renormalization group. In addition to the conventional paramagnetic and ferromagnetic (Baxter) phases, we find a partially ordered phase characterized by strong randomness and infinite coupling between the colors. This unusual phase acts, at the same time, as a Griffiths phase for two distinct quantum phase transitions, both of which are of infinite-randomness type. We also investigate the quantum multicritical point that separates the two-phase and three-phase regions, and we discuss generalizations of our results to higher dimensions and other systems.
F. Hrahsheh et al., "Strong-Randomness Infinite-Coupling Phase in a Random Quantum Spin Chain," Physical review B: Condensed matter and materials physics, vol. 89, no. 1, American Physical Society (APS), Jan 2014.
The definitive version is available at https://doi.org/10.1103/PhysRevB.89.014401
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