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arXiv · 1404.2509

Strong-randomness phenomena in quantum Ashkin-Teller models

Hatem Barghathi·Fawaz Hrahsheh·José A. Hoyos·Rajesh Narayanan·Thomas Vojta
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Abstract

The $N$-color quantum Ashkin-Teller spin chain is a prototypical model for the study of strong-randomness phenomena at first-order and continuous quantum phase transitions. In this paper, we first review the existing strong-disorder renormalization group approaches to the random quantum Ashkin-Teller chain in the weak-coupling as well as the strong-coupling regimes. We then introduce a novel general variable transformation that unifies the treatment of the strong-coupling regime. This allows us to determine the phase diagram for all color numbers $N$, and the critical behavior for all $N \ne 4$. In the case of two colors, $N=2$, a partially ordered product phase separates the paramagnetic and ferromagnetic phases in the strong-coupling regime. This phase is absent for all $N>2$, i.e., there is a direct phase boundary between the paramagnetic and ferromagnetic phases. In agreement with the quantum version of the Aizenman-Wehr theorem, all phase transitions are continuous, even if their clean counterparts are of first order. We also discuss the various critical and multicritical points. They are all of infinite-randomness type, but depending on the coupling strength, they belong to different universality classes.

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Hatem Barghathi, Fawaz Hrahsheh, José A. Hoyos, Rajesh Narayanan, Thomas Vojta. 2015-10-08. Strong-randomness phenomena in quantum Ashkin-Teller models. https://doi.org/10.1088/0031-8949%2F2015%2Ft165%2F014040

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