Random antiferromagnetic quantum spin chains

Daniel S. Fisher
Phys. Rev. B 50, 3799 – Published 1 August 1994
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Abstract

The properties of spin-1/2 antiferromagnetic chains with various types of random exchange coupling are studied via an asymptotically exact decimation renormalization-group transformation, which is a generalization of that introduced by Dasgupta and Ma. Random-singlet phases occur in which each spin is paired with one other spin that may be very far away; more exotic phases also occur. The behavior of typical and mean correlation functions is analyzed and found to be very different, with very small sets of spins dominating the latter at long distances as well as the low-temperature thermodynamics. Some of the phase transitions that occur between antiferromagnetically ordered phases and random singlet or other antiferromagnetic phases are also analyzed. For example, if a small uniaxial anisotropy perturbation is added to a random Heisenberg antiferromagnetic chain, a transition occurs from a random-singlet phase to an Ising antiferromagnetic phase, as the anisotropy changes sign from easy plane to easy axis. The staggered magnetization vanishes at the transition with critical exponent β=8/(1+ √7 ). Possible implications for the properties of random quantum magnetic systems in higher dimensions are briefly discussed.

  • Received 17 March 1994

DOI:https://doi.org/10.1103/PhysRevB.50.3799

©1994 American Physical Society

Authors & Affiliations

Daniel S. Fisher

  • Physics Department, Harvard University, Cambridge, Massachusetts 02138

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Issue

Vol. 50, Iss. 6 — 1 August 1994

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