Four-spin-exchange- and magnetic-field-induced chiral order in two-leg spin ladders

Masahiro Sato
Phys. Rev. B 76, 054427 – Published 14 August 2007

Abstract

We propose a mechanism of a vector chiral long-range order in two-leg spin-12 and spin-1 antiferromagnetic ladders with four-spin exchanges and a Zeeman term. It is known that for one-dimensional quantum systems, spontaneous breakdown of continuous symmetries is generally forbidden. Any vector chiral order hence does not appear in spin-rotationally [SU(2)]-symmetric spin ladders. However, if a magnetic field is added along the Sz axis of ladders and the SU(2) symmetry is reduced to the U(1) one, the z component of a vector chiral order can emerge with the remaining U(1) symmetry unbroken. Making use of Abelian bosonization techniques, we actually show that a certain type of four-spin exchange can yield a vector chiral long-range order in spin-12 and spin-1 ladders under a magnetic field. In the chiral-ordered phase, the Z2 interchain-parity (i.e., chain-exchange) symmetry is spontaneously broken. We also consider effects of perturbations breaking the parity symmetry.

  • Figure
  • Received 24 January 2007

DOI:https://doi.org/10.1103/PhysRevB.76.054427

©2007 American Physical Society

Authors & Affiliations

Masahiro Sato

  • Synchrotron Radiation Research Center, Japan Atomic Energy Agency, Sayo, Hyogo 679-5148, Japan; CREST Japan Science and Technology Agency, Kawaguchi, Saitama 332-0012, Japan; and Condensed Matter Theory Laboratory, RIKEN, Wako, Saitama 351-0198, Japan

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Issue

Vol. 76, Iss. 5 — 1 August 2007

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