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Extreme sensitivity of a frustrated quantum magnet: Cs2CuCl4

Oleg A. Starykh, Hosho Katsura, and Leon Balents
Phys. Rev. B 82, 014421 – Published 20 July 2010
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Abstract

We report a thorough theoretical study of the low temperature phase diagram of Cs2CuCl4, a spatially anisotropic spin S=12 triangular lattice antiferromagnet, in a magnetic field. Our results, obtained in a quasi-one-dimensional limit in which the system is regarded as a set of weakly coupled Heisenberg chains, are in excellent agreement with experiment. The analysis reveals some surprising physics. First, we find that when the magnetic field is oriented within the triangular layer, spins are actually most strongly correlated within planes perpendicular to the triangular layers. This is despite the fact that the interlayer exchange coupling in Cs2CuCl4 is about an order of magnitude smaller than the weakest (diagonal) exchange in the triangular planes themselves. Second, the phase diagram in such orientations is exquisitely sensitive to tiny interactions, heretofore neglected, of order a few percent or less of the largest exchange couplings. These interactions, which we describe in detail, induce entirely new phases, and a novel commensurate-incommensurate transition, the signatures of which are identified in NMR experiments. We discuss the differences between the behavior of Cs2CuCl4 and an ideal two-dimensional triangular model, and in particular, the occurrence of magnetization plateaux in the latter. These and other related results are presented here along with a thorough exposition of the theoretical methods, and a discussion of broader experimental consequences to Cs2CuCl4 and other materials.

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  • Received 7 May 2010

DOI:https://doi.org/10.1103/PhysRevB.82.014421

©2010 American Physical Society

Synopsis

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Extreme sensitivity

Published 20 July 2010

Even tiny interactions can dominate the properties of a frustrated quantum magnet at low temperatures.

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Authors & Affiliations

Oleg A. Starykh1, Hosho Katsura2, and Leon Balents2

  • 1Department of Physics and Astronomy, University of Utah, Salt Lake City, Utah 84112, USA
  • 2Kavli Institute for Theoretical Physics, University of California, Santa Barbara, California 93106-9530, USA

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Issue

Vol. 82, Iss. 1 — 1 July 2010

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