## Abstract

The semimetallic quasi-one-dimensional S = 1/2 Heisenberg antiferromagnet Yb_{4}As_{3} was studied by low-temperature measurements of the specific heat C(T, B), thermal expansion α(T, B), and thermal conductivity κ(T, B). At finite magnetic fields (B ≤ 12 T) we observed the following distinct anomalies: (1) the magnon contribution to C(T, 0), γT, with large coefficient γ ≈ 200 mJ/(K^{2} mol), becomes strongly reduced with field, and (2) a broad hump in C(T, B = const) is induced at slightly higher temperatures. (3) The latter corresponds to a pronounced peak in α(T, B = const) as well as (4) to a broad minimum in κ(T, B = const)/κ(T, 0). These anomalies are well described by the classical sine-Gordon solution of a one-dimensional Heisenberg antiferromagnet with a weak easy-plane anisotropy. However, the soliton-rest energy deduced from the experimental results depends on the magnetic field like Es ∼ B^{ν}, with an exponent ν ≈ 0.66, while the classical sine-Gordon model requires ν = 1. Thus, our results suggest an alternative description of soliton excitations in an antiferromagnetic S = 1/2 Heisenberg chain in terms of the quantum sine-Gordon model, for which an exponent ν = 2/3 is appropriate.

Original language | English |
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Pages (from-to) | 91-100 |

Number of pages | 10 |

Journal | Acta Physica Polonica A |

Volume | 97 |

Issue number | 1 |

DOIs | |

Publication status | Published - 2000 Jan |

Externally published | Yes |

Event | The European Conference: Physics of Magnetism '99 - Poznan, Poland Duration: 1999 Jun 21 → 1999 Jun 25 |

## ASJC Scopus subject areas

- Physics and Astronomy(all)

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