TY - JOUR

T1 - Magnon and soliton excitations in the carrier-poor, one-dimensional S = 1/2 antiferromagnet Yb4As3

AU - Steglich, F.

AU - Köppen, M.

AU - Gegenwart, P.

AU - Cichorek, T.

AU - Wand, B.

AU - Lang, M.

AU - Thalmeier, P.

AU - Schmidt, B.

AU - Aoki, H.

AU - Ochiai, A.

PY - 2000/1

Y1 - 2000/1

N2 - The semimetallic quasi-one-dimensional S = 1/2 Heisenberg antiferromagnet Yb4As3 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/(K2 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 ∼ Bν, 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.

AB - The semimetallic quasi-one-dimensional S = 1/2 Heisenberg antiferromagnet Yb4As3 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/(K2 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 ∼ Bν, 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.

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U2 - 10.12693/APhysPolA.97.91

DO - 10.12693/APhysPolA.97.91

M3 - Conference article

AN - SCOPUS:0001899917

VL - 97

SP - 91

EP - 100

JO - Acta Physica Polonica A

JF - Acta Physica Polonica A

SN - 0587-4246

IS - 1

T2 - The European Conference: Physics of Magnetism '99

Y2 - 21 June 1999 through 25 June 1999

ER -