Magnetic-field dependence of the specific heat in planar spin chains

Noboru Fukushima, A. Honecker, Stefan Weßel +2 more

Gennady Sh. Gildenblat

We use a pseudofermion representation to investigate strong-field anomalies of the magnetic-field (h) dependence of the specific heat (c) of a spin-1/2 XY chain doped with magnetic impurities. If at certain magnetic field the impurity-induced split-off energy levels come sufficiently close to the chemical potential of pseudofermions (zero), then at low temperatures the specific heat of the chain is significantly altered by even a small number of impurities. The impurity-induced peaks of the c(h) dependence correspond to magnetic fields in a range where the specific heat of the ideal spin-1/2 XY chains is exponentially small. They have the same physical origin, but different structure, as compared to the high-field anomalies of longitudinal magnetic susceptibility investigated previously.

Jinshan Wu, Mona Berciu

N. Papanicolaou, P Spathis

The magnetic specific heat in a class of spin- 1 / 2 chains with uniaxial anisotropy is determined accurately by a numerical solution of certain integral equations derived earlier through the Bethe ansatz. The specific heat exhibits a characteristic double peak as a function of an applied magnetic field which cannot be accounted for by the spin wave approximation. This illustrates the importance of non-linearity for the thermodynamics of quantum spin chains even at low temperature.

Carlos Mejía-Monasterio, Hannu Christian Wichterich

Yonghong Yan, Qifeng Liang, Hui Zhao