The specific heat for the asymmetric Anderson model is calculated over a physically relevant temperature range by means of the Bethe-Ansatz method. The effect of a magnetic field on the specific heat is also investigated.

Physical Review LettersNov 21, 198313 citations

Physics Letters A

Low-temperature properties of the asymmetric Anderson model (exact solution) II

Alexei M. Tsvelik, Paul B. Wiegmann

Published May 1, 1982• 30 citations

Publisher

DOI: 10.1016/0375-9601(82)90195-5

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Thermodynamic Properties of the Asymmetric Anderson Model: Specific Heat

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1/2

particle-hole symmetric Anderson model, the NCA results are qualitatively wrong for any temperature, even when the approximation gives the exact threshold exponents of the ionic states. Actually, the NCA solution describes an overscreened Kondo effect, because it is the same as for the two-channel infinite-

U

single-level Anderson model. We explicitly show that the NCA is unable to distinguish between these two very different physical systems, independently of temperature. Using the impurity entropy as an example, we show that the low-temperature values of the NCA entropy for the symmetric case yield the limit ${S}_{\mathrm{imp}}(T=0)\ensuremath{\rightarrow}ln\sqrt{2},$ which corresponds to the zero temperature entropy of the overscreened Kondo model. Similar pathologies are predicted for any other thermodynamic property. On the other hand, we have found that the OCA approach lifts the artificial mapping between the models and restores correct properties of the ground state, for instance, a vanishing entropy at low enough temperatures ${S}_{\mathrm{imp}}(T=0)\ensuremath{\rightarrow}0$. Our results indicate that the very well known NCA should be used with caution close to the symmetric point of the Anderson model.