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Dynamical solutions of a quantum Heisenberg spin glass model

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Abstract.

We consider quantum-dynamical phenomena in the SU(2), S = 1/2 infinite-range quantum Heisenberg spin glass. For a fermionic generalization of the model we formulate generic dynamical self-consistency equations. Using the Popov-Fedotov trick to eliminate contributions of the non-magnetic fermionic states we study in particular the isotropic model variant on the spin space. Two complementary approximation schemes are applied: one restricts the quantum spin dynamics to a manageable number of Matsubara frequencies while the other employs an expansion in terms of the dynamical local spin susceptibility. We accurately determine the critical temperature T c of the spin glass to paramagnet transition. We find that the dynamical correlations cause an increase of T c by \(2\%\) compared to the result obtained in the spin-static approximation. The specific heat C(T) exhibits a pronounced cusp at T c . Contradictory to other reports we do not observe a maximum in the C(T)-curve above T c .

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Authors and Affiliations

  1. Institut für Theoretische Physik und Astrophysik, Universität Würzburg, 97074, Würzburg, Federal Republic of Germany

    M. Bechmann & R. Oppermann

Authors
  1. M. Bechmann
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  2. R. Oppermann
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Correspondence to M. Bechmann.

Additional information

Received: 13 July 2004, Published online: 5 November 2004

PACS:

75.10.Nr Spin glass and other random models - 75.10.Jm Quantized spin models

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Bechmann, M., Oppermann, R. Dynamical solutions of a quantum Heisenberg spin glass model. Eur. Phys. J. B 41, 525–533 (2004). https://doi.org/10.1140/epjb/e2004-00346-y

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