ISSN:
1434-6036
Source:
Springer Online Journal Archives 1860-2000
Topics:
Physics
Notes:
Abstract Anomalous room-temperature specific heats have been seen experimentally by Knapp and coworkers in highT c superconductors. The measurements depart from 3N k B +γ 0 T by an amount of orderγ 0 T. We present a theory for this, based on the fact that electronphonon interactions cause both electron band energiesε k n and phonon frequenciesω Q µ to be weakly temperature-dependent. First an observation is made which we call Brook's Theorem: the shiftE k n (Q µ) of the electron energyε k n due to adding one phonon in modeQ µ, is identical to the shiftΔΩ Q µ (k n) of the phonon energyω Qµ due to adding one electron in the statek n. Second, we assert that to sufficient accuracy whenT〉Θ D , entropy of the system of interacting electrons and phonons equals the entropy which would be calculated for non-interacting particles, except that theT-dependent energiesE kn (T) andω Q µ (T) should be used. A proof to orderu 2 (whereu is phonon displacement amplitude) was given in the thesis of one of us. Third, we use Brook's Theorem to show that the correctionsΔ C el andΔ C ph to the specific heat due toT-dependence of electron and phonon energies respectively, are identically equal and have order of magnitudeγ 0 T. All these results are valid in adiabatic approximation to orderu 2, and fail at low temperatures where non-adiabatic corrections are large.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/BF01325501
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