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Specific heat of 2H NbSe2

1974; American Institute of Physics; Volume: 45; Issue: 10 Linguagem: Inglês

10.1063/1.1663104

1520-8850

A. J. Bevolo, H. R. Shanks,

Quantum, superfluid, helium dynamics

The specific heats of four samples of 2H NbSe2 have been measured in the temperature range from 1 to 54 K. No anomalous behavior was found near 40 K where x-ray, NMR, and Hall-effect measurements have indicated the presence of a phase transition. An upper limit of 0.3 J/mole K has been placed on the magnitude of any anomaly in the heat capacity associated with this transition. Measurements of high-purity stoichiometric 2H NbSe2 sample gave a superconducting transition temperature of 7.23 K, a specific heat jump (ΔC) in zero field of 240 mJ/mole K, and a Debye temperature of 204 K. A deviation from the usual T3 behavior for the lattice contribution to the heat capacity was observed and assumed to be due to the two-dimensional layer structure of the compound. Our best estimate for the electronic coefficient of specific heat (γ) is about 10±5 mJ/mole K2. Based on the values for Tc and ΔC, the value for γ calculated from BCS theory is 23 mJ/mole K2 for 2H NbSe2 which is in disagreement with our estimated value for γ by a factor of 2.