Superconductors specific heat

Such transition is called phase A transition (T = 2.505 mK at the melting pressure) this is a second-order transition, with a specific heat discontinuity more similar to that of normal superconductors than to the 4He A-transition (Fig. 2.11). 

An unexpected concentration dependence is found for the parameter which describes, according to eq. (8), the deviation of the field dependence of the electronic specific heat in the mixed state from the linear law expected (Nohara et al. 1997) for isotropic s-wave superconductors in the dirty limit. The large deviations from this linear y(H) law observed... 

An unexpected concentration dependence is found for the parameter ft which describes, according to Eq. (8), the deviation of the field dependence of the electronic specific heat in the mixed state from the expected linear law (Nohara et al., 1997) for isotropic s-wave superconductors in the dirty limit. The large deviations from this linear y(H) law observed for YNi2B2C become smaller in the quasi-dirty limit, however, they do not completely disappear. It has been pointed out by Lipp et al. (2001) that for intermediate deviations from linearity of y (H), i.e. for = 0.15-0.3, the specific heat data of borocarbides at low magnetic fields can be discussed in the context of the conventional s-wave picture as well as within the... 

It was shown that the temperature dependence of the specific heat of the spin-fluctuations mechanism in cuprate superconductors proportional to square the temperature, which correspond d wave pairing [6,9]... 

Prom the temperature dependence of the dHvA (or SdH) oscillations it is possible to extract the effective cyclotron mass (see Sect. 3.1). Comparisons of the mass obtained by these measurements with values from band-structure calculations, cyclotron resonance and specific-heat measurements are sometimes inconsistent. Whether strong electron-electron or electron-phonon interactions play the dominant role for this discrepancy is still under considerable debate and further studies have to deal with this question. Chapter 4 will review the present-day knowledge of the highly active field of the fermiology of organic superconductors . 

A thermodynamic quantity not very often measured for organic superconductors is the specific heat, C. Usually the crystal sizes are rather small and consequently a high sensitivity of the apparatus is needed. In most experiments, therefore, an assembly of many pieces of material is necessary to gain better resolution. In addition, the jump of C at Tc is expected to be rather small especially for compounds with higher transition temperatures because of the comparatively large lattice contribution to C owing to the low electron density and the low vibrational frequencies. 

Nevertheless, it was quite surprising that in the first specific-heat experiment, the measurement of j8-(ET)2l3 down to 0.7K, no signs of an anomaly at Tc could be found [208]. This apparent contradiction to the Meissner measurements [181] might be due to a spread of Tc. in the samples and a lack of resolution in the measurement. Later C experiments of other ET superconductors could well resolve the jump AC at Tc and a temperature dependence of C in reasonable agreement with BCS theory. FVom some of these experiments, however, a tendency towards strong coupling was concluded [209, 210, 211, 212]. 

ThRe2 exhibits an unexpectedly high y value [28.5 mJ/mol K2 (Ott et al. 1986)]. The occurrence of superconductivity below Tc = 5 K, as reported by Giorgi and Szklarz (1970), was inferred also from specific heat measurements, but the magnitude of ACp at the transition does not reach the value expected for a bulk superconductor (Ott et al. 1986). The susceptibility at higher temperatures is weakly temperature dependent [X300K = 0.3 X 10-8 m3/mol (Brodsky et al. 1978)]. 

AnBe13 compounds. Lattice parameter a type of the ground state (WP denotes a weak paramagnet, S a superconductor, AF an antiferromagnet) and the low-temperature specific heat coefficient y. 

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