On the anomalous thermal evolution of the low-temperature, normal-state specific heat of various nonmagnetic intermetallic compounds

TL;DR

This paper investigates the anomalous low-temperature specific heat behavior in nonmagnetic intermetallic compounds, attributing it to density of states anomalies and providing an analytical model that fits experimental data well.

Contribution

It introduces a novel analytical model representing density of states anomalies as delta functions, successfully fitting experimental specific heat data and explaining the thermal anomalies.

Findings

The model reproduces all features of the anomalous thermal evolution.

Fit parameters align with reported values, validating the approach.

Derived relations between parameters agree with experimental results.

Abstract

The low-temperature normal-state specific heat and resistivity curves of various nonmagnetic intermetallic compounds manifest an anomalous thermal evolution. Such an anomaly is exhibited as a break in the slope of the linearized C/T versus T^2 curve and as a drop in the R versus T curve, both at the same T_{\beta}{\gamma}. It is related, not to a thermodynamic phase transition, but to an anomaly in the density of states curves of the phonon or electron subsystems. On representing these two anomalies as additional Dirac-type delta functions, situated respectively at kB.{\theta}_L (for lattice) and kB.{\theta}_E (for electrons), an analytical expression for the total specific heat can be obtained. A least-square fit of this expression to experimental specific heat curves of various compounds reproduced satisfactorily all the features of the anomalous thermal evolution. The obtained fit parameters (in particular the Sommerfeld constant, {\gamma}_{0}, and Debye temperatures, {\theta}_D, compare favorably with the reported values. Furthermore, the analysis shows that (i) (T_{\beta}{\gamma}) / ({\theta}_D) = 0.2(1\pm1/\surd6) and (ii) {\gamma}_{0} {\propto} ({\theta}_D)^2; both relations are in a reasonable agreement with the experimental results. Finally, this analysis (based on the above arguments) justifies the often-used procedure that treats the above anomaly in terms of either a thermal variation of {\theta}_D or an additional Einstein mode.