Kinks in the Electronic Specific Heat

We find that the heat capacity of a strongly correlated metal presents striking changes with respect to Landau Fermi-liquid theory. In contrast with normal metals, where the electronic specific heat is linear at low temperature (with a $T^3$ term as a leading correction), a dynamical mean-field study of the correlated Hubbard model reveals a clear kink in the temperature dependence, marking a rapid change from a low-temperature linear behavior and a second linear regime with a reduced slope. Experiments on ${\mathrm{LiV}}_2{\mathrm{O}}_4$ support our findings, implying that correlated materials are more resistive to cooling at low $T$ than expected from the intermediate temperature behavior.

Figure 1

Kinks in the electronic specific heat (right) for $U/W=0.8$ (upper panel) and 1.0 (lower panel). The left panels show the DMFT(ED) results for the total energy $E_{\mathrm{tot}}$ from which the specific heat has been obtained as a numerical derivative after a spline interpolation. Also shown are two parabolic fits (see text) valid for $T<T^{*}$ (red solid line) and $T>T^{*}$ (violet dotted line) and the DMFT(QMC) results of Ref. 12 (green dots).

Figure 2

Analytical theory describing kinks in the specific heat (red solid line) on the basis of the AGD formula (see text). The blue dashed line in the inset was fitted to the (red) numerical renormalization group data of Ref. [16]; note that the deviation at larger frequencies $\omega$ does not significantly affect the specific heat in the plotted temperature range. The agreement of the analytical calculation with our numerical results (black crosses) is excellent.

Figure 3

Kink in the low-temperature specific heat of ${\mathrm{LiV}}_2{\mathrm{O}}_4$ (open blue circles) visible at $T^{*}\sim 5–6\mathrm{K}$, and well reproduced by our analytical theory (red solid line).