Role of Anharmonicity in Specific Heat of Metals and Insulators at Low Temperatures

In this paper we discuss the role of anharmonicity of lattice waves in electronic specific heat of metals and insulators at very low temperatures. Previous researchers have revealed the anharmonicity of the lattice waves to cause deviation in specific heat from Debye T3 law. Different researchers have given different concepts of anharmonicity in electronic specific heat of metals at very low temperatures. The energy spectrum of phonons can not be fully described by the Debye law. On the whole all reports dilute the contention of the electronic contribution to be responsible for linear temperature dependent component of specific heat of metals at very low temperatures. For anharmonicity of lattice waves this contribution must be expected for metals and insulators also.

Theory of the strange metal Sr3Ru2O7

The bilayer perovskite Sr3Ru2O7 has been widely studied as a canonical strange metal. It exhibits T-linear resistivity and a T log(1/T) electronic specific heat in a field-tuned quantum critical fan. Criticality is known to occur in “hot” Fermi pockets with a high density of states close to the Fermi energy. We show that while these hot pockets occupy a small fraction of the Brillouin zone, they are responsible for the anomalous transport and thermodynamics of the material. Specifically, a scattering process in which two electrons from the large, “cold” Fermi surfaces scatter into one hot and one cold electron renders the ostensibly noncritical cold fermions a marginal Fermi liquid. From this fact the transport and thermodynamic phase diagram is reproduced in detail. Finally, we show that the same scattering mechanism into hot electrons that are instead localized near a 2D van Hove singularity explains the anomalous transport observed in strained Sr2RuO4.

Impurity-induced tunneling-mediated superconducting gap in bilayer cuprate superconductors

We have proposed a model Hamiltonian describing the interlayer tunneling in d-wave bilayer cuprate superconductors. The Hamiltonian is solved for the quasi-particle energy bands and the superconducting (SC) order parameter by using Zubarev’s technique of double time Green’s functions. The effects of interlayer tunneling and the strength of non-magnetic potential are studied for SC order parameter, density of states (DOS), electronic specific heat and quasi-particle energy bands, and the results are compared with others.