Collective amplitude mode fluctuations in a flat band superconductor formed at a semimetal surface

V. J. Kauppila; T. Hyart; T. T. Heikkilä

doi:10.1103/PhysRevB.93.024505

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Collective amplitude mode fluctuations in a flat band superconductor formed at a semimetal surface

V. J. Kauppila, T. Hyart, T. T. Heikkilä

DOI 10.1103/PhysRevB.93.024505 · Physical Review B

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Abstract

We study the fluctuations of the amplitude (i.e., the Higgs-Anderson) mode in a superconducting system of coupled Dirac particles proposed as a model for possible surface or interface superconductivity in rhombohedral graphite. This system also serves as a generic model of a topological semimetal with an interaction-driven transition on its surface. We show that the absence of Fermi energy and vanishing of the excitation gap of the collective amplitude mode in the model leads to a large fluctuation contribution to thermodynamic quantities, such as the heat capacity. As a consequence, the mean-field theory becomes inaccurate, indicating that the interactions lead to a strongly correlated state. We also present a microscopic derivation of the Ginzburg-Landau theory corresponding to this model.

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Formula	Reported Tc (K)	Pressure (GPa)	Type
Cu3PdN Archive — visibility unverified Source-occurrence policy only; no material identity or catalogue acceptance is inferred from the formula.	—	Pressure not reported	unknown
Ca3P2 Archive — visibility unverified Source-occurrence policy only; no material identity or catalogue acceptance is inferred from the formula.	—	Pressure not reported	unknown