Condensed Matter Theory Seminar | June 29, 10:00
Density-induced BCS-Bose evolution in gated two-dimensional superconductors: The role of the interaction range in the Berezinskii-Kosterlitz-Thouless transition
The evolution from Bardeen-Cooper-Schrieffer (BCS) to Bose superconductivity versus carrier density in two-dimensional (2D) gated superconductors is discussed and the fundamental role that the interaction range plays in the Berezinskii-Kosterlitz-Thouless (BKT) transition is addressed. [1]
The density dependence of the critical temperature (Tc), superfluid density, order parameter, chemical potential and pair size is investigated building on earlier work describing the BKT transition from BCS to BEC in 2D superfluids, where an upper bound on Tc was established [2]. The most important finding is that it is essential to include classical and quantum phase fluctuations, as well as finite-ranged interactions, to explain the non-monotonic behavior of Tc versus carrier density and to guarantee that the upper bound on Tc is not exceeded in 2D superconductors [3], as experimentally observed in LixZrNCl, a lithium intercalated layered nitride [4]. Furthermore, it is shown that the effective mass of charge carriers, their interaction strength and range can be extracted from measurements of Tc and the order parameter.
Georgia Institute of Technology, USA
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Contact: Matteo Rizzi