Flat band transport and Josephson effect through a finite-size sawtooth lattice

TL;DR

This paper theoretically investigates how flat band states in a finite-size sawtooth lattice enhance superfluid transport and Josephson effects, revealing conditions for experimental observation.

Contribution

It demonstrates that flat band states can support larger critical currents and temperatures, with boundary tuning crucial for observing these effects.

Findings

Flat band states support higher critical currents.

Transport reveals geometric contributions of flat band superconductivity.

Boundary tuning is essential for resonance with flat band states.

Abstract

We study theoretically the transport through a finite-size sawtooth lattice coupled to two fermionic reservoirs kept in the superfluid state. We focus on the DC Josephson effect and find that the flat band states of the sawtooth lattice can support larger critical current and at higher temperature than the dispersive band states. However, for this to occur the boundary states of the finite-size lattice need to be tuned at resonance with the bulk flat band states by means of additional boundary potentials. We show that transport in a two-terminal configuration can reveal the salient features of the geometric contribution of flat band superconductivity, namely the linear dependence of key quantities, such as the critical current and critical temperature, on the interaction. Our results are based on parameters of a realistic experimental lattice potential, and we discuss the conditions one needs to reach to observe the predicted effects experimentally.