Enhanced Andreev reflection in flat-band systems: Wave packet dynamics, dc transport, and the Josephson effect

Sarbajit Mazumdar; Anamitra Mukherjee; Kush Saha; Sourin Das

doi:10.1103/qr7p-c56y

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Enhanced Andreev reflection in flat-band systems: Wave packet dynamics, dc transport, and the Josephson effect

Sarbajit Mazumdar, Anamitra Mukherjee, Kush Saha, Sourin Das

DOI 10.1103/qr7p-c56y · Physical Review B

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Abstract

We investigate Andreev reflection (AR) in a proximity-induced normal-superconductor (NS) junction within the extended α–T3 lattice, emphasizing the impact of flat bands on AR. Our findings reveal that flat bands significantly enhance AR. Through wave-packet dynamics, we track the real-time evolution of quasiparticle wave packets across the junction, providing deeper insight into electron-hole conversion. Notably, the combination of band flatness and anisotropic dispersion in the kx−ky plane induces an electronic analog of Goos-Hänchen (GH) shifts at the NS interface, exhibiting directional asymmetry along the junction. This asymmetry leads to a Hall-like response in a Josephson junction in the superconductor–normal-metal–superconductor geometry, where transport across the junction region is dominated by the quasiflat bands.