title: Andreev reflection of helical edge modes in InAs/GaSb quantum spin Hall insulator.
abstract: We present an experimental study of S-N-S junctions, with N being a quantum spin Hall insulator made of InAs/GaSb. A front gate is used to vary the Fermi level into the minigap, where helical edge modes exist [Phys. Rev. Lett. 107, 136603 (2011)]. In this regime we observe a ~2e(2)/h Andreev conductance peak, consistent with a perfect Andreev reflection on the helical edge modes predicted by theories. The peak diminishes under a small applied magnetic field due to the breaking of time-reversal symmetry. This work thus demonstrates the helical property of the edge modes in a quantum spin Hall insulator.
authors.affiliation: Department of Physics and Astronomy, Rice University, Houston, Texas 77251-1892, USA.
authors.forename: Ivan
authors.initials: I
authors.lastname: Knez
authors.forename: Rui-Rui
authors.initials: RR
authors.lastname: Du
authors.forename: Gerard
authors.initials: G
authors.lastname: Sullivan