Knez, IvanDu, Rui-RuiSullivan, Gerard2012-11-082012-11-082012Knez, Ivan, Du, Rui-Rui and Sullivan, Gerard. "Andreev Reflection of Helical Edge Modes in InAs=GaSb Quantum Spin Hall Insulator." <i>Physical Review Letters,</i> 109, (2012) American Physical Society: 186603. http://dx.doi.org/10.1103/PhysRevLett.109.186603.https://hdl.handle.net/1911/68347We 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 ∼2e2/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.engArticle is made available in accordance with the publisher's policy and may be subject to US copyright law. Please refer to the publisher's site for terms of use.Journal articlehttp://dx.doi.org/10.1103/PhysRevLett.109.186603