Conductance oscillations at the interface between a superconductor and the helical edge channel in a narrow HgTe quantum well
A. Kononov+, S. V. Egorov+, N. Titova*, Z. D. Kvon×, N. N. Mikhailov×, S. A. Dvoretsky×, E. V. Deviatov+°
+Institute of Solid State Physics of the RAS, 142432 Chernogolovka, Russia
*Moscow State Pedagogical University, 119991 Moscow, Russia
×Institute of Semiconductor Physics, 630090 Novosibirsk, Russia
°Moscow Institute of Physics and Technology, 141700 Dolgoprudny, Russia
Abstract
We experimentally investigate electron transport through the interface between
a superconductor and the edge of a two-dimensional electron system with band
inversion. The interface is realized as a tunnel NbN side contact to a narrow
8 nm HgTe quantum well. It demonstrates a typical Andreev behavior with finite
conductance within the superconducting gap. Surprisingly, the conductance is
modulated by a number of equally-spaced oscillations. The oscillations are
present only within the superconducting gap and at lowest, below 1 K,
temperatures. The oscillations disappear completely in magnetic fields, normal
to the two-dimensional electron system plane. In contrast, the oscillations'
period is only weakly affected by the highest, up to 14 T, in-plane oriented
magnetic fields. We interpret this behavior as the interference oscillations in
a helical one-dimensional edge channel due to a proximity with a superconductor.