Interplay of spin–orbit coupling and superconducting correlations in germanium telluride thin films

Abstract

There is much current interest in combining superconductivity and spin–orbit coupling in order to induce the topological superconductor phase and associated Majorana‐like quasiparticles which hold great promise towards fault‐tolerant quantum computing. Experimentally these effects have been combined by the proximity‐coupling of super‐conducting leads and high spin–orbit materials such as InSb and InAs, or by controlled Cu‐doping of topological insu‐lators such as Bi2Se3. However, for practical purposes, a single‐phase material which intrinsically displays both these effects is highly desirable. Here we demonstrate coexisting superconducting correlations and spin–orbit coupling in molecular‐beam‐epitaxy‐grown thin films of GeTe. The former is evidenced by a precipitous low‐temperature drop in the electrical resistivity which is quelled by a magnetic field, and the latter manifests as a weak antilocalisation (WAL) cusp in the magnetotransport. Our studies reveal several other intriguing features such as the presence of two‐dimensional rather than bulk transport channels below 2 K, possible signatures of topological superconductivity, and unexpected hysteresis in the magnetotransport. Our work demonstrates GeTe to be a potential host of topological SC and Majorana‐like excitations, and to be a versatile platform to develop quantum information device architectures. (© 2016 The Authors. Phys. Status Solidi RRL published by WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Topological states and phase transitions in Sb2Te3-GeTe multilayers

“…Which then implicates the lower TSM, but raises the question as to what it hybridises with. Recalling that 34 nm thick GeTe harbours two surface states14, our data strongly points in favour of the 2D modes on either side of the 11 nm thick GeTe layer hybridising with each other. This is also consistent with the fact that T1 has only one 2D WAL mode where, as per the previous arguments, the two embedded TSMs hybridise across the 15 nm thick GeTe layer.…”

“…Indeed, within the picture that the band gaps of Sb 2 Te 3 and GeTe conspire to inject charges from the latter to the former, it is evident why superconductivity is not observed in these samples: the superconducting temperature T c of GeTe is a monotonically increasing function of its carrier concentration13 and thus reducing the chemical potential in GeTe, as is achieved when placing it in close proximity to Sb 2 Te 3 , will only further suppress T c . At the typical carrier concentrations obtained in the bare GeTe samples T c  ≈ 0.1 K14, and this essentially precludes the possibility of observing superconductivity at the temperatures our experiments are performed at (≥0.3 K). Yet, the strong variation of ρ xx between the different multilayer structures clearly indicates that GeTe is not playing a passive role in the transport.…”

Spin-resolved electronic structure of ferroelectric α-GeTe and multiferroic Ge1−Mn Te

“…Nonetheless, this overwhelming panel of physical properties might also hide unconventional pairings because the system naturally possesses bulk type-II superconductivity in a non-centrosymmetric lattice arrangement [16,17]. For this reason further experimental effort is made to engineer topologically non-trivial systems based on Ge 1−x Mn x Te by adequate doping in order to optimize material conditions for hosting 'Majorana'-like quasiparticles [18].…”

Thickness dependence of electron-electron interactions in topological p−n junctions

“…Especially the number of 2D states n is of utmost interest, since it can provide evidence of the topological nature of a TI 24,25 . By careful observation of either the WAL or EEI, a value for n can be gained [26][27][28][29][30][31][32][33][34][35][36][37] .…”