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SUMMARY:Spin-orbit coupling\, superconductivity\, and topological states i
 n Sb2Te3-GeTe-based heterostructures - Dr. Vijay Narayan (University of Ca
 mbridge)
DTSTART:20160215T141500Z
DTEND:20160215T151500Z
UID:TALK64493@talks.cam.ac.uk
CONTACT:Teri Bartlett
DESCRIPTION:Spin-orbit coupling\, superconductivity\, and topological stat
 es Sb2Te3 GeTe-based heterostructures. GeTe is a narrow band gap semicondu
 ctor that goes superconducting at low temperatures and additionally\, due 
 to its non-centrosymmetric unit cell\, has a strong spin-orbit field. Thus
  GeTe is a single-phase material which is very likely to host p-wave super
 conductivity. I will first present magneto-transport measurements on Hall 
 bars of molecular beam epitaxy (MBE)-grown thin films of GeTe [1] which ar
 e on the brink of superconductivity. The experimental data show several no
 vel and intriguing characteristics which arise from the interplay of the s
 pin-orbit field and superconducting correlations. First\, the weak anti-lo
 calisation (WAL) behaviour below ≈ 2 K suggests the role of two-dimensio
 nal (2D) rather than bulk conducting states. Second\, at even lower temper
 atures ≈ 0.3 K the impending superconductivity affects both the longitud
 inal and Hall components of resistivity: the former is seen to deviate fro
 m the Hikami-Larkin-Nagaoka (HLN) form [2]\, and the latter develops a per
 ceptible reduction about zero field. And third\, the in-plane field magnet
 oresistance shows a novel and unexplained hysteretic behaviour\, which van
 ishes at 0.7 K. These data offer new insights into the physics underlying 
 spin-orbit coupled superconductors. The second part of my talk will focus 
 on MBE-grown multilayers of GeTe and the topological insulator Sb2Te3 [3] 
 above the superconducting transition of GeTe. The temperature and magnetic
  field-dependent electrical characteristics of the multilayers strongly su
 ggest that transport is confined to the Sb2Te3-GeTe interfaces. Remarkably
 \, we find that Sb2Te3-GeTe-Sb2Te3 can either have one 2D mode or three de
 pending on the precise layer structure. We present experimental evidence s
 uggesting that the intervening GeTe layer has an important role in decidin
 g the ultimate number of 2D states. Our data suggest\, therefore\, that th
 e GeTe-Sb2Te3 system is a promising platform to realise topological insula
 tor multilayers\, and thus towards explorations of exotic topological phas
 es.\n[1] V. Narayan\, T.-A. Nguyen\, R. Mansell\, D. A. Ritchie and G. Mus
 sler (Phys. Status Solidi – RRL\, 2016 DOI: 10.1002/pssr.201510430\n[2] 
 S. Hikami\, A. I. Larkin\, Y. Nagaoka\, Prog. Theor. Phys. 1980\, 63\, 707
 .\n[3] T.-A. Nguyen\, D. Backes\, A. Singh\, R. Mansell\, C. Barnes\, D. A
 . Ritchie\, G. Mussler\, M. Lanius\, D.Grützmacher and V. Narayan (in pre
 paration).\n\n
LOCATION:Mott Seminar Room (Mott Building Room 531)\, Cavendish Laboratory
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