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Dr Thierry Ferrus

Telephone : +44.1223.44.29.35 (Direct)

                    +44.1223.44.29.00 (Secretary)

Email: taf25 (add domain name : "")

Surface states in topological insulators

Hitachi Cambridge Laboratory

Weak antilocalisation effect in Bi2Se3 device in a Hall bar configuration (left). Dependence of the localisation length and the number of conductive channel with temperature (right)

    Topological insulators have the remarkable property that they have an isolated and highly confined surface state at their Fermi energy in certain density ranges depending on material parameters. The electrons or holes propagating in these surface states are subject to strong spin-orbit effects that cause their spin and momentum to be locked perpendicular to one another [1]. In semiconductor field-effect transistors, such properties are only possible at interfaces and in intense magnetic fields. This gives an inherent technological advantage to these materials in producing quantum nanoelectronic devices that could form part of a commercial microelectronic circuit operating in the earth's magnetic field and at room temperature. Spin buses [2] as used in quantum information processing architectures are an example of such a technology.

    Current research is concentrating on three major aspects : the fabrication of devices with strong spin-orbit coupling, THz spectrocopy and transport measurements at low temperatures [3] in partnership with the Thin Film Magnetism Group as well as the Semiconductor Physics Group, both at the Cavendish Laboratory, University of Cambridge.

References :

  1. X. L. Qi, S. C. Zhang, Rev. Mod. Phys. 2011, 83, 1057 (2011) Topological insulators and superconductors
  2. M. Mehring and J. Mende, Phys. Rev. A 73, 052303 (2006) Spin-bus concept of spin quantum computing
  3. V. S. Kamboj, A. Singh, T. Ferrus, H. Beere, T. Hesjedal, C. H. W. Barnes, and D. A. Ritchie, ACS Photonics 4, 11, 2711 (2017), Probing the topological surface states in Bi2Se3 thin films using temperature-dependent terahertz spectroscopy