26th Australian Institute of Physics Congress and the Australian and New Zealand Conference on Optics and Photonics

Artificially synthesised topological insulators in engineered semiconductor nanostructures

Not scheduled

20m

Belinda Hutchinson Building (The University of Sydney )

Contributed Oral AIP | Condensed Matter & Materials (CMM)

Speaker

Mikhail Patrashin (Adelaide University)

Description

In this work we explore the possibilities of creating an artificially synthesised topological insulator (TI) with a flat-band quasiparticle spectrum for realising new emergent superconductivity physics, either in the form of the unconventional bulk superconductivity [1] or by interfacing the TI with a conventional superconductor. The TI is synthesised using an engineered semiconductor superlattice (SL) of InAs/GaInSb [2].
Theoretical modelling of the E(k_x, k_y, k_z) band structure is performed using 8-band k•p method to determine the design parameters of InAs/GaInSb SLs, corresponding to the material phases of conventional semiconductor, zero-gap semimetal, and inverted-band topological insulator. We also obtain the constant energy surfaces at different levels of chemical potentials (Fermi energy) and evaluate expected topological states that can be created in these material phases.
The TI candidate structure is based on InAs/Ga_0.69In_0.31Sb SL with an engineered bulk energy gap of 15-20 meV. It has been fabricated by molecular beam epitaxy (MBE) on GaSb (100) substrate. When optimised, this growth technique preserves the rotational symmetries of the crystal lattice along the growth direction and ensures that the topological states existing between the TI bulk material and interfacial layers or vacuum are topologically protected.
We also report on magnetoresistance (R_xx) and Hall resistance (R_xy) measurements of this structure, demonstrating metallic-like temperature dependence of the resistivity below T<30K, non-saturating R_xx, and Shubnikov–de Haas magneto-oscillations of multiple quasiparticle species attributed to the bulk and surface states.

[1] G. Goldstein, C.Aron, and C Chamon, “Band edge superconductivity”, Phys. Rev. B 92, 020504 (2015)
[2] M. Patrashin, N. Sekine, K. Akahane, A. Kasamatsu and I. Hosako, “Dirac semimetal states in engineered zero-gap InAs/GaInSb superlattices”, Physica Status Solidi B 256(6), 1800726 (2019)
[3] M. Patrashin, K. Akahane, N. Sekine, I. Hosako, “Molecular beam epitaxy of strained-layer InAs/GaInSb superlattices for long-wavelength photodetectors”, J. Cryst. Growth 477, 86–90 (2017)