Proximity induced ferromagnetism, superconductivity, and finite-size effects on the surface and edge states of topological insulator nanostructures

Abstract

Bi${}_2$Te${}_3$ and Bi${}_2$Se${}_3$ are well known 3D-topological insulators. Films made of these materials exhibit metal-like surface states with a Dirac dispersion and possess high mobility. The high mobility metal-like surface states can serve as channel material for TI-based field effect transistors. While such a transistor offers superior terminal characteristics, they suffer from an inherent zero band gap problem. The absence of a band gap for the surface states prevents an easy turn-off mechanism. In this work, techniques that can be employed to easily open a band gap for the TI surface states is introduced. Two approaches are described: 1) Coating the surface states with a ferromagnet which has a controllable magnetization axis. The magnetization strength of the ferromagnet is incorporated as an exchange interaction term in the Hamiltonian. 2) An \textit{s}-wave superconductor, because of the proximity effect, when coupled to a 3D-TI opens a band gap on the surface. This TI-superconductor heterostructure is modeled using the Bogoliubov-de Gennes Hamiltonian. A comparison demonstrating the finite size effects on surface states of a 3D-TI and edge states of a CdTe/HgTe/CdTe-based 2D-TI is also presented. 3D-TI nanostructures can be reduced to dimensions as low as 10.0 $\mathrm{nm}$ in contrast to 2D-TI structures which require a thickness of at least 100.0 $\mathrm{nm}$. All calculations are performed using the continuum four-band k.p Hamiltonian.

9 pages,12 figures

References in corpus (8)

• Superconducting proximity effect and Majorana fermions at the surface of a topological insulator
• Topological Insulators with Inversion Symmetry
• Discovery (theoretical prediction and experimental observation) of a large-gap topological-insulator class with spin-polarized single-Dirac-cone on the surface
• Phase transition between the quantum spin Hall and insulator phases in 3D: emergence of a topological gapless phase
• Three dimensional topological invariants for time reversal invariant Hamiltonians and the three dimensional quantum spin Hall effect
• Surface States of the Topological Insulator Bi_{1-x}Sb_x
• Ultra-thin Topological Insulator Bi2Se3 Nanoribbons Exfoliated by Atomic Force Microscopy
• Evidence for Two Gaps and Breakdown of the Uemura Plot in Ba${}_{0.6}$K${}_{0.4}$Fe${}_2$As${}_2$ Single Crystals

Cited by in corpus (1)

• The influence of proximity induced ferromagnetism, superconductivity and Fermi-velocity on evolution of Berry phase in Bi${}_2$Se${}_3$ topological insulator