Tunable spin-polarized edge transport in inverted quantum-well junctions

• Published in: Physical review. B 2017-10, Vol.96 (15), Article 155302
• Main Authors: Nanclares, Dimy, Lima, Leandro R. F., Lewenkopf, Caio H., da Silva, Luis G. G. V. Dias
• Format: Article
• Language: English
• Subjects: Charge transport; Green's functions; Magnetic fields; Quantum wells; Recursive methods; Resistance; Symmetry; Titanium; Topological insulators
• ISSN: 2469-9950; 2469-9969
• DOI: 10.1103/PhysRevB.96.155302

Inverted HgTe/CdTe quantum wells have been used as a platform for the realization of two-dimensional topological insulators, bulk insulator materials with spin-helical metallic edge states protected by time-reversal symmetry. This paper investigates the spectrum and the charge transport in HgTe/CdTe quantum well junctions both in the topological regime and in the absence of time-reversal symmetry. We model the system using the Bernevig-Hughes-Zhang effective Hamiltonian and compute the transport properties using recursive Green's functions with a finite differences' method. Specifically, we have studied the material's spatially resolved conductance in a setup with a gated central region, forming monopolar (n−n′−n) and heteropolar (n−p−n, n-TI-n) double junctions, which have been recently realized in experiments. We find regimes in which the edge states carry spin-polarized currents in the central region even in the presence of a small magnetic field, which breaks time-reversal symmetry. More interestingly, the conductance displays spin-dependent, Fabry-Perót-like oscillations as a function of the central gate voltage producing tunable, fully spin-polarized currents through the device.