Spin polarized Charge Trapping and Transfer at a HgTe Topological Insulator Quantum Dot

Abstract: This work presents theoretical demonstration of a carrier trap unit formed by dual topological insulator constrictions (TIC) on the HgTe/CdTe quantum well (QW) with inverted band structures. The sample of HgTe/CdTe QW is patterned into a Hall bar device and a topological quantum dot is created by adding split gate electrodes closely on the QW. In sharp contrast to conventional semiconductor quantum dots, the presence or absence of topological edge states in the proposed quantum hall bar system leads to distinct propagating/insulating state of the TICs with large on/off ratio. This topological quantum dot functions as a carrier trap memory element with near perfect program/erase efficiency by proper adjusting the voltages applied to the split gates. For completeness, we also demonstrate that the Rashba spin orbit interaction in the quantum dot does not destroy the topological edge states and have negligible impact on the conductance of the quantum hall bar. The rapid oscillations in conductance can be suppressed when applying a perpendicular magnetic field in the quantum dot.