Effects of defects and dephasing on charge and spin currents in two-dimensional topological insulators

Abstract

Using the non-equilibrium Keldysh Green's function formalism, we investigate the effect of defects on the electronic structure and transport properties of two-dimensional topological insulators (TI).We demonstrate how the spatial flow of charge changes between the topologically protected edge and bulk states and show that elastically and inelastically scattering defects that preserve the time reversal symmetry of the TI lead to qualitatively different effects on the TI's local electronic structure and its transport properties. Moreover, we show that the recently predicted ability to create highly spin-polarized currents by breaking the time-reversal symmetry of the TI via magnetic defects [Phys. Rev. B 93, 081401 (2016)] is robust against the inclusion of a Rashba spin-orbit interaction and the effects of dephasing, and remains unaffected by changes over a wide range of the TI's parameters. We discuss how the sign of the induced spin currents changes under symmetry operations, such as reversal of bias and gate voltages, or spatial reflections. Finally, we show that the insight into the interplay between topology and symmetry of the magnetic defects can be employed for the creation of novel quantum phenomena, such as highly localized magnetic fields inside the TI.

Nontrivial interplay of strong disorder and interactions in quantum spin-Hall insulators doped with dilute magnetic impurities

“…Nevertheless, the connection between the effective 1D models of disorder and the 2D aspects of the physics of QSHIs has not yet been fully investigated to the best of our knowledge. With the exception of a few numerical studies in the non-interacting limit [32,33], there appears to be no systematic investigation about the validity of these 1D models. Indeed, little is known about whether they actually apply in the strong coupling limit where coupling strength to the impurity becomes comparable or larger than the band gap of the QSHI.…”

Atomistic modeling of spin and electron dynamics in two-dimensional magnets switched by two-dimensional topological insulators

“…Therefore, the lower magnetization of the TI results in a lower torque on the 2D FM, causing a delay in transition. The reason for the lower magnetization due to higher J int is because the magnet opens a bandgap in the 2D TI, resulting in a superposition of up and down spins [14]. The superposition of up and down spins in TI leads to a reduced magnetization (For further details, see Supplementary Fig.…”

“…Although there have been some experimental works on realizing magnetic devices using TI-FM interfaces [9][10][11][12], a solid theoretical understanding of the interfacial physics is missing. Most of theoretical works have either investigated equilibrium TI-FM interfaces with a FM having a fixed magnetic orientation [13,14] or investigated the impact of magnetic materials on the topological order of the TIs [15].…”

Conductance fluctuations of monolayer GeSnH2 in the topological phase using a low-energy effective tight-binding Hamiltonian

“…The nonzero conductance in the gap originates from the zero energy edge states and also indicates a topological phase transition from NI to TI in ML GeSnH 2 . These conducting edge states are protected by TRS leading to the robustness of the electronic quantized conductance against backscattering by disorder and therefore holds great promise for spintronics applications [22,23].…”