Valleytronic topological filters in silicene-like inner-edge systems

Inner edge state with spin and valley degrees of freedom is a promising candidate for designing a dissipationless device due to the topological protection. The central challenge for the application of the inner edge state is to generate and modulate the polarized currents. In this work, we discover a new mechanism to generate fully valley-and spin–valley-polarized current caused by the Bloch wavevector mismatch(BWM). Based on this mechanism, we design some serial-typed inner-edge filters. By using once of the BWM, the coincident states could be divided into transmitted and reflected modes, which can serve as a valley or spin–valley filter. In particular, while with twice of the BWM, the incident current is absolutely reflected to support an off state with a specified valley and spin, which is different from the gap effect.These findings give rise to a new platform for designing valleytronics and spin-valleytronics.

Energy-resolved spin filtering effect and thermoelectric effect in topological-insulator junctions with anisotropic chiral edge states

Topological edge states have crucial applications in the future nano spintronics devices.In this work,circularly polarized light is applied on the zigzag silicene-like nanoribbons resulting in the anisotropic chiral edge modes.An energy-dependent spin filter is designed based on the topological-insulator(TI)junctions with anisotropic chiral edge states.The resonance transmission has been observed in the TI junctions by calculating the local current distributions.And some strong Fabry–Perot resonances are found leading to the sharp transmission peaks.Whereas,the weak and asymmetric resonance corresponds to the broad transmission peaks.In addition,a qualitative relation between the resonant energy separation TR and group velocity vf is derived:TR=πhvf n/L,that indicated TR is proportional to vf and inversely proportional to the length L of the conductor.The different TR between the spin-up and spin-down cases results in the energyresolved spin filtering effect.Moreover,the intensity of the circularly polarized light can modulate the group velocity vf.Thus,the intensity of circularly polarized light,as well as the conductor-length,play very vital roles in designing the energy-dependent spin filter.Since the transmission gap root in the Fabry–Perot resonances,the thermoelectric(TE)property can be enhanced by adjusting the gap.A schedule to enhance the TE performance in the TI-junction is proposed by modulating the electric field(Ez).The TE dependence on Ez in the nanojunction is investigated,where the appropriate Ez leads to a very high spin thermopower and spin figure of merit.These TI junctions have potential usages in the nano spintronics and thermoelectric devices.