Manipulating the anomalous Josephson effect by interface valley-polarized mixing

Abstract

We theoretically investigate the supercurrent through a Josephson junction with at least one superconducting electrode directly coupled to a valley-polarized graphene sheet. The anomalous Josephson effect is shown and remarkably manipulated by interface valley-polarized mixing together with combination of the static staggered potentials and off-resonant circularly polarized light field inducing the valley polarization. The unconventional Josephson effect results from the breaking of underlying chiral (polarized-valley rotational) and time-reversal symmetries, which in turn shows the equivalence of the valley and spin freedoms. The valley-polarized interfacetunable phase offset will be of great interest in the designing and fabrication of such novel devices based on valleytronics as superconducting flux-and phase-based quantum bits, phase batteries and rectifiers.

Theoretical valley-polarized subgap transport and intravalley pairing states in a silicene-based antiferromagnet–superconductor junction

“…The bulk-SC electrode directly couples to the silicene layer via a sharp interface, where the sites on each sublattice of the silicene edge connect a bulk SC metal through independent channels. This breaks the coherence between the two different sublattices and brings the valley-mixing scattering at the interface [41][42][43]. As a result, the intravalley AR appears when the AF region is highly valley-polarized.…”

Photoinduced spin-polarized transport and controllable valley-triplet pairing states in a silicene-superconductor junction

“…The left portion indicates the single layer of silicene, where the perpendicular electric field and off-resonant circularly polarized light are applied. The right portion in figure 1(a) indicates a bulk-SC electrode directly coupled to a silicene sheet by means of a sharp interface, where the sites on each sublattice of the silicene edge are coupled to the bulk-SC through independent channels, thus breaking the coherence between the two silicene sublattices and leading to valley-mixing scattering at the interface [22,23,25]. As a result, the valley-triplet AR could occur at the junction interface when the normal silicene region is highly valley-polarized.…”

“…The electrons pair formed from the two opposite valleys is called the valley-single pairing state, a conventional Bardeen-Cooper-Schrieffer (BCS) pairing state [21]. However, it has been predicted that valley-mixing scattering effect at the interface between a graphene sheet and a bulk-SC could lead to a valley-triplet pairing process [22,23], that is, the incident electrons and the reflected holes come from the same valley. These pioneering works were focused on searching for the valleytriplet Josephson current but did not clarify how to probe and control the valley-triplet pairing states.…”

Anomalous thermal phenomena in a temperature biased graphene-based N/I/p-wave SC junction

“…2) Due to the peculiar electronic structure, a variety of unusual electronic transport properties in the graphene-based hybrid structures composed of SCs are revealed. [3][4][5][6][7][8] For example, the anomalous charge conductance and shot noise spectra are exhibited in a graphene-based normal segment (N)/insulator (I)/p-wave SC junction, 6,8) which is ascribed to the low-energy relativistic nature of fermions in graphene. Here, the I region refers to a normal segment of graphene on which an external gate voltage is applied.…”