Evolution of pair correlation symmetries and supercurrent reversal in tilted Weyl semimetals

Abstract

We study the effective symmetry profiles of superconducting pair correlations and the flow of charge supercurrent in ballistic Weyl semimetal systems with a tilted dispersion relation. Utilizing a microscopic method in the ballistic regime and starting from both opposite-pseudospin and equal-pseudospin phonon-mediated oppositespin electron-electron couplings, we calculate the anomalous Green's function to study various superconducting pair correlations that Weyl semimetal systems may develop. The momentum-space profile reveals that by properly manipulating the parameters of Weyl semimetal systems, including the tilting parameter, the effective symmetry class of even-parity s-wave (odd-parity p-wave) superconducting correlations can be converted into a d-wave ( f -wave) symmetry class that consists of equal-pseudospin and opposite-pseudospin channels. We also find that the supercurrent in a ballistic Weyl Josephson junction can be made to vanish or switch directions, depending on the tilt of the Weyl cones, in addition to the relevant parameters characterizing the Weyl semimetal and junction. We show that inversion symmetry breaking terms introduce transitions that result in the appearance of self-biased current at zero difference between the macroscopic phases of the superconducting segments, creating a ϕ 0 Josephson state. Weyl semimetal systems are shown to offer several experimentally tunable parameters to control the induction of higher harmonics into the current phase relations. arXiv:1906.05382v1 [cond-mat.supr-con]

Josephson effect in graphene bilayers with adjustable relative displacement

“…Further details of the numerical algorithm employed for studying the supercurrent can be found in Refs. [67][68][69][70]. This method agrees well with Gorkov's Green's function approach and also can provide access to the quasiclassical regime where the Fermi energy is the largest energy in the system [67][68][69][70][71][72][73].…”

“…[67][68][69][70]. This method agrees well with Gorkov's Green's function approach and also can provide access to the quasiclassical regime where the Fermi energy is the largest energy in the system [67][68][69][70][71][72][73]. To simplify the calculations, we have ignored the inverse proximity effects and considered a situation where the roughness of the interfaces plays a relatively weak role, which is the experimentally relevant regime [1,2].…”

“…The behavior of the supercurrent is governed by the complicated interplay of lattice symmetry and the actual pairing mechanism. If unconventional odd-parity p-wave and f -wave pairing mechanisms are involved, the combination of an appropriate Zeeman field in a Josephson junction with different p-wave ( f -wave) orientations in superconducting leads (or s-wave electrodes) can result in a self-biased current [67][68][69][70][71][72][73]. The cases considered above do not exhaust all theoretical possibilities for introducing superconductivity in the BLG system, but they serve as illustrative examples for what can take place, while further computations should be guided by experimental systems.…”

Controllable chiral Majorana modes by noncollinear magnetic configuration in a topological Josephson junction

“…The ABS can be experimentally investigated by virtue of the CPR I(φ), which just in turn confirms the presence of the CMMs and their contributions to supercurrent. According to equation (10), we calculate I(φ) by using the Andreev bound energies E(φ) of figures 2(a)-(c), which are shown in figure 3(a) for the three magnetic configurations. The sinusoidal shape with periodicity 2π is no more exhibited for each magnetic configuration.…”

“…The anomalous Josephson effect has emerged in the Josephson junctions based on such materials as black phosphorus and tilted Weyl semimetals [5][6][7][8][9]. The φ 0 state can be leveraged to determine the Majorana fermions, type of spin-orbit coupling, order of spin-orbit coupling (linear or cubic), and pairing symmetries [10][11][12].…”