Control of superconducting pairing symmetries in monolayer black phosphorus

Abstract

Motivated by recent experimental progress, we study the effect of mechanical deformations on the superconducting pairing symmetries in monolayer black phosphorus (MBP). Starting with phonon-mediated intervalley spin-singlet electron-electron pairing and making use of realistic band parameters obtained through firstprinciples calculations, we show that the application of weak mechanical strain in the plane of MBP can change the effective s-wave and p-wave symmetry of the superconducting correlations into effective d-wave and fwave symmetries, respectively. This prediction of a change in the pairing symmetries might be experimentally confirmed through angular dependence high-resolution tunneling spectroscopy, the Meissner effect, and critical temperature experiments. The idea of manipulating the superconducting symmetry class by applying planar mechanical strain can be extended to other anisotropic materials as well, and may help in providing important information of the symmetries of the order parameter, perhaps even in some high-Tc superconductors.

Symmetry of superconducting correlations in displaced bilayers of graphene

“…It is worth mentioning that similar theory study as the present paper was conducted for black phosphorus monolayer in Ref. 51. It was found that a significant transition from effective s-wave (p-wave) to d-wave ( f -wave) symmetry class is accessible simply by the exertion of strain into the plane of black phosphorus monolayer.…”

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

“…As recently demonstrated, control of these parameters is possible by, for example, applying strain to the system. [9][10][11] To further shed light on the symmetry profiles of these superconducting correlations, in Figs. 1-3, we present a few representative profiles for the real and imaginary parts of the equal-Pspin and opposite-Pspin components as a function of the momenta k x and k y .…”

“…Such situations can be precisely determined by first-principles calculations; e.g., when the system experiences external strain or is subject to doping and intercalation. A practical example is when a black phosphorus mono- layer is under the application of an external strain, as was recently discussed [9][10][11] . The band-structure parameters were obtained using density-functional-theory computations, and symmetry calculations demonstrated that the momenta coefficients can change sign depending on the strength and direction of the applied in-plane strain.…”

“…4,5 This topological phase results in the band structure in the bulk of Weyl semimetals being gapless, although Fermi arc states connect pairs of Weyl points. [6][7][8][9][10][11] As has been widely discussed, the presence of gapless surface states opens up transport channels free from backscattering. For a conventional type-I WS, the Fermi surface is point-like, where electron and hole states occupy separate energy ranges above or below the Weyl point.…”

“…These intriguing phenomena have motivated a significant wave of interest to the Weyl metal systems both theoretically and experimentally. [7][8][9][10][11]26, When discussing the superconducting state of a Weyl semimetal, the symmetry of the electron-electron coupling potential, ∆, is an important property that gives insight into the nature of the pairing correlations. Moreover, when a relationship exists between the quasiparticle excitations in the Weyl phase and the pair correlations, a more complete understanding of the underlying electronic structure can be obtained.…”