Correct Brillouin zone and electronic structure of BiPd

Abstract

A promising route to the realization of Majorana fermions is in non-centrosymmetric superconductors, in which spin-orbit-coupling lifts the spin degeneracy of both bulk and surface bands. A detailed assessment of the electronic structure is critical to evaluate their suitability for this through establishing the topological properties of the electronic structure. This requires correct identification of the time-reversal-invariant momenta. One such material is BiPd, a recently rediscovered non-centrosymmetric superconductor which can be grown in large, high-quality single crystals and has been studied by several groups using angular resolved photoemission to establish its surface electronic structure. Many of the published electronic structure studies on this material are based on a reciprocal unit cell which is not the actual Brillouin zone of the material. We show here the consequences of this for the electronic structures and show how the inferred topological nature of the material is affected.

Fermi surface investigation of the noncentrosymmetric superconductor α -PdBi

“…Figure 1 shows a typical torque signal for α-PdBi measured at 40 mK with the magnetic field B applied parallel to c. Note that throughout this paper, we use the P112 1 convention of the space group P2 1 (No. 4), i.e., the screw axis is parallel to c. This is consistent with the definition used by Yaresko et al [28], but different from the convention used by Khan et al [26]. The inset of Fig.…”

“…We chose the local density approximation of Perdew and Wang for the exchange-correlation potential [33]. As shown by Yaresko et al, the correct determination of the band structure requires the primitive unit cell [28]. The structural parameters were set to the room-temperature data reported by Ionov et al [28,34].…”

“…As shown by Yaresko et al, the correct determination of the band structure requires the primitive unit cell [28]. The structural parameters were set to the room-temperature data reported by Ionov et al [28,34]. Altogether, there are eight inequivalent atomic sites in α-PdBi.…”

Surface states in noncentrosymmetric superconductor BiPd

“…Scanning tunneling spectroscopy study [12] shows presence of surface states above the Fermi level also. It has been found [13] that the surface states appearing below the Fermi level are located at , while those appearing above the Fermi level are located at (see figure 1(a)). The Dirac like surface states on (010) surface lie at 0.66 eV binding energy and are imaged clearly in ARPES experiments.…”

Exceptional Dirac states in a non-centrosymmetric superconductor, BiPd

“…Thirupathaiah et al [6] reported this band to be found at Γ (Brillouin zone center). However, Yaresko et al have shown the Dirac states to be positioned at S, a high-symmetry point at the surface Brillouin zone boundary based on their detailed density functional theoretical (DFT) calculations [15]. In addition to this conflicting results on location of the Dirac node, Thirupathaiah et al [6] proposed three dimensional nature of the Dirac states depicted by an energy gap at the Dirac node varying with k z ; although the repetitive nature of the gap as a function of k z was not observed.…”