Fermi surface investigation of the noncentrosymmetric superconductor α -PdBi

Abstract

The noncentrosymmetric superconductor α-PdBi is a candidate material for the realization of topological superconductivity. Here, we present a detailed de Haas-van Alphen (dHvA) study together with band-structure calculations within the framework of density functional theory. The rich dHvA spectra are a manifestation of the 13 bands that cross the Fermi energy E F. We find excellent agreement between calculated and experimentally observed dHvA frequencies with moderately enhanced effective masses. One of the bands crossing E F , the so-called α band, exhibits topological character with Weyl nodes lying 43 meV below E F .

Temperature Dependence of the Lower Critical Field of the Noncentrosymmetric Superconductor α‐BiPd

“…Contrary to common belief, a large number of bands crossing the Fermi level (approximately 13 in the case of α-BiPd [7,12,14,20]) does not necessarily promote multiband superconductivity. This is because a variety of interband interactions tend to smear out specific characteristics of singular gaps, and thus give rise to an effective single-gap behaviour [28].…”

“…The superconductivity emerges below a critical temperature T c ≃ 3.8 K at ambient conditions and bears a renewed interest due to strong antisymmetric spin-orbit interaction that generates large Rashba splitting. The latter effect was clearly evidenced experimentally by means of angle-resolved photoemission spectroscopy (ARPES) [7][8][9][10][11] and scanning tunneling spectroscopy [8,12], and confirmed by ab-initio electronic band structure calculations [5,[7][8][9][10][12][13][14]. Furthermore, the spin-resolved ARPES spectra revealed the presence of Dirac surface states [7] that were also inferred from the de Haas -van Alphen oscillations [13,14].…”

“…In other words, the relation 2H c ≃ H c2 found for H k [010] calls for reinterpretation of the field-dependent experiments, which were argued to provide the evidence for multiple superconducting energy gaps in α-BiPd. [16,17,27] Contrary to common belief, a large number of bands crossing the Fermi level (%13 in the case of α-BiPd [7,12,14,20] ) do not necessarily promote multiband superconductivity. This is because a variety of interband interactions tend to smear out specific characteristics of singular gaps, and thus give rise to an effective single-gap behavior.…”

“…The latter effect was clearly evidenced experimentally by means of angle‐resolved photoemission spectroscopy (ARPES) [ 7–11 ] and scanning tunneling spectroscopy, [ 8,12 ] and confirmed by ab initio electronic band structure calculations. [ 5,7–10,12–14 ] Furthermore, the spin‐resolved ARPES spectra revealed the presence of Dirac surface states [ 7 ] that were also inferred from the de Haas–van Alphen oscillations. [ 13,14 ] Odd‐parity order parameter in α ‐BiPd was hypothesized from the Bi nuclear quadrupole resonance study, where strongly reduced coherence peak just below in the spin–lattice relaxation rate was found.…”

“…[ 5,7–10,12–14 ] Furthermore, the spin‐resolved ARPES spectra revealed the presence of Dirac surface states [ 7 ] that were also inferred from the de Haas–van Alphen oscillations. [ 13,14 ] Odd‐parity order parameter in α ‐BiPd was hypothesized from the Bi nuclear quadrupole resonance study, where strongly reduced coherence peak just below in the spin–lattice relaxation rate was found. [ 15 ] Unconventional Cooper paring was also anticipated from the point‐contact Andreev reflection spectra [ 16 ] and the penetration depth data.…”