Robust weak antilocalization due to spin-orbital entanglement in Dirac material Sr3SnO

Abstract

The presence of both inversion (P ) and time-reversal (T ) symmetries in solids leads to well-known double degeneracy of electronic bands (Kramers degeneracy). When the degeneracy is lifted, spin textures can be directly observed in momentum space, as in topological insulators or in strong Rashba materials. The existence of spin textures with Kramers degeneracy, however, is very difficult to observe directly. Here, we use quantum interference measurements combined with first-principle band structure calculations to provide evidence for the existence of hidden entanglement between spin and momentum in antiperovskite-type 3D Dirac material Sr3SnO. We find robust weak antilocalization (WAL) independent of the position of EF, whereas clear signature of weak localization (WL) develops only when EF shifts away from the Dirac node by doping. The observed WAL signal at low doping is fitted using a single interference channel which implies that the different Dirac valleys are mixed by disorder. Notably, this mixing does not suppress WAL, suggesting contrasting interference physics compared to graphene. We identify scattering among axially spin-momentum locked states as a key process that leads to a spin orbital entanglement, giving rise to robust WAL. Our work sheds light on the subtle role of spin and pseudospin when both could contribute to the same quantum effect. arXiv:1806.08712v1 [cond-mat.mes-hall]

Unusual valence state in the antiperovskites Sr3SnO and Sr3PbO revealed by x-ray photoelectron spectroscopy

“…Since the samples reported in this work were grown at different times spanning a two-year period, different growth parameters were used in the course of optimizing film quality (example parameters can be found in Refs. [20,25]). We will not focus on these systematic differences, but instead on the ubiquitous observation of an antiperovskite phase via XPS.…”

“…Following growth, the films were examined in situ using reflection high-energy electron diffraction (RHEED), then transferred in vacuum suitcases (Ferrovac GmbH; pressure range: low 10 −10 mbar) for XPS measurements. We note that other films grown with identical conditions to these ones were capped with Au or Apiezon-N grease in an Ar glove box then characterized by X-ray diffraction (XRD) and/or transport [20,25].…”

“…Experimentally, angle-resolved photoemission spectroscopy [11], magnetotransport [12,13] and nuclear magnetic resonance [14] measurements have probed the possible 3D Dirac nature of the electrons in these compounds. Experiments have also revealed signatures of ferromagnetism arising from oxygen vacancies [15,16], high thermoelectric performance [17], superconductivity arising from Sr vacancies [18,19] and weak antilocalization due to spin-orbital entanglement [20]. The rich electronic properties of the antiperovskites take as their fundamental origin the unusual valence state of B (= Sn, Pb).…”

Signatures of dephasing by mirror-symmetry breaking in weak-antilocalization magnetoresistance across the topological transition in Pb1−xSnxSe

“…Our results, together with those for graphene [14,15], lead to a rather striking conclusion that specific space symmetries can account for an apparent low-temperature saturation of τ φ (T ) determined from WAL MR studies. This finding suggests that hidden spatial-symmetry properties, together with decoherence specific to amorphous solids [37], might have often been responsible for a hitherto mysterious low-temperature saturation of τ φ (T ) observed in many systems [38], including recently studied Dirac materials [35,[39][40][41][42].…”

The structural stability, lattice dynamics, electronic, thermophysical, and mechanical properties of the inverse perovskites A 3 OX: A comparative first‐principles study

“…8 Indeed, antiperovskites have acquired a lot of interest due to their numerous interesting properties such as giant negative thermal expansion, 9,10 superconductivity, 11,12 giant magnetoresistance, 13 magnetocaloric effects 14 and magnetostriction, 15 and other utilities. Recent examples of antiperovskites which have drawn interest during the past decade include Sr 3 SnO, 16 Li 3 OCl, 17 Na 3 OCl, 18,19 Na 3 OBr, 20,21 f-electron antiperovskites, 22 Gd 3 AlX(X = B, N), 23 and organicinorganic hybrid antiperovskites. 3,4,24,25 Recent studies have also pointed out that some inverse nitrides and oxides are potential contenders pertaining to topological crystalline insulators 26 and 3D massless Dirac electron systems.…”