Realization of Epitaxial Thin Films of the Topological Crystalline Insulator Sr₃SnO

Abstract

Topological materials are derived from the interplay between symmetry and topology. Advances in topological band theories have led to the prediction that the antiperovskite oxide Sr3SnO is a topological crystalline insulator, a new electronic phase of matter where the conductivity in its (001) crystallographic planes is protected by crystallographic point group symmetries. Realization of this material, however, is challenging. Guided by thermodynamic calculations, a deposition approach is designed and implemented to achieve the adsorption‐controlled growth of epitaxial Sr3SnO single‐crystal films by molecular‐beam epitaxy (MBE). In situ transport and angle‐resolved photoemission spectroscopy measurements reveal the metallic and electronic structure of the as‐grown samples. Compared with conventional MBE, the used synthesis route results in superior sample quality and is readily adapted to other topological systems with antiperovskite structures. The successful realization of thin films of Sr3SnO opens opportunities to manipulate topological states by tuning symmetries via strain engineering and heterostructuring.

Planar Hall effect with sixfold oscillations in a Dirac antiperovskite

“…The residual resistivity ratio (RRR), defined using data points at T = 297 K and 2 K, is roughly 1.7. We note that the temperature dependence and RRR are very similar to Sr 3 SnO films measured using in-situ four-probe transport [36]; therefore, we conclude that no significant degradation was induced by capping our films with grease. 1(e), as well as an additional set of pockets along Γ-M not captured by the effective model [39].…”

“…Previous experiments of Sr 3 SnO have probed its 3D Dirac carriers [34][35][36], observed superconductivity upon hole doping [37] (with possible implications for higher spin Cooper pairing [38]) and detected weak antilocalization (WAL) due to spin-orbital entanglement [39]. Here, we measured the in-plane-field magnetoresistance of thin films of Sr 3 SnO(001) grown by molecular beam epitaxy (MBE) and found them to be a candidate system with an in-plane square lattice exhibiting sixfold oscillations in the PHE.…”

Quantum transport evidence of Weyl fermions in an epitaxial ferromagnetic oxide

“…However, systematic and comprehensive measurements of quantum transport, including the quantum oscillations, have been hampered in magnetic Weyl semimetals because of the difficulty in achieving a quantum lifetime long enough to observe the quantum oscillations in metallic systems. Since specimens in the form of epitaxial films are advantageous for future device applications of magnetic Weyl semimetals, it is urgently required to prepare single-crystalline thin films 27 of magnetic Weyl semimetals whose quality is sufficiently high to probe quantum transport properties.…”

Unusual d-electron heavy-fermion behaviour in f-electron ferromagnetic antiperovskite Gd3SnC

“…In contrast to the perovskite compounds constructed by the ionic bonds of constituent elements in stable valence states, the antiperovskites have mixed bonding characters with ionic, covalent, and metallic bonds in unusual valence states 8 . However, oxide antiperovskites (A 3 BO), antistructures of common oxide perovskites (ABO 3 ), are hardly stabilized in ambient conditions as oxygen tends to form ionic bonds with counter-cationic A and B elements due to its large ionicity 9 . This constraint may be lifted for s-block and transition metal-based antiperovskites, in which additional covalent and metallic bonds come into play for their crystallographic stability 7,10 .…”