Topological band crossings in epitaxial strained SnTe

Abstract

Epitaxial SnTe (111) is grown by molecular-beam epitaxy on Bi 2 Te 3 substrates. Structural evaluation indicates that SnTe deviates from cubic due to in-plane compressive strain, which induces significant changes in the electronic band structure. More specifically, a pair of gapless crossings between the two uppermost valence bands occurs in k space along the out-of-plane Z direction of the Brillouin zone, associated with a band inversion, thus defining topological three-dimensional Dirac nodes. Combined first-principles calculations and angle-resolved photoelectron spectroscopy reveal an overtilted Dirac cone indicating that the crossing is a topological type-III Dirac node at the borders between type-I and type-II Dirac nodes.

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“…LaSb [21], TmSb [23], TaAs [24] and YbAs [25] have been shown to become topologically non-trivial with pressure. Topological phase in LaSb [26], and SnTe [27] has also been observed under epitaxial strain and the same has been confirmed experimentally by angle-resolved photoemission spectroscopy (ARPES) in SnTe [27].…”

“…The implementation of molecular beam epitaxy method had successfully shown the presence of epitaxial strain induced during the growth process of rare-earth pnicitides on III-V semiconductors [49]. The III-V semiconductors [26,50] have attained compressive epitaxial strain of up to 3%, and a similar behaviour can be expected from rocksalt rare-earth monopnictides e.g., for LaSb and SnTe, respectively, 1.6% epitaxial and 1.1% out-of-plane tensile strain have been reported previously [26,27]. This induced strain may influence the charge transfer at the interface which can further affect the carrier compensation [26].…”

Type-III Dirac fermions in HfxZr1−xTe2 topological semimetal candidate

“…Zn2In2S5 12 ) could be the solid state (or fermionic) analogue of the black hole event horizon potentially generating "Hawking radiation" at relatively high "Hawking temperature" 2 showing promise for new exotic physics and applications. Although a type-III Dirac crossing was only a theoretical possibility up to now, experimental evidence has been recently obtained in strained epitaxial SnTe, 13 between its two uppermost valence bands, 1.83 eV below the Fermi level using synchrotron ARPES and also in artificial photonic orbital graphene lattices. 14 Prototypical topological Dirac semimetals are 3D crystal structures and are typically grown as bulk crystals, 15,16 usually suffering from heteroepitaxial defects which yield discontinuous films with poor crystalline quality.…”

Thermoelectric transport of type-I, II, and III massless Dirac fermions in two-dimensional lattice model

“…The critical point between the type-I and the type-II is called the type-III Dirac cone, where one of the bands consisting of the Dirac cone has a flat dispersion along a certain direction, resulting in a diverging density of state (DOS) at the Dirac point. Although the type-III Dirac cone is rare compared with the other two types, it has gained attention recently [11][12][13][14][15][16][17][18][19][20][21][22][23][24][25].…”