Topological Phase Transition in the Interaction of Surface Dirac Fermions in Heterostructures

Abstract

Material with a nontrivial topology in its electronic structure enforces the existence of helical Dirac fermionic surface states. We discover emergent topological phases in the stacked structures of topological insulator and band insulator layers where the surface Dirac fermions interact with each other with a particular helicity ordering. Using first-principles calculations and a model Lagrangian, we explicitly demonstrate that such helicity ordering occurs in real materials of ternary chalcogen compounds and determines their topological-insulating phase. Our results reveal the rich collective nature of interacting surface Dirac fermions and pave the way for utilizing topological phases for technological devices such as nonvolatile memories.

Disorder-induced structural transitions in topological insulating Ge-Sb-Te compounds

“…7 First-principles calculations show that crystalline GST compounds can also have a topological insulating phase depending on the composition and layer stacking sequence. [8][9][10] Experimental observation of weak antilocalization in GeSb 2 Te 4 , angle-resolved photoemission study for Ge 2 Sb 2 Te 5 (GST225), and large magneto-resistance in interfacial PCMs supports these theoretical predictions. [11][12][13] GST225 undergoes a series of structural transitions from amorphous to metastable rock-salt structure (or cubic) at $150 C and then to stable hexagonal structure at >300 C. 14 For the hexagonal structure, three types of layer sequencing have been suggested: Petrov sequence Te-Sb-TeGe-Te-Te-Ge-Te-Sb-, 15 Kooi and De Hosson (KH) sequence Te-Ge-Te-Sb-Te-Te-Sb-Ge-, 16 and intermixed sequence TeGe/Sb-Te-Te-Sb/Ge-.…”

Evidence for topological band inversion of the phase change material Ge2Sb2Te5

“…Most notably, a VBM away fromΓ consistently indicates topologically non-trivial properties for GST-225. 18,19,21,29,30 Albeit such a relation is also found for the 3D TIs BiSb…”

OptimizedZTofBi2Te3−GeTecompoun

“…We calculated the electronic structures, using relaxed crystal structures and [24][25][26][27]. As the band dispersion becomes flatter, however, the band gap inversion disappears beyond Ge 3 Bi 2 Te 6 (m = 3, n = 1), which results in minimum !,!…”

“…Theoretically, PbTe-Bi 2 Te 3 (PBT) compounds have been predicted to have larger bandgap energy than Bi 2 Te 3 and improved TE properties with intermediate operating temperatures [23]. Other theoretical studies of these compounds have been focused on their topological properties [24][25][26][27].…”