Crystal Field Effect Induced Topological Crystalline Insulators In Monolayer IV-VI Semiconductors

Abstract

Two-dimensional (2D) topological crystalline insulators (TCIs) were recently predicted in thin films of the SnTe class of IV-VI semiconductors, which can host metallic edge states protected by mirror symmetry. As thickness decreases, quantum confinement effect will increase and surpass the inverted gap below a critical thickness, turning TCIs into normal insulators. Surprisingly, based on first-principles calculations, here we demonstrate that (001) monolayers of rocksalt IV-VI semiconductors XY (X=Ge, Sn, Pb and Y= S, Se, Te) are 2D TCIs with the fundamental band gap as large as 260 meV in monolayer PbTe, providing a materials platform for realizing two-dimensional Dirac fermion systems with tunable band gap. This unexpected nontrivial topological phase stems from the strong {\it crystal field effect} in the monolayer, which lifts the degeneracy between $p_{x,y}$ and $p_z$ orbitals and leads to band inversion between cation $p_z$ and anion $p_{x,y}$ orbitals. This crystal field effect induced topological phase offers a new strategy to find and design other atomically thin 2D topological materials.

submitted in Jan. 2015 and published in Nano Lett

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• Towards colloidal spintronics through Rashba spin-orbit interaction in lead sulphide nanosheets
• Topological Zero-Dimensional Defect and Flux States in Three-Dimensional Insulators
• Topological Crystalline Insulator and Quantum Anomalous Hall States in IV-VI based Monolayers and their Quantum Wells
• Two-dimensional Square Buckled Rashba Lead Chalcogenides
• Topological, Valleytronic, and Optical Properties of Monolayer PbS
• Prediction of Topological Crystalline Insulator and Topological Phase Transitions in Two-dimensional PbTe Films
• Spin-orbit insulating phase in SnTe cubic nanowires: consequences on the topological surface states
• Effect of local Coulomb interaction on Majorana corner modes: weak and strong correlation limits
• Surface-dependent Majorana vortex phases in topological crystalline insulators
• Topological electronic structure of twin boundaries and twinning superlattices in the SnTe material class
• Dual topological insulator with mirror symmetry protected helical edge states
• Pentagonal nanowires from topological crystalline insulators: a platform for intrinsic core-shell nanowires and higher-order topology
• Topological phase diagram of Pb1-xSnxSe1-yTey
• Two-atom-thin topological crystalline insulators lacking out of plane inversion symmetry
• Strain-induced two-dimensional topological crystalline insulator
• Non-trivial topological valence bands of common diamond and zinc-blende semiconductors
• Engineering Majorana Kramers Pairs In Synthetic High Spin Chern Insulators
• Tunable Competing Electronic Orders in Double Quantum Spin Hall Superlattices
• Direct observation of the electronic structure of even-layer puckered SnTe monolayer films on graphene