Observation of Coulomb gap in the quantum spin Hall candidate single-layer 1T'-WTe${}_2$

Abstract

The two-dimensional topological insulators (2DTI) host a full gap in the bulk band, induced by spin-orbit coupling (SOC) effect, together with the topologically protected gapless edge states. However, the SOC-induced gap is usually small, and it is challenging to suppress the bulk conductance and thus to realize the quantum spin Hall (QSH) effect. In this study, we find a novel mechanism to effectively suppress the bulk conductance. By using the quasiparticle interference (QPI) technique with scanning tunneling spectroscopy (STS), we demonstrate that the QSH candidate single-layer 1T'-WTe${}_2$ has a semi-metal bulk band structure with no full SOC-induced gap. Surprisingly, in this two-dimensional system, we find the electron interactions open a Coulomb gap which is always pinned at the Fermi energy (E${}_F$). The opening of the Coulomb gap can efficiently diminish the bulk state at the E${}_F$ and is in favor of the observation of the quantized conduction of topological edge states.

arXiv comment13 pages, 4 figures

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• Colloquium: Physical properties of group-IV monochalcogenide monolayers
• Observation of Topologically Protected States at Crystalline Phase Boundaries in Single-layer WSe2
• Evidence for equilibrium excitons and exciton condensation in monolayer WTe2
• Strain Tunable Semimetal-Topological-Insulator Transition in Monolayer 1T'-WTe2
• Landau Quantization and Highly Mobile Fermions in an Insulator
• Atomically Thin Quantum Spin Hall Insulators
• Temperature-Induced Lifshitz Transition and Possible Excitonic Instability in ZrSiSe
• The influence of lattice termination on the edge states of the quantum spin Hall insulator monolayer $1T^{\prime }$-WTe${}_2$
• Custodial glide symmetry of quantum spin Hall edge modes in WTe${}_2$ monolayer
• Helical Liquids in Semiconductors
• Electric field effects on the band gap and edge states of monolayer 1T'-WTe2
• Growth and Thermo-driven Crystalline Phase Transition of Metastable Monolayer 1T'-WSe2 Thin Film
• Tunable electronic structure and magnetic anisotropy in bilayer ferromagnetic semiconductor Cr2Ge2Te6
• Hinged Quantum Spin-Hall Effect in Antiferromagnetic Topological Insulators
• Crossover Between Weak Antilocalization and Weak Localization and Electron-Electron Interaction in Few-Layer WTe${}_2$
• Giant periodic pseudo-magnetic fields in strained kagome magnet FeSn epitaxial films on SrTiO${}_3$(111) substrate
• Visualizing symmetry-breaking electronic orders in epitaxial Kagome magnet FeSn films
• Realistic tight-binding model for monolayer transition metal dichalcogenides in 1T' structure
• Room-temperature ferromagnetism in epitaxial bilayer FeSb/SrTiO3(001) terminated with a Kagome lattice
• Quantitative theory of backscattering in topological HgTe and (Hg,Mn)Te quantum wells: acceptor states, Kondo effect, precessional dephasing, and bound magnetic polaron
• A gate-tunable quantum phase transition in a topological excitonic insulator
• Raman spectrum of 1T'-WTe2 under tensile strain: A first-principles prediction
• Reshaped Weyl fermionic dispersions driven by Coulomb interactions in MoTe2
• Theory of Glide Symmetry Protected Helical Edge States in WTe${}_2$ Monolayer
• Low-energy effective theory and anomalous Hall effect in monolayer ${\mathrm{WTe}}_2$
• Emergent $Z_2$ Topological Invariant and Robust Helical Edge States in Two-Dimensional Topological Metals
• Thermal robustness of the quantum spin Hall phase in monolayer WTe${}_2$
• Robust Coulomb Gap and Varied-temperature Study of Epitaxial 1T'-WSe${}_2$ Monolayers
• Electronic properties of the steps in bilayer Td-WTe2
• Observation of quasi-steady dark excitons and gap phase in a doped semiconductor
• Excitonic and magnetic phases in doped WTe${}_2$ monolayers: a Hartree-Fock approach