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Temperature Effects on the Electronic Structures of Epitaxial 1T'-WSe2 Monolayers
Wang Chen1, Mengli Hu2, Junyu Zong1
1National Laboratory of Solid State Microstructure, School of Physics, Nanjing University, Nanjing 210093, China.
The Journal of Physical Chemistry Letters
|February 21, 2025
Summary
Epitaxial 1T'-WSe2 monolayers on bilayer graphene show thermal expansion, while those on SrTiO3 remain stable. A Coulomb gap persists up to 200 K, enabling high-temperature quantum spin Hall devices.
Area of Science:
- Condensed Matter Physics
- Materials Science
- Quantum Computing
Background:
- Two-dimensional topological insulators (2D TIs) with a 1T' structural phase, such as transition metal dichalcogenides (TMDCs), are promising for electronic applications.
- Existing research on 1T'-WTe2 shows quantized edge conductance up to 100 K, but higher operating temperatures are needed for industrial use.
- Understanding temperature effects on 1T'-TMDCs is crucial for advancing their technological potential.
Purpose of the Study:
- To investigate the crystal and electronic properties of epitaxial 1T'-WSe2 monolayers grown on bilayer graphene (BLG) and SrTiO3(100) substrates at various temperatures.
- To analyze the impact of different substrates on the thermal expansion and electronic properties of 1T'-WSe2.
- To explore the temperature dependence of the Coulomb gap (CG) and its implications for quantum spin Hall devices.
Main Methods:
- Epitaxial growth of 1T'-WSe2 monolayers on bilayer graphene (BLG) and SrTiO3(100) substrates.
- Temperature-dependent characterization using angle-resolved photoemission spectroscopy (ARPES) and scanning tunneling spectroscopy (STS).
- Monte Carlo simulations to model Coulomb gap behavior.
Main Results:
- 1T'-WSe2/BLG exhibited significant thermal expansion (∼60 × 10-6 K-1), while 1T'-WSe2/SrTiO3 showed minimal changes due to substrate-induced stress.
- A significant Coulomb gap (CG) was observed at the Fermi level for both substrates, with varying sizes influenced by dielectric environment and doping.
- The CG decreased with increasing temperature, persisting up to 200 K for 1T'-WSe2/BLG, consistent with simulations.
Conclusions:
- Epitaxial 1T'-WSe2 monolayers display distinct temperature-dependent behaviors based on substrate choice.
- The observation of a high-temperature persistent Coulomb gap is a key finding for spintronic applications.
- These findings highlight the potential of 1T'-WSe2 for realizing high-temperature quantum spin Hall devices and topological computing.
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