研究目的
Investigating the electronic properties of few-layer Bi(110) films modulated by NbSe2 substrate, including the unusual superconducting proximity effect and spatial modulations due to covalent-like quasi-bonds.
研究成果
The electronic structure of Bi(110) films is significantly modulated by the NbSe2 substrate through covalent-like quasi-bonds, leading to thickness-dependent and spatially modulated electronic states. This results in an unusual superconducting proximity effect with a non-monotonic decay behavior. The findings suggest that interfacial couplings can be used to tune electronic properties, with implications for enhancing superconductivity and other quantum phenomena in 2D heterostructures.
研究不足
The study is limited to Bi(110) films on NbSe2 substrates; other orientations or materials may exhibit different behaviors. The experimental conditions (e.g., low temperatures, ultrahigh vacuum) may not be easily scalable for practical applications. The DFT calculations rely on specific approximations (e.g., optB86b-vdW functional), which might not capture all electronic interactions accurately.
1：Experimental Design and Method Selection:
The study combines scanning tunneling microscopy and spectroscopy (STM/STS) with density functional theory (DFT) calculations to investigate the electronic structure and superconducting proximity effect in Bi/NbSe2 heterostructures. STM/STS is used for atomic-scale imaging and spectroscopy, while DFT provides theoretical insights into electronic states and interactions.
2：Sample Selection and Data Sources:
Few-layer Bi(110) films are grown on NbSe2 substrates using molecular beam epitaxy (MBE). High-purity Bi (99.999%) is deposited on cleaved NbSe2 single crystals in ultrahigh vacuum.
3：999%) is deposited on cleaved NbSe2 single crystals in ultrahigh vacuum.
List of Experimental Equipment and Materials:
3. List of Experimental Equipment and Materials: Equipment includes a commercial Unisoku STM system (1300), MBE setup with Knudsen cell, W tips for STM, and computational resources for DFT. Materials include NbSe2 single crystals and Bi source.
4：Experimental Procedures and Operational Workflow:
Bi films are grown at room temperature with a rate of ~1.5 ?/min, post-annealed at 520 K. STM/STS measurements are performed at low temperatures (4.5 K or 0.4 K) using constant-current mode for topography and lock-in technique for spectroscopy. DFT calculations involve geometric optimization and electronic property calculations using VASP with van der Waals corrections.
5：5 ?/min, post-annealed at 520 K. STM/STS measurements are performed at low temperatures (5 K or 4 K) using constant-current mode for topography and lock-in technique for spectroscopy. DFT calculations involve geometric optimization and electronic property calculations using VASP with van der Waals corrections.
Data Analysis Methods:
5. Data Analysis Methods: STS data are analyzed to extract density of states and superconducting gaps, fitted with BCS theory. DFT calculations include LDOS, wavefunction visualization, and differential charge density analysis to interpret experimental results.
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