Bi/SiC Material System Promising for Quantum Spin Hall Effect

Bi/SiC Material System Promising for Quantum Spin Hall Effect

PAM-XIAMEN can offer SiC substrate for quantum spin hall effect researches, specifications please refer to https://www.powerwaywafer.com/sic-wafer/sic-wafer-substrate.html.

In quantum spin Hall (QSH) materials, the direction of electron spin is consistent with the direction of motion, making it promising for non dissipative spintronic devices. However, in the currently implemented QSH systems, the maximum bandgap does not exceed 30 meV, so it can only be achieved in extremely low temperature systems. It can only have true practical value at room temperature.

Some researchers point out that although QSH phase itself is a topological phase, other properties in the quantum spin hall system (such as energy gaps) are related to specific materials, specifically spin orbit coupling (SOC) (positively correlated with the fourth power of atomic number Z), orbital hybridization, symmetry, etc. In addition, the influence of the SiC substrate on QSH materials should also be considered. The researchers believe that it is possible to use localized SOC to generate larger energy gaps and achieve room temperature QSH states.

In the experiment, the researchers prepared bismuthene (honeycomb lattice monolayer bismuth, (√ 3 × √ 3) R30 °) on SiC (0001) substrate and confirmed it through ARPES and DFT calculations. Subsequently, the research team used a low-energy efficient model to study the mechanism of energy gap formation near the Fermi level: localized SOC leads to the formation of a band gap at the K point. At the same time, the π bond hybridizes with the SiC substrate, disrupting the mirror symmetry and generating the Rashba effect, causing the degenerate valence band to split near the K point. In addition, the larger lattice constant of SiC substrate also plays a role in the formation of band gaps. Scanning tunneling spectroscopy (STS) shows that its energy gap is about 0.8 eV, and its conduction band edge energy state is consistent with theoretical calculations. The researcher points out that the Bi/SiC material system has the potential to achieve a wide bandgap QSH system, and the next step is to obtain samples with a size of over 25 nm for electrical transport testing.

Fig. 1 Structural model of bismuth on SiC

Fig. 1 Structural model of bismuth on SiC (0001)

Fig. 2 BiSiC Band Structure DFT Calculation and ARPES

Fig. 2 Bi/SiC Band Structure: DFT Calculation and ARPES

Fig. 3 SiC based Bi σ Computational Electronic Structure with Low Energy Efficient Model

Fig. 3 SiC based Bi σ Computational Electronic Structure with Low Energy Efficient Model

Fig. 4 Tunnel spectra of edge states at substrate steps

Fig. 4 Tunnel spectra of edge states at substrate steps

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