CdTe作为$\mathbfα$ - Sn/InSb界面隧道势垒的第一性原理评估
First Principles Assessment of CdTe as a Tunnel Barrier at the $\mathbfα$-Sn/InSb Interface
摘要：
Majorana零模在拓扑量子计算中有着广阔的应用前景，有望出现在超导体/半导体界面，如$β$ -Sn和InSb。然而，接近超导体也可能对半导体的局部性质产生不利影响。在接口处插入隧道屏障可以解决这个问题。我们评估的宽带隙半导体，碲化镉，作为一种候选材料，调解之间的晶格匹配的界面耦合$α$ -锡和InSb。为此，我们使用具有Hubbard U校正的密度泛函理论（DFT），其值通过贝叶斯优化（BO）进行机器学习[npj Computational Materials 6，180（2020）]。用角分辨光电子能谱（ARPES）实验对$α$ -Sn和CdTe的DFT+U（BO）结果进行了验证。对于CdTe，使用z-展开方法[Advanced Quantum Technologies，5，2100033（2022）]来解析不同$k_z$值对ARPES的贡献。研究了InSb/ $α$ -Sn、InSb/CdTe、CdTe/ $α$ -Sn双层界面以及InSb/CdTe/$α$-Sn三层界面中金属感生带隙态（MIGS）随CdTe厚度增加的能带偏移和穿透深度。我们发现，16个原子层（3.5 nm）的CdTe可以作为隧道势垒，有效地屏蔽从MIGS从$α$ -Sn的InSb。这可能会指导选择的尺寸的碲化镉屏障调解耦合在超导体-超导体设备在未来的马约拉纳零模式实验。
英文摘要：
Majorana zero modes, with prospective applications in topological quantum computing, are expected to arise in superconductor/semiconductor interfaces, such as $β$-Sn and InSb. However, proximity to the superconductor may also adversely affect the semiconductor's local properties. A tunnel barrier inserted at the interface could resolve this issue. We assess the wide band gap semiconductor, CdTe, as a candidate material to mediate the coupling at the lattice-matched interface between $α$-Sn and InSb. To this end, we use density functional theory (DFT) with Hubbard U corrections, whose values are machine-learned via Bayesian optimization (BO) [npj Computational Materials 6, 180 (2020)]. The results of DFT+U(BO) are validated against angle resolved photoemission spectroscopy (ARPES) experiments for $α$-Sn and CdTe. For CdTe, the z-unfolding method [Advanced Quantum Technologies, 5, 2100033 (2022)] is used to resolve the contributions of different $k_z$ values to the ARPES. We then study the band offsets and the penetration depth of metal-induced gap states (MIGS) in bilayer interfaces of InSb/$α$-Sn, InSb/CdTe, and CdTe/$α$-Sn, as well as in tri-layer interfaces of InSb/CdTe/$α$-Sn with increasing thickness of CdTe. We find that 16 atomic layers (3.5 nm) of CdTe can serve as a tunnel barrier, effectively shielding the InSb from MIGS from the $α$-Sn. This may guide the choice of dimensions of the CdTe barrier to mediate the coupling in semiconductor-superconductor devices in future Majorana zero modes experiments.
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