The Rashba effect and valley polarization provide a novel paradigm in quantum information technology. However, practical materials are scarce. Here, we found a new class of Janus monolayers VXY (X = Cl, Br, I; Y = Se, Te) with excellent valley polarization effect. In particular, Janus VBrSe shows Zeeman type spin splitting of 14 meV, large Berry curvature of 182.73 bohr², and, at the same time, a large Rashba parameter of 176.89 meV·Å. We use the k·p theory to analyze the relationship between the lattice constant and the curvature of the Berry. The Berry curvature can be adjusted by changing the lattice parameter, which will greatly improve the transverse velocities of carriers and promote the efficiency of the valley Hall device. By applying biaxial strain onto VBrSe, we can see that there is a correlation between Berry curvature and lattice constant, which further validates the above theory. All these results provide tantalizing opportunities for efficient spintronics and valleytronics.

中文翻译：

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具有可调大浆果曲率的 Janus VXY 单层膜

Rashba 效应和谷极化为量子信息技术提供了一种新的范例。然而，实用的材料很少。在这里，我们发现了一类新的 Janus 单分子层 VXY（X = Cl、Br、I；Y = Se、Te），具有出色的谷极化效应。特别是，Janus VBrSe 显示出 14 meV 的塞曼型自旋分裂、182.73 bohr ²的大 Berry 曲率，同时具有 176.89 meV·Å 的大 Rashba 参数。我们使用 k·p 理论来分析晶格常数与贝里曲率的关系。通过改变晶格参数可以调节Berry曲率，这将大大提高载流子的横向速度，提高谷霍尔器件的效率。通过对 VBrSe 施加双轴应变，我们可以看到 Berry 曲率与晶格常数之间存在相关性，这进一步验证了上述理论。所有这些结果为高效的自旋电子学和谷电子学提供了诱人的机会。