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arXiv 2001.09777cond-mat.mes-hall
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具有范德华界面的合成半金属

Synthetic Semimetals with van der Waals Interfaces

Bojja Aditya Reddy, Evgeniy Ponomarev, Ignacio Gutiérrez-Lezama, Nicolas Ubrig, Céline Barreteau, Enrico Giannini, Alberto F. Morpurgo

摘要:

适当设计的范德华(vdW)异质结构的组装代表了一种新的方法来生产具有工程电子特性的人工系统。在这里,我们应用这种策略来实现基于由两种不同半导体形成的vdW界面的合成半金属。在已有的从头计算方法的指导下,我们选择WSe $_2$和SnSe $_2$单层和多层膜组装vdW界面,并通过不同的输运实验证明了半金属性的发生.在离子液体门控装置中,当在大范围内扫描门控时,半金属性表现为有限的最小电导,这也提供了能够定量测定带重叠的光谱能力。半金属状态还通过电子和空穴的共存在霍尔效应测量中被揭示,通过观察霍尔斜率随扫描栅极电压或随降低温度的演变来观察。最后,半金属性导致两种本身绝缘的材料的界面的低温金属导电性。这些结果表明,有可能实现一个尚未实现的vdW接口的物质状态,并代表使用这些接口工程拓扑或激子绝缘状态的第一步。

英文摘要:

The assembly of suitably designed van der Waals (vdW) heterostructures represents a new approach to produce artificial systems with engineered electronic properties. Here, we apply this strategy to realize synthetic semimetals based on vdW interfaces formed by two different semiconductors. Guided by existing ab-initio calculations, we select WSe$_2$ and SnSe$_2$ mono and multilayers to assemble vdW interfaces, and demonstrate the occurrence of semimetallicity by means of different transport experiments. Semimetallicity manifests itself in a finite minimum conductance upon sweeping the gate over a large range in ionic liquid gated devices, which also offer spectroscopic capabilities enabling the quantitative determination of the band overlap. The semimetallic state is additionally revealed in Hall effect measurements by the coexistence of electrons and holes, observed by either looking at the evolution of the Hall slope with sweeping the gate voltage or with lowering temperature. Finally, semimetallicity results in the low-temperature metallic conductivity of interfaces of two materials that are themselves insulating. These results demonstrate the possibility to implement a state of matter that had not yet been realized in vdW interfaces, and represent a first step towards using these interfaces to engineer topological or excitonic insulating states.

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