Squeezed metallic droplet with tunable Kubo gap and charge injection in transition metal dichalcogenides.

Yuan, Jiaren; Chen, Yuanping; Xie, Yuee; Zhang, Xiaoyu; Rao, Dewei; Guo, Yandong; Yan, Xiaohong; Feng, Yuan Ping et al. · Proc Natl Acad Sci U S A · 2020

basic_science · Level V

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Abstract

Shrinking the size of a bulk metal into nanoscale leads to the discreteness of electronic energy levels, the so-called Kubo gap δ. Renormalization of the electronic properties with a tunable and size-dependent δ renders fascinating photon emission and electron tunneling. In contrast with usual three-dimensional (3D) metal clusters, here we demonstrate that Kubo gap δ can be achieved with a two-dimensional (2D) metallic transition metal dichalcogenide (i.e., 1T'-phase MoTe<sub>2</sub>) nanocluster embedded in a semiconducting polymorph (i.e., 1H-phase MoTe<sub>2</sub>). Such a 1T'/1H MoTe<sub>2</sub> nanodomain resembles a 3D metallic droplet squeezed in a 2D space which shows a strong polarization catastrophe while simultaneously maintaining its bond integrity, which is absent in traditional δ-gapped 3D clusters. The weak screening of the host 2D MoTe<sub>2</sub> leads to photon emission of such pseudometallic systems and a ballistic injection of carriers in the 1T'/1H/1T' homojunctions which may find applications in sensors and 2D reconfigurable devices.