Controllable synthesis and tunable properties of topological material WTe<sub>2</sub>

Abstract

<p indent=0mm>The two-dimensional topological insulator is expected to exhibit the quantum spin Hall effect because of the topologically protected helical edge state. The topological superconductor becomes one of the major material candidates for topological quantum computation due to the existence of Majorana zero-energy mode obeying non-Abelian statistics. Both two-dimensional topological insulator (2DTI) and topological superconductor (TS) can be realized in the monolayer (for 2DTI) or bulk (for TS) WTe₂. Using molecular beam epitaxy, we were able to grow a high-quality 1<italic>T</italic>′-WTe₂ monolayer. We revealed its semimetallic electron band structures using scanning tunneling microscopy/spectroscopy, an insulating phase with a fully opened energy gap is driven in the epitaxial 1<italic>T</italic>′-WTe₂ monolayer that is still topological nontrivial. Under ambient pressure, we performed alkali (K atoms) intercalation to dope electrons and achieved superconductivity transition in bulk Td-WTe₂ (type II Weyl semimetal). The intercalation of K atoms results in a negligible change in the crystal structure of Td-WTe₂, implying that superconductivity in intercalated Td-WTe₂ is still topologically nontrivial, according to X-ray diffraction characterizations.