epitaxial thin films

Transition metal dichalcogenides (TMDs) draw much attention because of their intriguing properties emerging at two-dimensional (2D) limit. Nowadays, some groups have succeeded in exfoliation of metallic TMDs such as NbSe₂ and TaS₂ down to a monolayer limit, unveiling new aspects of 2D physical properties. One remarkable example is unconventional superconductivity achieved by combination of large spin-orbit coupling and broken inversion symmetry, where spin-momentum-locked Cooper pairs play an important role in their superconducting states. Another unique feature is the relationship between superconductivity and charge-density wave (CDW), which has been discussed both in NbSe₂ and TaS₂. In this work, we focus on TaSe₂, which has been also known to have similar electronic structure and exhibit both superconductivity and CDW in its bulk form. There is one paper reporting electronic structure of monolayer TaSe₂ [1], but electrical transport properties of TaSe₂ ultrathin films have not been investigated so far. In this presentation, we report on fabrication of high-quality TaSe₂ thin films by molecular beam epitaxy, and show their transport properties with reduced dimensions.

[1] H. Ryu et al., Nano Lett. 18, 689-694 (2018)