Nanofabrication of MISFIT Single Crystals

Most of the crystalline solids are formed by the periodic arrangement of one or more types of atoms in three dimensions following particular spatial symmetries. However, some compounds are treated as two-dimensional because the bonding interactions along one direction is negligible compared to the strong in-plane bonds. Transition metal dichalcogenides constitute a family of two-dimensional compounds where the layers are held together by weak van der Waals (vdW) interactions. One can also artificially stack alternate individual layers of two distinct layered compounds, for example, the so-called MISFIT layered compounds (MLCs). Typically, MLCs can be represented by the general formula [(MX)(1+δ)]m[(TX2)n] with m, n = 1, 2, 3, where M denotes elements such as Sn, Sb, Pb, Bi, rare-earth elements; T represents Ta, Nb, Mo, etc., and X represents chalcogen atoms such as S, Se, Te.1 These compounds resemble the natural vdW heterostructure and consist of alternating layers of distorted rock salt MX and hexagonal TX2 structural units stacked on top of each other. The properties of the MISFIT compounds rely on the charge transfer between the constituent structural units; displaying semiconducting to superconducting behavior.2 The structural scenario can be related to the recent examples of twisted bilayer graphene wherein the electronic structure is substantially modified by moiré superlattice and undergoes superconducting and ferromagnetic transitions.3 The aim of the project is to discover new MISFIT compounds and to investigate the fundamental physical properties of monolayer and multilayers of various MISFIT single crystals in the form of nanodevices. Additionally, there is an immense possibility to tweak the physical properties of these compounds by the use of external perturbations like magnetic and electric fields, uniaxial stress, and strain towards opening up a promising avenue to explore new quantum and topological physics in MISFIT materials.

[1] Radovsky, G.; Popovitz-Biro, R.; Stroppa, D. G.; Houben, L.; Tenne, R.
Nanotubes from Chalcogenide Misfit Compounds: Sn–S and Nb–Pb–S
Acc. Chem. Res. 2014, 47, 406–416
[2] Ng, N.; McQueen, T. M.
Misfit Layered Compounds: Unique, Tunable Heterostructured Materials with Untapped Properties
APL Mater. 2022, 10, 100901
[3] Yankowitz, M.; Chen, S.; Polshyn, H.; Zhang, Y.; Watanabe, K.; Taniguchi, T.; Graf, D.; Young, A. F.; Dean, C. R.
Tuning Superconductivity in Twisted Bilayer Graphene
Science  2019, 363, 1059–1064

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