Growth and characterization of high-quality Tl${}_2$Mo${}_6$Se${}_6$ crystals and nanowires

Topological superconductor (TSC) has attracted extensive interest because of its potential application to topological quantum computation, which is based on Majorana fermion (MF). Recently, the long-existed quasi-one-dimensional superconductor, Tl${}_2$Mo${}_6$Se${}_6$, was predicted to be a new TSC. Here we report the growth and characterizations of high-quality superconducting Tl${}_2$Mo${}_6$Se${}_6$ crystals and nanowires. Fiber-shaped crystals with typical size of 0.3$\times$0.3$\times$10 mm${}^3$ were grown by reacting the starting raw materials in a quartz tube. The highest critical temperature (T${}_c$) was observed to be 6.7 K from both resistivity and magnetic susceptibility measurements. The highest shielding fraction was estimated to be 100%. The upper critical field (H${}_{c2}$) behaviour shows an upturn with lowering temperature, which is similar to the results reported before, suggesting unconventional superconductivity. Tl${}_2$Mo${}_6$Se${}_6$ nanowires with typical diameter of 100 nm were obtained by exfoliating Tl${}_2$Mo${}_6$Se${}_6$ crystals, which were used for fabricating devices by e-beam lithography for transport measurements. Superconductivity with T${}_c$ up to 6 K was observed.