Abstract
Search for doped superconducting topological insulators is of prime importance for new quantum technologies. We report on fabrication of Sr-doped BiTe single crystals. We found that Bridgman grown samples have p-type conductivity in the low 10 cm, high mobility of 4000 cmVs, crystal structure independent on nominal dopant content, and no signs of superconductivity. We also studied molecular beam epitaxy grown SrBiTe films on lattice matched (1 1 1) BaF polar surface. Contrary to the bulk crystals thin films have n-type conductivity. Carrier concentration, mobility and c-lattice constant demonstrate pronounced dependence on Sr concentration x. Variation of the parameters did not lead to superconductivity. We revealed, that transport and structural parameters are governed by Sr dopants incorporation in randomly inserted Bi bilayers into the parent matrix. Thus, our data shed light on the structural position of dopant in BiTe and should be helpful for further design of topological insulator-based superconductors.
Highlights
Bismuth chalcogenides as topological insulators (TI) and narrow gap semiconductors represent a vast playground for novel physics and applications in the fields of thermoectricity [1], spintronics [2], unusual superconductivity [3], photodetectors [4], optical coatings [5] etc
That transport and structural parameters are governed by Sr dopants incorporation into Bi bilayers between quintuple layers in the parent Bi2Te3 matrix
We revealed a significant bending of the crystalline planes, implying that Sr atoms may be responsible for suppressing layered growth during crystallization, similar to vicinal growth observed for Sr-doped Bi2Se3 bulk crystals [36]
Summary
Bismuth chalcogenides as topological insulators (TI) and narrow gap semiconductors represent a vast playground for novel physics and applications in the fields of thermoectricity [1], spintronics [2], unusual superconductivity [3], photodetectors [4], optical coatings [5] etc. Fundamental interest in search for materials that can display topological superconductivity (TS) is supported by features such as zero bias conduction peak [10,11] and delocalized Andreev bound states [12]. Due to the strong spin–orbit coupling the superconductors derived directly from the topological insulators are promising candidates for TSCs. Binary bismuth-based TIs Bi2Se3 and Bi2Te3 both have tetradymite structure and become superconductors under high pressure [13,14] or due to the proximity effect [15] in close contact of TI with conventional superconductor. Still, doping is more straightforward and flexible approach to achieve superconductivity or to modify transport, optical and magnetic properties of parent TI
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