Superconductivity in Cu Co-Doped SrxBi2Se3 Single Crystals

Effect of Sr Doping on Structural and Transport Properties of Bi2Te3

Search for doped superconducting topological insulators is of prime importance for new quantum technologies. We report on fabrication of Sr-doped Bi2Te3 single crystals. We found that Bridgman grown samples have p-type conductivity in the low 1019 cm−3, high mobility of 4000 cm2V−1s−1, crystal structure independent on nominal dopant content, and no signs of superconductivity. We also studied molecular beam epitaxy grown SrxBi2−xTe3 films on lattice matched (1 1 1) BaF2 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 Bi2Te3 and should be helpful for further design of topological insulator-based superconductors.

Making van der Waals Heterostructures Assembly Accessible to Everyone

Van-der Waals heterostructures assembled from one or few atomic layer thickness crystals are becoming increasingly more popular in condensed matter physics. These structures are assembled using transfer machines, those are based on mask aligners, probe stations or are home-made. For many laboratories it is vital to build a simple, convenient and universal transfer machine. In this paper we discuss the guiding principles for the design of such a machine, review the existing machines and demonstrate our own construction, that is powerful and fast-in-operation. All components of this machine are extremely cheap and can be easily purchased using common online retail services. Moreover, assembling a heterostructure out of exfoliated commercially available hexagonal boron nitride and tungsten diselenide crystals with a pick-up technique and using the microphotolumenescence spectra, we show well-resolved exciton and trion lines, as a results of disorder suppression in WSe2 monolayer. Our results thus show that technology of the two-dimensional materials and heterostructures becomes accessible to anyone.

Anomalous Hall effect in Cu doped Bi2Te3 topological insulator

The angle resolved photo-emission spectroscopy (ARPES) study and magneto-transport properties of Bi2Cu x Te3-x have been investigated. ARPES study indicates the clear existence of surface states in the as-prepared samples. The estimated bandgap from ARPES is found to be ∼5 meV and 16 meV respectively for x = 0.03 and x = 0.15 samples. Presence of larger Cu concentration (x = 0.15) introduces magnetic ordering. Observed non-linearity in the Hall data is due to the existence of anomalous Hall effect which can be attributed to the 2D transport. The observed magneto-transport features might be related to the surface carriers which is confirmed by ARPES study.