Superconductivity in Cu Co-Doped SrxBi2Se3 Single Crystals

Abstract

In this study, we grew Cu co-doped single crystals of a topological superconductor candidate SrxBi2Se3, and studied their structural and transport properties. We reveal that the addition of even as small an amount of Cu co-dopant as 0.6 atomic %, completely suppresses superconductivity in SrxBi2Se3. Critical temperature (∼2.7 K) is rather robust with respect to co-doping. We show that Cu systematically increases the electron density and lattice parameters a and c. Our results demonstrate that superconductivity in SrxBi2Se3-based materials is induced by significantly lower Sr doping level x<0.02 than commonly accepted x∼0.06, and it strongly depends on the specific arrangement of Sr atoms in the host matrix. The critical temperature in superconductive Sr-doped Bi2Se3 is shown to be insensitive to carrier density.

Link between superconductivity and a Lifshitz transition in intercalated Bi2Se3

“…In addition, the suggested mean-field picture with very weak dependence of T c on the density is in agreement with the observation of a Hall density independent T c in Cu-codoped Sr x Bi 2 Se 3 crystals [22].…”

“…Increasing the carrier density of Bi 2 Se 3 via Cu intercalation results in a quick expansion of the FS towards the Z point and, eventually, a Lifshitz transition into an open cylindrical-like FS [19]. Interestingly, Sr-intercalated Bi 2 Se 3 is reported to have an order of magnitude smaller carrier concentration than the Cu intercalation while still exhibiting superconductivity with similar critical temperature T c [7,21,22]. This raises two questions: (1) Does Sr x Bi 2 Se 3 have a closed Fermi surface that allows for a 3D topological TRI superconductivity?…”

Lifshitz transition in dirty nematic superconductor

“…[39] the authors state that the superconductivity in doped topological insulators appears along with the Lifshitz transition from closed to open Fermi surface. Open Fermi surface has been observed in different compounds of doped topological insulators with the nematic superconductivity [38,50,51]. In our work, we get that the Lifshitz transition is destructive for the nematic superconductivity.…”

“…Both critical temperature and robustness against the disorder are smaller for the open Fermi surface than for the closed one if the density of states is the same. This connection between the shape of the Fermi surface and superconducting properties can be one of the reasons why the critical temperature in doped topological insulators is insensitive to the carrier density [51].…”

Making van der Waals Heterostructures Assembly Accessible to Everyone

“…The growth and characterization of Sr Bi Se single crystals are described in refs. [ 41 , 42 ]. Contact electrodes were lithographically defined on an oxidized Si wafer using a laser pattern generator Heidelberg PG101.…”