Superconductivity Below 2.5K in Nb0.25Bi2Se3 Topological Insulator Single Crystal

Abstract

We report crystal growth and below 2.5K superconductivity of Nb 0.25 Bi 2 Se 3 . These crystals are grown by self flux method. The X-ray diffraction (XRD) pattern of as grown crystal flake shows (00l) plane (c-orientation) growth. The Rietveld refinement of crushed crystal powder XRD (PXRD) pattern confirms the phase purity of the studied sample having R-3m space group of rhombohedral crystalline structure. The Raman spectrum of the studied Nb 0.25 Bi 2 Se 3 crystal distinctly shows three well defined vibrational modes in terms of A 1 1g , Eg 2 , A 2 1g at around 72, 129 and 173cm -1 , which are slightly shifted in comparison to pure Bi 2 Se 3 . Magnetization studies in terms of field cooled (FC) and Zero field cooled (ZFC) magnetic susceptibility measurements show the diamagnetic transition (T c onset ) of the compound at around 2.5K and near saturation of the same below around 2.1K. The isothernal magnetization (MH) being taken at 2K, revealed the lower critical field (H c1 ) of around 50Oe and the upper critical field (H c2 ) of 900Oe. It is clear the studied Nb 0.25 Bi 2 Se 3 is a bulk superconductor. The superconducting critical parameters thus calculated viz. the coherence length, upper and lower critical fields and superconducting transition temperature for as grown Nb 0.25 Bi 2 Se 3 single crystal are reported here.

Type-II superconductivity below 4K in Sn0.4Sb0.6

“…TS does show some distinct features such as hosting Majorana fermions [4], which are used in fault tolerant quantum computers [5]. Doping is a well-established method to induce superconductivity in bulk TIs like Bi 2 Se 3 , Bi 2 Te 3 as Bi 2 Se 3 , which care made superconducting by intercalation of Copper (Cu), Niobium (Nb), Strontium (Sr), Thallium (Tl) and Palladium (Pd) [6][7][8][9][10]. There are some binary alloys as well; containing heavy elements such as Bismuth (Bi) that shows topological non trivial behavior due to the presence of intrinsic spin orbit coupling (SOC) in these elements [11][12].…”

Metal doping in topological insulators- a key for tunable generation of terahertz

“…Figure 1 shows the XRD of the flake, exhibiting (0,0,3n) reflections plane with n=1,2,3,4,5, and 6. The crystal has purely oriented in the c-axis with no discernible impurity phases [33]. Comparing the Nb-doped Bi 2 Se 3 crystal XRD with the Bi 2 Se 3 XRD from the previous paper shows that there is an addition of (003) reflection planes.…”

“…The optimal stoichiometric ratio of Nb, Bi, and Se are taken and grind using the mortar pester in the mbraun glove box at argon atmosphere. The sample is then pelletized in the quartz tube and placed in the box furnace at optimized heat treatment, as shown in our previous paper [33]. The synthesized single crystal has been characterized by different techniques such as PXRD and Raman spectroscopy.…”

“…Nb-doped crystal shows the highest superconducting critical temperature, among others. The 0.25 doping spectacles the incredible results as spontaneously breaks the time-reversal symmetry due to the formation of Majorana bound states [28,[31][32][33]. The states are non-Abelian particles and have a potential of topologically protected qubits in quantum computation.…”

Superconductivity with Topological Non-trivial Surface States in NbC

“…Topological Superconductivity in bulk material can be induced either by doping of suitable elements in topological material [12][13][14][15][16] or by applying pressure [17,18]. Apart from these methods, there are some Dirac type-II semimetals which show superconductivity in their intrinsic form [19,20].…”