  Proximity effect in a mechanically exfoliated Bi1.95Sb0.05Se3 topological
insulator (TI) single crystal partially covered with disordered superconducting
(SC) Mo thin film is reported. Magnetotransport measurement was performed
simultaneously across three different regions of the sample viz. SC, TI and
SC/TI junction. Resistance measured across SC shows a TC at 4.3 K concomitantly
the resistance measurement on TI showed a metallic trend with a steep upturn at
TC. Magneto-resistance (MR) measurement on TI exhibit a positive MR with
Shubnikov-de Haas (SdH) oscillations, whereas on SC a positive MR superimposed
with steep cusp close to TC is observed. Across SC/TI junction both SdH
oscillation and the cusp were observed. The frequency of SdH oscillation on
SC/TI junction is found to be lesser (~ 125 T) as compared to a reference
Bi1.95Sb0.05Se3sample (~ 174 T). Upper critical field HC2 deduced from WHH fit
was found to be 17.14 T for a reference Mo film whereas Mo film deposited on TI
showed a decreased HC2 of 4.05 T. The coherence length for the former was found
to be 4.38 nm and for the latter 9.01 nm. The interaction between the spin-less
Cooper pairs in SC with the spin-momentum locked carriers on the surface of TI
is believed to cause such changes in transport properties.
