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Mapping local superfluid density near the superconductor-insulator transition in NbTiN 


  Anna Kremen [1]  ,  Hasan Khan [2]  ,  Yen Lee Loh [3]  ,  Tatyana .I. Baturina [4,5,1]  ,  Nandini Trivedi [2]  ,  Aviad Frydman [1]  ,  Beena Kalisky [1]  
 [1] Department of Physics, Bar Ilan University, Ramat Gan 52900, Israel
[2] Department of Physics, The Ohio State University, Columbus, OH 43210, USA
[3] Department of Physics and Astrophysics, University of North Dakota, Grand Forks, ND 58202, USA
[4] Institute of Semiconductor Physics, 630090, Novosibirsk, Russia
[5] Novosibirsk State University, Pirogova str. 2, Novosibirsk 630090, Russia


The behavior near the superconductor-insulator transition (SIT) is governed by quantum fluctuations. Direct experimental study of such fluctuations is challenging, and not easily probed by conventional measurements such as transport and magnetoresistance. We use scanning superconductor quantum interference device (SQUID) to simultaneously track magnetometry, susceptometry and local flow of current in a series of TiNbN samples spanning the SIT. Maps of the diamagnetic response provide information about the local superfluid density. Our measurements reveal electronic superconducting granularity which fluctuates in time and space at temperatures well below Tc. The temperature regime of these fluctuations grows as the SIT is approached indicating their quantum nature.