Condensed Matter Experiment Seminar - Pratap Raychaudhuri (Tata Institute of Fundamental Research), "Emergence of nanoscale inhomogeneity and the pseudogap state in a homogeneously disordered s-wave superconductor"

Pratap Raychaudhuri
February 26, 2015
11:30AM - 12:30PM
Smith Seminar Room (1080 PRB)

Date Range
2015-02-26 11:30:00 2015-02-26 12:30:00 Condensed Matter Experiment Seminar - Pratap Raychaudhuri (Tata Institute of Fundamental Research), "Emergence of nanoscale inhomogeneity and the pseudogap state in a homogeneously disordered s-wave superconductor" The notion of spontaneous formation of an inhomogeneous superconducting state is at the heart of most theories attempting to understand the superconducting state in the presence of strong disorder. Using a combination of scanning tunneling spectroscopy and high resolution scanning transmission electron microscopy, we experimentally demonstrate that under the competing effects of strong homogeneous disorder and superconducting correlations, the superconducting state of a conventional superconductor, NbN, spontaneously segregates into domains. Tracking these domains as a function of temperature we observe that the superconducting domains persist across the bulk superconducting transition, Tc, and disappear close to the pseudogap temperature, T*, where signatures of superconducting correlations disappear from the tunneling spectrum and the superfluid response of the system. These results along with complementary measurements of the superfluid stiffness at microwave frequencies underpin the importance of phase fluctuations in strongly disordered s-wave superconductors. References: Emergence of nanoscale inhomogeneity in the superconducting state of a homogeneously disordered conventional superconductor Anand Kamlapure, Tanmay Das, Somesh Chandra Ganguli, Jayesh B. Parmar, Somnath Bhattacharyya and Pratap Raychaudhuri Scientific Reports 3, 2979 (2013). Enhancement of the finite-frequency superfluid response in the pseudogap regime of strongly disordered superconducting films Mintu Mondal, Anand Kamlapure, Somesh Chandra Ganguli, John Jesudasan, Vivas Bagwe, Lara Benfatto and Pratap Raychaudhuri Scientific Reports 3, 1357 (2013). Phase diagram of a strongly disordered s-wave superconductor, NbN, close to the metal-insulator transition Madhavi Chand, Garima Saraswat, Anand Kamlapure, Mintu Mondal, Sanjeev Kumar, John Jesudasan, Vivas Bagwe, Lara Benfatto, Vikram Tripathi and Pratap Raychaudhuri Phys. Rev. B 85, 014508 (2012).  Phase fluctuations in a strongly disordered s-wave NbN superconductor close to the metal-insulator transition Mintu Mondal, Anand Kamlapure, Madhavi Chand, Garima Saraswat, Sanjeev Kumar, John Jesudasan, L. Benfatto, Vikram Tripathi and Pratap Raychaudhuri Phys. Rev. Lett. 106, 047001 (2011). Smith Seminar Room (1080 PRB) America/New_York public

The notion of spontaneous formation of an inhomogeneous superconducting state is at the heart of most theories attempting to understand the superconducting state in the presence of strong disorder. Using a combination of scanning tunneling spectroscopy and high resolution scanning transmission electron microscopy, we experimentally demonstrate that under the competing effects of strong homogeneous disorder and superconducting correlations, the superconducting state of a conventional superconductor, NbN, spontaneously segregates into domains. Tracking these domains as a function of temperature we observe that the superconducting domains persist across the bulk superconducting transition, Tc, and disappear close to the pseudogap temperature, T*, where signatures of superconducting correlations disappear from the tunneling spectrum and the superfluid response of the system. These results along with complementary measurements of the superfluid stiffness at microwave frequencies underpin the importance of phase fluctuations in strongly disordered s-wave superconductors.

References:

Emergence of nanoscale inhomogeneity in the superconducting state of a homogeneously disordered conventional superconductor

Anand Kamlapure, Tanmay Das, Somesh Chandra Ganguli, Jayesh B. Parmar, Somnath Bhattacharyya and Pratap Raychaudhuri

Scientific Reports 3, 2979 (2013).

Enhancement of the finite-frequency superfluid response in the pseudogap regime of strongly disordered superconducting films

Mintu Mondal, Anand Kamlapure, Somesh Chandra Ganguli, John Jesudasan, Vivas Bagwe, Lara Benfatto and Pratap Raychaudhuri

Scientific Reports 3, 1357 (2013).

Phase diagram of a strongly disordered s-wave superconductor, NbN, close to the metal-insulator transition

Madhavi Chand, Garima Saraswat, Anand Kamlapure, Mintu Mondal, Sanjeev Kumar, John Jesudasan, Vivas Bagwe, Lara Benfatto, Vikram Tripathi and Pratap Raychaudhuri

Phys. Rev. B 85, 014508 (2012). 

Phase fluctuations in a strongly disordered s-wave NbN superconductor close to the metal-insulator transition

Mintu Mondal, Anand Kamlapure, Madhavi Chand, Garima Saraswat, Sanjeev Kumar, John Jesudasan, L. Benfatto, Vikram Tripathi and Pratap Raychaudhuri

Phys. Rev. Lett. 106, 047001 (2011).