# 18th International Workshop on Low Temperature Detectors (LTD-18)

22-26 July 2019
Milano
Europe/Rome timezone

## Determination of depairing current of superconducting thin films by means of superconducting nanowire resonators

23 Jul 2019, 17:45
1h 15m
Piazza Città di Lombardia (Milano)

### Piazza Città di Lombardia

#### Milano

Piazza Città di Lombardia, 1, 20124 Milano MI
Poster Low Temperature Detector Development and Physics

### Speaker

Simone Frasca (EPFL)

### Description

We estimate the depairing current of superconducting nanowire single-photon detectors$^1$ (SNSPDs) by studying the dependence of the kinetic inductance on the bias current. The kinetic inductance is determined by measuring the microwave resonance frequency of resonator-style nanowires$^2$. Bias current dependent shifts in the measured resonant frequency correspond to a change in the kinetic inductance, which can be compared to theoretical predictions. We demonstrate that the fast relaxation model$^3$ described in the literature accurately matches the experimental data, as expected based on the short relaxation time of the superconductor compared to the resonant frequencies of the test devices. This method provides a valuable tool for directly determining the depairing current, since it minimizes reliance on externally measured values. Accurate measurement of the depairing current is extremely useful both for theoretically understanding the detection mechanism in SNSPDs and for estimating the quality of the fabricated nanowires and, ultimately, the yield of potentially large arrays. Finally, experiments show that the accessible fraction of the depairing current, namely the so-called constriction factor$^4$ C which is the ratio between the switching and depairing currents, decreases with increasing temperature.
1- G.N. Gol’Tsman et al., “Picosecond superconducting single-photon optical detector”, Appl. Phys. Lett. vol.79, p: 705 (2001)
2- D. F. Santavicca et al., “Microwave dynamics of high aspect ratio superconducting nanowires studied using self-resonance”, J. Appl. Phys. 119, 234302 (2016)
3- J. R. Clem and V. G. Kogan, “Kinetic impedance and depairing in thin and narrow superconducting films”, Phys. Rev. B vol.86, 174521 (2012)
4- A. J. Kerman et al., “Constriction-limited detection efficiency of superconducting nanowire single-photon detectors”, Appl. Phys. Lett. 90, 101110 (2007)

Student (Ph.D., M.Sc. or B.Sc.) Y Y

### Primary authors

Simone Frasca (EPFL) B. A. Korzh (Jet Propulsion Laboratory, California Institute of Technology, Pasadena, California 91101, USA) Marco Colangelo (Massachusetts Institute of Technology) D. Zhu (Department of Electrical Engineering and Computer Science, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA) J. P. Allmaras (Jet Propulsion Laboratory, California Institute of Technology, Pasadena, California 91101, USA) E. E. Wollman (Jet Propulsion Laboratory, California Institute of Technology, Pasadena, California 91101, USA) E. Ramirez (Jet Propulsion Laboratory, California Institute of Technology, Pasadena, California 91101, USA) Dr Andrew Beyer (Jet Propulsion Laboratory) Adriana Lita (National Institute of Standards and Technology (NIST)) Varun Verma (National Institute of Standards and Technology) Sae Woo Nam (National Institute of Standards and Technology) A. G. Kozorezov (Department of Physics, Lancaster University, Lancaster, UK, LA1 4YB) E. Charbon (Advanced Quantum Architectures Laboratory (AQUA), EPFL at Microcity, Rue de la Maladière 71b, CH-2002 Neuchâtel 2, Switzerland) M. D. Shaw (Jet Propulsion Laboratory, California Institute of Technology, Pasadena, California 91101, USA) Prof. Karl K. Berggren (Massachusetts Institute of Technology)