We are delighted to announce the upcoming seminar by Dr. Kyung Ho Kim  (Royal Holloway University of London).

 

Date: April 27 (Thu) 11 AM

Place: 1322 Natural Science (No Zoom broadcasting)

Speaker: Dr. Kyung Ho Kim  (Royal Holloway University of London)  

 

Title: Inverse Shapiro steps and coherent quantum phase slip in superconducting nanowires  

 

Abstract:

We observe clearly visible steps at constant currents I=2efn on the current voltage characteristic of a superconducting nanowire with integer n, exposed to microwave of frequency f [1]. These current steps are dual steps to the well-known Shapiro steps in Josephson junctions which are currently used for commercial Josephson voltage standard in quantum metrology. The dual Shapiro step, or inverse Shapiro step, was theoretically predicted more than 30 years ago in Josephson junctions [2], but it was elusive for the experimentalists due to challenges of circuit engineering. Superconducting nanowires are another system that is predicted to show the dual Shapiro steps due to the coherent quantum phase slip [3]. We embed a superconducting nanowire in an appropriate electromagnetic environment. The inverse Shapiro step is exceedingly promising for closing the so-called quantum metrology triangle as the voltage standard is based on the usual Shapiro steps. I will discuss physics of QPS in superconducting nanowires and condition for the observation of the current quantization.  

 

[1] Shaikhaidarov, R.S., Kim, K.H., Dunstan, J.W. et al. Nature 608, 45–49 (2022) 

[2] Averin, D.V., Zorin, A.B., Likharev, K.K.: Bloch oscillations in small Josephson junctions. Soviet Physics - JETP 61(2), 407 (1985) 

[3] Mooij, J.E., Nazarov, Y.V.: Superconducting nanowires as quantum phase-slip junctions. Nature Physics 2(3), 169 (2006)