Title: [Joint CQSE & NCTS Seminar] Multiple Andreev-reflection assisted cooling effects in nano-superconducting Josephson junctions
Speaker: Prof. Jeng-Chung Chen (National Tsing Hua University)
Time: Mar. 17, 2023, 14:30-15:30
Place: NCTS Physics Lecture Hall, 4F, Chee-Chun Leung Cosmology Hall, NTU
Online: https://nationaltaiwanuniversity-zbh.my.webex.com/nationaltaiwanuniversity-zbh.my/j.php?MTID=m210715f40b11b5794be46cfbb95824d1

Abstract:
We demonstrate the cooling effect induced by Multiple-Andreev-reflection (MAR) in
the thermal hysteresis of superconducting constrictions near clean and short limit. We
measure the current-voltage ( I-V ) characteristics of single constriction and -SQUID
devices, and observe a series of voltage-step jumps below the gap (). Our analysis shows
that the voltage-steps are signs of the enhancement of superconductivity driven by excess I ;
in particular, a MAR-assisted cooling effect taken place at V  /e. To illustrate the
consequence of the cooling effect, we show the coexistence of normal current mediated by
Andreev quasiparticles and Josephson supercurrent in the dissipative state of a -SQUID
device. Our findings provide an insightful understanding of nonequilibrium quasiparticle
relaxation in mesoscopic superconducting systems and have strong implications for
developing superconducting ballistic devices.

Biography:
2003 Ph.D. in Physics at Purdue University, U.S.A.
2004-2006 Postdoctoral researcher at the University of Tokyo
2006- present Professor, Department of Physics, National Tsing-Hua University