Regensburg 2025 – wissenschaftliches Programm
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TT: Fachverband Tiefe Temperaturen
TT 47: Fluctuations, Noise and Other Transport Topics (joint session TT/DY)
TT 47.10: Vortrag
Donnerstag, 20. März 2025, 17:30–17:45, H31
Josephson force in a vibrating carbon nanotube Josephson junction — •Andreas K. Hüttel1,2, Jukka-Pekka Kaikkonen2, Keijo Korhonen2, and Pertti Hakonen2 — 1Institute for Experimental and Applied Physics, Universität Regensburg, Regensburg, Germany — 2Low Temperature Laboratory, Dept. of Applied Physics, Aalto University, Espoo, Finland
A single carbon nanotube suspended between superconducting electrodes acts simultaneously as nanomechanical resonator and as Josephson junction. Its energy-dependent density of states and thus displacement-dependent Josephson energy couple electronics and mechanics. Measurements on such a system display complex behaviour of the vibrational resonance with respect to junction biasing; strikingly, the resonance frequency decreases in a distinct parameter region where the bias is similar in size to the junction switching current.
We numerically solve the coupled differential equation system of the driven (via an ac gate voltage and an ac bias) system for realistic device parameters, using highly parallelized Julia code, and characterize the evolving steady state. Specific attention is given to the effect of the Josephson junction behaviour on the mechanical resonance frequency and the vibration amplitude. In the numerical results, we observe a clear impact of superconductivity on the mechanical response, with a rather counterintuitive dependence on externally tunable parameters.
Keywords: carbon nanotube; superconductivity; nanomechanics; optomechanics