Extremely weak electron-phonon coupling in Josephson junctions built on InAs on Insulator

Abstract

InAs-on-Insulator (InAsOI) enables an effective superconducting proximity effect and extremely weak electron-phonon (e-ph) coupling, allowing precise electronic-temperature control with minimal power. Using Josephson junction thermometry, we extract sub-Kelvin e-ph coupling parameters, confirming strong thermal decoupling and robust superconducting performance. The combination of weak e-ph interaction and full electrostatic tunability makes InAsOI a powerful platform for coherent caloritronics, ultrasensitive bolometry, single-photon detection, and gate-controlled superconducting thermal circuits.

Figures (1)

• Figure 1: InAsOI as a caloritronic material. (a) Layer structure of InAsOI (b) Scheme of the InAsOI mesa (yellow) with Al Joule heaters (red) and Al JJ leads (blue). The device wiring scheme is also represented. (c) JJ resistance vs bath temperature $T$ showing a transition near the Al critical temperature $T_{Al}\simeq$1.2K. (d) Critical current ($I_c$) of the Josephson junction as a function of bath temperature $T$ for both devices. The solid lines are the best fit of $I_c(T)$ against the model describing long diffusive Josephson junctions in the high‑temperature limit. (e) Temperature responsivity $\alpha$ of the Josephson thermometers, as a function of $T$ for both the devices. (f) Experimental data (scatter plot) and the fit (dashed lines) using \ref{['eq1']} at selected bath temperatures for $T_e$ as a function of the injected power $\dot Q_{h}$. Inset: A scheme of the predominant heat currents flowing through the InAsOI system: $\dot Q_{h}$ is the injected power from the Joule heaters, whereas $\dot Q_{e_ph}$ represents the power dissipated to the InAsOI lattice phonons which we assume to be perfectly coupled to that of the substrate and residing at the temperature of the cryostat. (g)-(h): The value of $\Sigma$ extracted from the fitting procedure as a function of $T$ for device 1 (g) and 2 (h). (i)-(k): The value of $n$ extracted from the fitting procedure as a function of $T$ for device 1 (i) and 2 (j).