Fig. 1: Principle of Joule spectroscopy.
From: Joule spectroscopy of hybrid superconductor–semiconductor nanodevices
a Schematics of the device geometry. A Josephson junction is formed by etching a 200-nm segment of a full-shell Al-InAs nanowire (NW). Voltage applied to a side gate, Vg, tunes the junction resistance, RJ. The balance between the Joule heat dissipated at the nanowire junction (equal to the product of the voltage, V, and current, I) and the cooling power from the superconducting leads 1 and 2 (P1 and P2) results in a temperature gradient along the device, T(x). At a critical value of Joule dissipation, the temperature of the leads, T0,1 and T0,2, exceed the superconducting critical temperature and the leads turn normal. Each lead can display different superconducting gaps Δ1 and Δ2. An external magnetic field, B, is applied with an angle θ to the NW axis. Tbath is the cryostat temperature. b I (solid black line) and differential conductance, dI/dV (solid blue line), as a function of V measured at Vg = 80 V in device A. For V < 2Δ/e, transport is dominated by Josephson and Andreev processes. By extrapolating the I–V curve just above V = 2Δ/e, an excess current of Iexs ≈ 200 nA is estimated (dashed black line). Upon further increasing V, the Joule-mediated transition of the superconducting leads to the normal state manifests as two dI/dV dips (Vdip,1 and Vdip,2). These transitions fully suppress Iexs (dashed red line). c The nanowire is modeled as a quasi-ballistic conductor with N conduction channels with transmissions τ. We assume that the energy of the quasiparticles injected in the superconductors is fully converted into heat. d Keldysh-Floquet calculations of I(V) and dI/dV(V) using device A parameters (see Supplementary information for more information), reproducing the main features in (b).
