Switching current distributions in InAs nanowire Josephson junctions

Abstract

We report on the switching current distributions in nano-hybrid Josephson junctions made of InAs semiconductor nanowires. Temperature dependence of the switching current distribution can be understood by motion of Josephson phase particle escaping from a tilted washboard potential, fitted well to the macroscopic quantum tunneling, thermal activation and phase diffusion models, depending on temperature. Application of gate voltage to tune the Josephson coupling strength enables us to adjust the effective temperature for the escaping process, which would be promising for developing gate-tunable superconducting phase qubits. Furthermore, the nano-hybrid JJs provide a useful platform to observe Majorana fermions [8,9] and to develop a gate-tunable transmon qubit, [10] [11] which would be promising for realizing a protectable and scalable qubit.The supercurrent switching event in a current-biased Josephson junction is equivalent to an escaping motion of a Josephson phase particle in a tilted washboard potential [12] determined by the Josephson potential and the bias current, which is given by U(φ) = -E J0 [cos(φ)+(I/I C0 )]. Here, φ is the phase difference across the junction, I C0 is the fluctuationfree switching current, and E J0 = ħI C0 /2e is the Josephson coupling strength. It is well known that the phase particle can escape from the potential well via macroscopic quantum tunneling In this paper, we report on the stochastic switching current distribution in InAs nanowire (NW) JJ. The switching current distributions in the NW JJ were obtained with varying temperature and gate voltage. The escape rate of a phase particle was numerically obtained from the switching current distribution data and fitted well by an appropriate theoretical model. The effective escape temperature T esc of phase particle was also obtained by fitting the switching current distribution to the escape model, confirming the validity of the fitting results. Application of gate voltage induces change of T esc , indicating a gatetunable T esc . We believe that our observations provide useful information for developing nano-hybrid phase qubit based on semiconducting nanowires.InAs NWs were grown via a catalytic process by using vapor-liquid-solid mechanism [4]. After the NWs were transferred to a highly p-doped silicon substrate covered with 250 nm-thick oxide layer, e-beam evaporation of Ti(10 nm)/Al(120 nm) and e-beam lithography were followed to form metallic electrodes. Before metal deposition, the NW surface was deoxidized using buffered hydrofluoric acid for 6 s to ensure transparent contacts.Scanning electron microscope (SEM) image of a typical NW device is shown in the inset of [19,20]. Since the dissipation power is very low (P Joule ~ 4 pW), the self-heating effect is ruled out to explain the hysteresis.The effective capacitance is given by C eff = ħ/R N E Th , where ħ is the Planck's constant divided by 2π, R N (~ 330 Ω) is the normal-state resistance of the junction and E Th is the Thouless energy. Since E Th ~ 0.1 meV (will ...

Two-band induced superconductivity in single-layer graphene and topological insulator bismuth selenide

“…Al/InAs/Al; L=30, 170 nm. The Al/InAs nanowire/ Al junction system has been studied extensively [39,[43][44][45]. From a variety of available I c (sf, T) datasets we present in figures 2(a) and (b) the two most rich datasets and their corresponding fits for Al/InAs/Al junctions with lengths of L=30 nm and L=170 nm reported by Abay et al [39] in their figure 8.…”

Macroscopic Quantum Tunneling in Superconducting Junctions of β-Ag2Se Topological Insulator Nanowire

“…The normalized standard deviation (SD) of each distribution allows us to qualitatively distinguish three regimes of the I C switching process. , Below T = 0.7 K, the SD is nearly temperature independent, indicating that the I C switching is governed by the MQT process. , For 0.7 K < T < 1.1 K, the SD is proportional to temperature, which is due to the TA process . Above 1.1 K, the SD decreases when temperature increases, and this can be explained by the PD process. , A similar temperature dependence of the SD has already been observed in other nanohybrid JJs using graphene , and semiconductor nanowires. , We have reported the first experimental observations of the MQT behavior from TI-based JJs, and the observed MQT temperature, T * MQT , has the highest value among the nanohybrid JJs. The physical origin of the highest T * MQT will be discussed later.…”

“…24,25 A similar temperature dependence of the SD has already been observed in other nanohybrid JJs using graphene 31,32 and semiconductor nanowires. 33,40 We have reported the first experimental observations of the MQT behavior from TI-based JJs, and the observed MQT temperature, T * MQT , has the highest value among the nano-hybrid JJs. The physical origin of the highest T * MQT will be discussed later.…”

“…In particular, observation of the MQT provides direct evidence for the quantum nature of the JJ, which is essential for developing superconducting quantum information devices. 26 In contrast to conventional tunnel-type JJs, 27 nano-hybrid JJs made of semiconducting nanostructures [28][29][30] can be used to introduce an additional control knob to tune the MQT behavior through the gatetunable I C , which has been demonstrated using graphene 31,32 and InAs nanowire 33 (NW). In this work, we report the stochastic switching-current distributions in the MQT regime, obtained from β-Ag 2 Se TI NW-based JJs.…”

“…28 In contrast to conventional tunnel-type JJs, 29 nanohybrid JJs made of semiconducting nanostructures 30−32 which has been demonstrated using graphene 33,34 and InAs NW. 35 In this work, we report the stochastic switching-current distributions in the MQT regime, obtained from β-Ag 2 Se TI NW-based JJs. To the best of our knowledge, the MQT nature inherent in TI JJs is reported for the first time.…”