Charge localization and reentrant superconductivity in a quasi-ballistic InAs nanowire coupled to superconductors

A semiconductor nanowire with strong spin-orbit coupling in proximity to a superconductor is predicted to display Majorana edge states emerging under a properly oriented magnetic field. The experimental investigation of these exotic states requires assessing the one-dimensional (1D) character of the nanowire and understanding the superconducting proximity effect in the presence of a magnetic field. Here, we explore the quasi-ballistic 1D transport regime of an InAs nanowire with Ta contacts. Fine-tuned by means of local gates, the observed plateaus of approximately quantized conductance hide the presence of a localized electron, giving rise to a lurking Coulomb blockade effect and Kondo physics. When Ta becomes superconducting, this local charge causes an unusual, reentrant magnetic field dependence of the supercurrent, which we ascribe to a 0 - p transition. Our results underline the relevant role of unintentional charge localization in the few-channel regime where helical subbands and Majorana quasi-particles are expected to ariseWe acknowledge financial support from the Agence Nationale de la Recherche (TOPONANO project) and from the EU (ERC grant no. 280043). R.A. acknowledges financial support from the Spanish Ministry of Economy and Competitiveness (grant FIS2015-64654-P). R.Ž. acknowledges support from the Slovenian Research Agency (ARRS) under Program P1- 0044 and J1-725

Charge localization and reentrant superconductivity in a quasi-ballistic InAs nanowire coupled to superconductors

[EN] A semiconductor nanowire with strong spin-orbit coupling in proximity to a superconductor is predicted to display Majorana edge states emerging under a properly oriented magnetic field. The experimental investigation of these exotic states requires assessing the one-dimensional (1D) character of the nanowire and understanding the superconducting proximity effect in the presence of a magnetic field. Here, we explore the quasi-ballistic 1D transport regime of an InAs nanowire with Ta contacts. Fine-tuned by means of local gates, the observed plateaus of approximately quantized conductance hide the presence of a localized electron, giving rise to a lurking Coulomb blockade effect and Kondo physics. When Ta becomes superconducting, this local charge causes an unusual, reentrant magnetic field dependence of the supercurrent, which we ascribe to a 0 - p transition. Our results underline the relevant role of unintentional charge localization in the few-channel regime where helical subbands and Majorana quasi-particles are expected to arise.We acknowledge financial support from the Agence Nationale de la Recherche (TOPONANO project) and from the EU (ERC grant no. 280043). R.A. acknowledges financial support from the Spanish Ministry of Economy and Competitiveness (grant FIS2015-64654-P). R.Ž. acknowledges support from the Slovenian Research Agency (ARRS) under Program P1-0044 and J1-7259