D. Persson | Chalmers University of Technology (original) (raw)
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Papers by D. Persson
Physical Review B, 2014
We present an extensive experimental and theoretical study of the proximity effect in InAs nanowi... more We present an extensive experimental and theoretical study of the proximity effect in InAs nanowires connected to superconducting electrodes. We fabricated and investigated devices with suspended gate controlled nanowires and non-suspended nanowires, with a broad range of lengths and normal state resistances. We analyze the main features of the current-voltage characteristics: the Josephson current, excess current, and subgap current as functions of length, temperature, magnetic field and gate voltage, and compare them with theory. The Josephson critical current for a short length device, L = 30 nm, exhibits a record high magnitude of 800 nA at low temperature that comes close to the theoretically expected value. The critical current in all other devices is typically reduced compared to the theoretical values. The excess current is consistent with the normal resistance data and agrees well with the theory. The subgap current shows large number of structures, some of them are identified as subharmonic gap structures generated by Multiple Andreev Reflection. The other structures, detected in both suspended and non-suspended devices, have the form of voltage steps at voltages that are independent of either superconducting gap or length of the wire. By varying the gate voltage in suspended devices we are able to observe a cross over from typical tunneling transport at large negative gate voltage, with suppressed subgap current and negative excess current, to pronounced proximity junction behavior at large positive gate voltage, with enhanced Josephson current and subgap conductance as well as a large positive excess current.
Nano Letters, 2013
We report conductance and supercurrent of InAs nanowires coupled to Al-superconducting electrodes... more We report conductance and supercurrent of InAs nanowires coupled to Al-superconducting electrodes with short channel lengths and good Ohmic contacts. The nanowires are suspended 15 nm above a local gate electrode. The charge density in the nanowires can be controlled by a small change in the gate voltage. For large negative gate voltages, the number of conducting channels is reduced gradually and we observe a stepwise decrease of both conductance and critical current before the conductance vanishes completely.
Physical Review B, 2014
We present an extensive experimental and theoretical study of the proximity effect in InAs nanowi... more We present an extensive experimental and theoretical study of the proximity effect in InAs nanowires connected to superconducting electrodes. We fabricated and investigated devices with suspended gate controlled nanowires and non-suspended nanowires, with a broad range of lengths and normal state resistances. We analyze the main features of the current-voltage characteristics: the Josephson current, excess current, and subgap current as functions of length, temperature, magnetic field and gate voltage, and compare them with theory. The Josephson critical current for a short length device, L = 30 nm, exhibits a record high magnitude of 800 nA at low temperature that comes close to the theoretically expected value. The critical current in all other devices is typically reduced compared to the theoretical values. The excess current is consistent with the normal resistance data and agrees well with the theory. The subgap current shows large number of structures, some of them are identified as subharmonic gap structures generated by Multiple Andreev Reflection. The other structures, detected in both suspended and non-suspended devices, have the form of voltage steps at voltages that are independent of either superconducting gap or length of the wire. By varying the gate voltage in suspended devices we are able to observe a cross over from typical tunneling transport at large negative gate voltage, with suppressed subgap current and negative excess current, to pronounced proximity junction behavior at large positive gate voltage, with enhanced Josephson current and subgap conductance as well as a large positive excess current.
Nano Letters, 2013
We report conductance and supercurrent of InAs nanowires coupled to Al-superconducting electrodes... more We report conductance and supercurrent of InAs nanowires coupled to Al-superconducting electrodes with short channel lengths and good Ohmic contacts. The nanowires are suspended 15 nm above a local gate electrode. The charge density in the nanowires can be controlled by a small change in the gate voltage. For large negative gate voltages, the number of conducting channels is reduced gradually and we observe a stepwise decrease of both conductance and critical current before the conductance vanishes completely.