Nanopatterning of Weak Links in Superconducting Oxide Interfaces.

Gyanendra Singh,Alexei Kalaboukhov,Edouard Lesne,Thilo Bauch,Andrea D Caviglia,Floriana Lombardi,Dag Winkler,Tord Claeson

doi:10.3390/nano11020398

Gyanendra Singh, Alexei Kalaboukhov + Show 6 more

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https://doi.org/10.3390/nano11020398

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Abstract

The interface between two wide band-gap insulators, LaAlO and SrTiO (LAO/STO), hosts a quasi-two-dimensional electron gas (q2DEG), two-dimensional superconductivity, ferromagnetism, and giant Rashba spin-orbit coupling. The co-existence of two-dimensional superconductivity with gate-tunable spin-orbit coupling and multiband occupation is of particular interest for the realization of unconventional superconducting pairing. To investigate the symmetry of the superconducting order parameter, phase sensitive measurements of the Josephson effect are required. We describe an approach for the fabrication of artificial superconducting weak links at the LAO/STO interface using direct high-resolution electron beam lithography and low-energy argon ion beam irradiation. The method does not require lift-off steps or sacrificial layers. Therefore, resolution is only limited by the electron beam lithography and pattern transfer. We have realized superconducting weak links with a barrier thickness of 30–100 nm. The barrier transparency of the weak links can be controlled by the irradiation dose and further tuned by a gate voltage. Our results open up new possibilities for the realization of quantum devices in oxide interfaces.

Highlights

Complex oxide interfaces have recently been recognized as a powerful platform to engineer and study novel electronic phases [1]
The latter is an important feature for device patterning in the LaAlO3 and SrTiO3 (LAO/STO) interface as presence of surface contamination may significantly alter the carrier concentration and electron mobility of the electron gas [36,37]
We found that the actual irradiation time that is required to achieve an insulating state varies from sample to sample

Summary

Introduction

Complex oxide interfaces have recently been recognized as a powerful platform to engineer and study novel electronic phases [1]. That exhibits superconductivity, co-existing with intrinsic ferromagnetism and large gatetunable spin-orbit coupling, in the interface between two wide band-gap insulators, LaAlO3 and SrTiO3 (LAO and STO), has stimulated increasing interest in both experimental and theoretical studies of this system [6,7,8,9,10,11,12,13,14]. The combination of two-dimensional superconductivity with multiband occupation and strong Rashba spin-orbit coupling in the LAO/STO interface is very promising in a realization of superconducting pairing with unconventional order parameter [15,16,17,18].

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