Talk given by Dr. Srijit Goswami Kavli Institute of Nanoscience Delft University of Technology Delft, The Netherlands Abstract: For many decades now, two-dimensional electron systems (2DESs) have served as a platform to explore various aspects of mesoscopic physics. In 2004, it was shown that a new class of 2DES could be engineered at the interface between transition metal oxides which are band insulators. The interface between Strontium Titanate (STO) and Lanthanum Aluminate (LAO) is one such oxide interface which has been heavily studied. Among many other fascinating properties, this LAO/STO interface hosts a 2D superconductor [1], where the critical temperature can be controlled via the field effect [2]. Here, I will discuss our efforts to study this superconductor at mesoscopic length scales. In particular we use local top gates [3], which exploit the field effect to enable in-situ creation and control of the Josephson junctions (JJs). While other examples of gate-tunable JJs do exist, they necessarily involve physical interfaces between two dissimilar materials. In contrast, our gate-defined JJs are unique in that the entire device is made from a single superconductor with purely electrostatic interfaces between the superconducting reservoir and the weak link. We use two such independently controllable JJs to create a superconducting quantum interference device (SQUID), which demonstrates for the first time the ability to perform measurements which are sensitive to the phase of superconducting order parameter of this unique 2D superconductor. Finally, I will discuss how the extremely low superfluid density of this superconductor has striking effects on the operation of the SQUID. [1] Superconducting interfaces between insulating oxides, N. Reyren et al., Science316, 1196 (2007) [2] Electric field control of the LaAlO_3 /SrTiO_3 interface ground state, A. D. Caviglia et al., Nature 456, 624 (2008) [3] Nanoscale electrostatic control of oxide interfaces, S. Goswami et al., Nano Letters 15, 2627 (2015)

This event is part of the eventgroup INT Talks

Homepage
https://www.int.kit.edu/events.php

Speaker
Dr. Srijit Goswami

Delft University of Technology, Delft, The Netherlands
http://qt.tudelft.nl/people/

Organizer
Dr. Romain Danneau
Institute of Nanotechnology (INT)
Karlsruhe Institute of Technology (KIT)
Eggenstein-Leopoldshafen
Tel: 0721/608-28896
Mail: romain danneau ∂does-not-exist.kit edu

Targetgroup
Interested / Everyone