Internships and PhDs

Master Internship : Mesoscopic devices at oxide interfaces (2020-2021)

Electric-field effect control of two-dimensional electron gases has enabled the exploration of nanoscale electron quantum transport in semiconductors. Beyond these materials, transition metal-oxide-based structures have d-electronic states favoring the emergence of novel quantum orders absent in conventional semiconductors. In this context, the 2D electron gas formed at the LaAlO3/SrTiO3 interface, which combines gate-tunable superconductivity and strong spin-orbit coupling is a promising platform to develop novel electronic devices1 (Fig1). This unique combination of properties can promote topological superconductivity, an exotic electronic state with remarkable chiral properties. In particular, topological superconductors are predicted to be suitable hosts for Majorana zero energy modes, which could be used to encode and manipulate non-local quantum information, opening new perspectives for the realization of "fault tolerant" quantum computation technology2.
The objective of this project is to fabricate and study mesoscopic nanodevices in which superconductivity and spin-orbit coupling could be tuned at the relevant scales using a set of nano-gates. We have recently demonstrated the realization of a Quantum Point Contact devices formed by electrostatic confinement of the LaAlO3/SrTiO3 interface in the lateral direction (Fig 1d), and investigated the normal state quantized conductance3. The first objective of this thesis is to supplement our dc transport measurements by quantum shot noise measurements and achieve spin control in the QPC. The second and main objective is to investigate topological superconductivity in devices involving superconducting parts coupled by a 1D normal region of strong Rashba spin-orbit coupling.

Figure 1: a) TEM picture of a LaAlO3/SrTiO3 interface. b) Superconducting transition. Phase diagram of a the interface. d) Quantum Point Contact made in a LaAlO3/SrTiO3 interface.

1 Caviglia, A. D. et al. Electric field control of the LaAlO 3 /SrTiO 3 interface ground state. Nature 56, 624–627 (2008).
2 A. Stern and N. H. Lindner, Topological quantum computation—from basic concepts to first experiments. Science 339, 1179–1184 (2013).
3 A. Jouan et al. Quantized conductance in a one-dimensional ballistic oxide nanodevice.. Nature Elec. 3, 201–206 (2020).

Experimental tools : very low temperature cryogenic, microfabrication in clean room, dc and microwave transport measurements (10 mK)

Prerequisite : Student with a strong background in physics and motivated by experimental science.

Funding : The 3 years PhD thesis will be funded by the ANR contract QUANTOP.

Contact : Nicolas Bergeal
nicolas.bergeal (arobase)