Since the discovery of a two-dimensional electron gas (2DEG) at the interface between two band insulating oxide, SrTiO3 (STO), a wealth of intriguing properties have emerged in this seemingly simple system. They exhibit superconductivity, incipient magnetism, thermoelectricity and electronic correlations. The properties of the interfaces can be tuned dramatically in numerous ways such as by controlling oxygen vacancies, electrostatic gate potentials and strain [1]. Thus, 2DEG at complex oxide interfaces as STO has an enormous potential with scientific and technological impacts in oxide nanoelectronic devices.
Raman spectroscopy is a powerfull optical technique to study the ferroelectricity (soft phonon mode), electronic and magnetic (magnon) excitations under various external fields. In addition, application of strain or pressure can induce novel electronic states in strongly correlated systems. We have then developped an experimental setup to achieve both compressive and tensile uniaxial strain and another one to apply hydrostatic pressure in single crystal or thin films to discover new electronic phenomena. Our work has given already important contributions in the field [1-3].
The goal of this internship is to study the properties of STO and Ca-doped STO under uniaxial strain using Raman spectroscopy. The trainee will be accompanied on the whole experiment from the bonding of the samples on the uniaxial stress system, to the use of cryostat to reach 3K, to the application of the stress and to the optical measurements with Raman spectroscopy. The candidate should have an appetite for experimental research. It will then be possible to work on a microscopic model to understand these measurements in collaboration with theorists.
This work is based on collaboration with UMR φ Thales and is a premilary step for a thesis.
[1] Non-collinear and strongly asymmetric polar moments at back-gated SrTiO3 interfaces, F. Lyzwa, et al. NPJ Comm. Phys. 5, 133 (2022).
[2] Switchable two-dimensional electron gas based on ferroelectric Ca:SrTiO3, J. Bréhin, et al. Rapid. Comm. Phys. Rev. Mat. 4, 041002(R) (2020). [Editor’s recommendation + Featured in Physics]
[3] Colossal electromagnon excitation in the non-cycloidal phase of TbMnO3 under pressure, I. Aupiais et al, NPJ Quantum Materials 3, 60 (2018).