Past colloquia and seminars


Dynamic change at the superconducting transition in gate-controlled AlOx/SrTiO3 heterostructure

Academic or specialist Seminar

Doped SrTiO3 crystals exhibit a superconducting dome1 with a maximum critical temperature around 300 mK. SrTiO3 is supposed to be a ferroelectric at low temperatures. However, quantum zero point fluctuations ensure that it remains a paraelectric2. At 105 K, it undergoes a ferroelastic transition3 from cubic to tetragonal symmetry. The domains become polar below 40 K. There are many interesting questions regarding the role of the structural properties of SrTiO3 on the emergence of the superconducting state. A pertinent development in recent years is the realization of superconducting two-dimensional electron gases (2DEGs) in SrTiO3-based heterostructures. The carrier density of such 2DEGs is tunable with an electrostatic gate voltage, leading to the observation of a superconducting dome4. We have conducted experiments on the superconducting transition in the AlOx/SrTiO3 interface electronic system5. The onset of the phase transition was probed with gate-voltage-tuning of carrier density, which in turn leads to the growth of superconducting islands. Following a change of gate voltage, a slow dynamic change of tens of seconds was observed in the resistivity close to the phase transition. This timescale is significantly larger in the superconducting state compared to the normal state. The observed timescale is consistent with the characteristic relaxation times6 of ferroic domains in SrTiO3 under an applied electric field. Our observations7 indicate that ferroic domains facilitate the nucleation and growth of superconducting islands. It reveals the strong impact of structural properties of the substrate on the superconducting state of the interface electronic system.

When? 13.10.2022 14:00
Where? PER 08 2.73
Chemin du Musée 3
1700 Fribourg
speaker Shamashis Sengupta
IJCLab, CNRS/IN2P3, Université Paris-Saclay
Contact Département de physique, Magnetism and Superconductivity Group
Prof. Christian Bernhard