| Description: | [DPS Seminar] Dr.Siddhartha Lal (IISER KolKata) -- Hall phases and a Lifshitz transition in a 2D Electron Gas with competing orders |
| Date: | Friday, Feb 20, 2015 |
| Time: | 4:30 p.m. - 6 p.m. |
| Venue: | G02, Lecture Hall Complex |
| Details: | The physics of electrons in two-dimensions continues to surprise. We investigate the competition between superconductivity and ferromagnetism in a 2D electron gas (2DEG) with strong Rashba spin-orbit coupling. Our expectation was that the anomalous Hall effect (AHE) supported by ferromagnetism should be suppressed by the presence of superconductivity. Instead, we found that dominant superconductivity supports a novel AHE of Bogolyubov-de Gennes quasiparticles. We also found that a transition from s-wave superconducting order parameter to a p_x+ip_y-type order parameter was accompanied by a change in the topology of the Fermi surface (a Lifshitz transition). This critical point is further characterised by the appearance of \pi-Berry phase carrying massless Dirac spectra in the band spectrum and an emergent spin Hall conductance. The non-monotonic variation of the superconducting order parameter with the Rashba spin-orbit interaction is likely relevant to the interface 2DEG observed at the LaO-STO heterointerface. The presence of disorder is found to lead to mesoscale phase separation phenomena. Depending on the availability of time, I will present some basics of the quantised Hall effect (QHE) and background on the connections between the anomalous and quantised Hall effect. The writeup of the work is available at arXiv:1407.6539 . |
| Calendar: | Seminar Calendar (entered by arun.ds) |