Seminários

Seminário de matéria condensada

When&where: Nov. 10th, 2016, 11:00, room 528 (Torre Nova)

Speaker: David Möckli (IF-UFF)

Title: The pair-density wave phase of multilayer superconductors

 

Abstract:

 

In this seminar I will present the results obtained during my visiting PhD year at ETH Zürich. 

 

Recently, a state-of-the-art molecular beam epitaxy technique was developed to reduce the dimensionality of heavy electron systems by fabricating artificial superlattices that include heavy fermion compounds. This allows for engineering of new 2D electronic states. Motivated by these experiments, we theoretically investigate a superconducting artificial trilayer system, where singlet Cooper pairs are depaired mainly through spin polarization due to an external magnetic field perpendicular to the layers. In such a system, the outer layers locally lack inversion symmetry. This is manifested by a Rashba effect at the outer layers, reducing Cooper depairing in these layers. This together with interlayer coupling, stabilizes an exotic layer dependent odd singlet superconducting state, which is called a pair-density wave (PDW) phase. This phase is a superconducting parity-mixed state and is robust against an external magnetic field. The PDW phase is achieved through a first order phase transition and is a topological crystalline state protected by a mirror symmetry. However, experiments are expected to display vortex physics. For this reason, we investigate the single vortex problem in the PDW phase by means of a phenomenological Ginzburg-Landau theory. We find an intriguing parity-mixed vortex with a layer dependent phase twisting. If the PDW phase survives a vortex lattice of such vortices is still an open question to be answered very soon.