Date:
Thu, 26/10/201712:00-13:30
Location:
Danciger B building, Seminar room
Lecturer: Prof. Marco Aprili, Laboratoire de Physique des Solides, Université Paris-Sud
Abstract:
The excitations in conventional superconductors, Bogoliubov quasiparticles, are spin-1/2 fermions but their charge and group velocity is energy-dependent and, in fact, zero at the gap edge. Therefore, in superconductors (unlike normal metals) the spin and charge degrees of freedom may be spatially separated. I will first present a series of experiments that address spin imbalance [1], magnetization relaxation [2] and spin coherence [3] of the out-of-equilibrium magnetization induced in a mesoscopic superconducting device by spin injection. Then I will focus on a very recent experiment on spectroscopy [4] of this state. I will show that the spins distribution is energy dependent as expected once the quasiparticle velocity taken into account. I will describe such a distribution of charge-less spin polarized quasiparticles using a diffusion equation and I will show that the gap changes follow the self-consistent gap equation. Finally I will address the quasiparticle lifetime and interaction in the situations where either one or both spin species (up and down) are injected.
[1] C.H.L Quay et al. Nature Physics 9, 84-88 (2013)
[2] C.H.L Quay et al. PRB 93, 220501 (R) (2016)
[3] C.H.L Quay et al. Nature Communications 6, 8660 (2015)
[4] M. Kuzmanovic et al. in preparation.
Abstract:
The excitations in conventional superconductors, Bogoliubov quasiparticles, are spin-1/2 fermions but their charge and group velocity is energy-dependent and, in fact, zero at the gap edge. Therefore, in superconductors (unlike normal metals) the spin and charge degrees of freedom may be spatially separated. I will first present a series of experiments that address spin imbalance [1], magnetization relaxation [2] and spin coherence [3] of the out-of-equilibrium magnetization induced in a mesoscopic superconducting device by spin injection. Then I will focus on a very recent experiment on spectroscopy [4] of this state. I will show that the spins distribution is energy dependent as expected once the quasiparticle velocity taken into account. I will describe such a distribution of charge-less spin polarized quasiparticles using a diffusion equation and I will show that the gap changes follow the self-consistent gap equation. Finally I will address the quasiparticle lifetime and interaction in the situations where either one or both spin species (up and down) are injected.
[1] C.H.L Quay et al. Nature Physics 9, 84-88 (2013)
[2] C.H.L Quay et al. PRB 93, 220501 (R) (2016)
[3] C.H.L Quay et al. Nature Communications 6, 8660 (2015)
[4] M. Kuzmanovic et al. in preparation.