Törmä, Päivi
Date: Wednesday, May 13, 2015
Time: 13:30
Place: ETH Zurich, Hönggerberg, HPF G 6
Host: Tobias Donner
Quantum dynamics in ultracold Fermi gases and nanoplasmonics
Päivi Törmä
Aalto University, Finnland
We present our recent results related to two distinct topics: superfluidity in ultracold gases, and strong coupling in nanoplasmonics.
We show by theoretical arguments and dynamical mean field theory computations that in ultracold quantum gases, it is possible to realize an exotic form of superfluidity, namely the so called Fulde-Ferrel-Larkin-Ovchinnikov (FFLO) state which is characterized by a spatially varying order parameter [1]. Recently we have also found a topologically non-trivial state that simultaneously exhibits FFLO and spontaneous time-reversal symmetry breaking [2].
We predict that by imposing a different potential for the spin-up and spin-down particles leads to asymmetric critical currents in a Josephson junction between two fermionic superfluids or superconductors [3,4]. This challenges the picture of Josephson oscillations as Cooper pair tunneling and reveals that even the usual Josephson current includes a previously unidentified single particle interference contribution.
In the field of nanoplasmonics, we experimentally demonstrate strong coupling between plasmonic lattice modes and organic molecules [5,6,7], and lattice resonances enhancing magneto-optical effects [8]. We predict theoretically that Bose-Einstein condensation of photons could be possible in such a system [9].
[1] Heikkinen, M. O. J. , Kim, D.-H., Troyer, M., Törmä, P., Phys. Rev. Lett. 113, 185301 (2014).
[2] Sarjonen, R., and Törmä, P., http://arxiv.org/abs/1409.6563.
[3] Heikkinen, M. O. J., Massel, F., Kajala, J., Leskinen, M. J., Paraoanu, G. S., and Törmä, P., Phys. Rev. Lett. 105, 225301 (2010).
[4] Kreula, J.M., Heikkinen, M.O.J., Massel, F., and Törmä, P., Phys. Rev. B 89, 064502 (2014).
[5] Väkeväinen, A.I., Moerland, R.J., Rekola, H.T., Eskelinen, A.-P., Martikainen, J.-P., Kim, D.-H., and Törmä, P., Nano Lett. 14, 1721 (2014).
[6] Shi, L., Hakala, T.K., Rekola, H.T., Martikainen, J.-P., Moerland, R.J., Törmä, P., Phys. Rev. Lett. 112, 153002 (2014).
[7] Törmä, P., and Barnes, W.L., Rep. Prog. Phys. 78, 013901 (2015).
[8] Kataja, M., Hakala, T.K., Julku, A., Huttunen, M.J., van Dijken, S., and Törmä, P., Nat. Comm. in press.
[9] Martikainen J.-P., Heikkinen M. O. J., and Törmä P., Phys. Rev. A 90, 053604 (2014).