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Dynamics of self-organization of atoms in cavities

Event Details

Event Dates: 

Wednesday, March 11, 2015 - 12:00pm

Seminar Location: 

  • JILA X317

Speaker Name(s): 

Stefan Schütz

Speaker Affiliation(s): 

Saarland University
Seminar Type/Subject

Scientific Seminar Type: 

  • JILA Public Seminar

Event Details & Abstract: 

Laser-cooled atoms in optical resonators can self-organize in spatially-ordered structures. Self organization sets in when the strength of the cooling laser, which directly pumps the atoms, exceeds a threshold value. Then, the ordered structures are stable and support coherent scattering of the atoms into the resonator, so that the  cavity optical potential is maximized [1]. In turn, the cavity field  mediates infinitely long-range interactions between the atoms, giving  rise to novel dynamics. The dynamics of the onset of self organization  in this system is characterized by several peculiar features, which  emerge because of the long-range interparticle potential. In this  contribution we present an analytical and numerical study of the  dynamics of self organization, which is based on a Fokker-Planck  equation we derived assuming that the atomic motion is in the  semiclassical regime [2]. We show that at steady state the sample is  in a thermal distribution, whose temperature does not depend on the  pump strength but is only limited by the cavity line width. On the  other hand, above threshold the steady state exhibits density-density correlations, to which one can associate a behaviour analogous to magnetization. Using numerical simulations we show that the dynamics  leading to the stationary state is characterized by two time

scales: after a violent relaxation, the system slowly reaches the stationary states over time scales which exceed the cavity lifetime by several orders of magnitude [3]. We analyze in details the corresponding field at the cavity output as a tool to monitor this behaviour. Finally, we draw analogies with the Hamiltonian-Mean-Field  model [4] and argue that this system can be used as a testbed for  studying the predictions of the statistical mechanics of long-range  interacting systems.

 

References

[1] H. Ritsch, P. Domokos, F. Brennecke, and T. Esslinger, Rev. Mod.

Phys. 85, 553 (2013)

[2] S. Schütz, H. Habibian, and G. Morigi, Phys. Rev. A 88, 033427 (2013) [3] S. Schütz, and G. Morigi, Phys. Rev. Lett. 113, 203002 (2014) [4] A. Campa, T. Dauxois, and S. Ruffo, Physics Reports 480, 57-159 (2009)