AtMol Research Seminar Archive
Index Current Seminars

Epiphany Term 2006

Date Speaker Home
CfAI Instrumentation, Optics and Photonics Seminar: Why not use adaptive optics to do a little good and correct the refractive error of a billion poor people?
January 12th Prof Josh Silver University of Oxford

1 pm Thursday in JKL

Experimental Realisation of Molecular Bose-Einstein Condensation
January 18th Mr Patrick Tierney Durham University

Molecular Bose-Einstein condensation (BEC) first realised in 2003 has opened a new chapter in the understanding of phenomena such as superfluidity and super conductivity. Molecular condensates are the starting point for examination of the crossover between BEC and Bardeen-Cooper-Schrieffer (BCS) superfluid behaviour. Such studies have now definitively identified superfluidity through observations of vortex lattices in a strongly interacting 6Li Fermi gas. I will begin this talk by outlining some of the difficulties associated with cooling molecules, which have resulted in the eight year gap between the creation of atomic and molecular condensates. I will then describe how colliding cold atoms may be adiabatically converted to molecular states by magnetically sweeping through a Feshbach resonance. Experimental techniques to cool and image ultra-cold molecules will be introduced, along with the different challenges experienced in cooling bosonic and fermionic Feshbach molecules. Finally I will outline some of the future directions for molecular condensates, including the use of optical lattices to create quantum degenerate bosonic molecules with relatively long lifetimes.

Molecules and Cooper Pairs in Ultracold Gases
January 25th Prof Keith Burnett University of Oxford

4:15 pm Wednesday in Ph30

I shall discuss recent progress in the study of strong correlation effects in ultracold atomic gases. This includes experiments on atoms trapped in optical lattices and taken through the superfluid-insulator phase transition, as well as the observation of BEC-BCS crossover phenomena.

A New Cs Clock Operating with nK Atoms
February 1st Dr Witold Chalupczak National Physical Laboratory

At the National Physical Laboratory a new primary frequency standards has been constructed. It is an experimental caesium fountain with the possibility of additional cooling stage in an optical lattice. After launch in the moving molasses the atoms will be cooled in the moving lattice to temperature below 200 nK. This will enable direct measurement of the collisional frequency shift in the temperature range where strong variations of the shift are expected. In my talk I am going to present the progress in the experiment.

Applied Mathematics Seminar: Dynamics of Solitons and Vortex Rings in Bose-Einstein Condensates
February 7th Dr Joachim Brand MPIPKS Dresden

1 pm Tuesday in CM221

Bose-Einstein condensates provide a newly accessible medium for the experimental study of nonlinear wave phenomena. Experimental constraints introduce new aspects in addition to the well-known soliton phenomena of the nonlinear Schroedinger equation. How much of the classical particle-like properties of solitons remain in this situation? In this talk I will discuss how bright matter-wave solitons can aquire dissipative and non-classical properties. I will also discuss the influence of transverse degrees of freedom on the collisional dynamics of dark solitons and vortex rings in cylindrical Bose-Einstein condensates. We find peculiar transient structures of spherical shape in inelastic collisions. Finally, I will discuss a recent experimental study of nonlinear-wave collisions.

Laser cooling in surface physics - towards an atom microscope
February 8th Dr Andrew Pratt University of York

Whilst laser cooling continues to provide exciting developments in the field of atomic physics, its use in the study of surface physical and chemical processes is just beginning to bear fruit. In this talk I will present an overview of our experimental set-up, in which we apply laser cooling methods to the extremely surface sensitive technique of metastable de-excitation spectroscopy. A metastable helium beam is first collimated using laser-light forces before being focussed onto a sample surface using a scanning magneto-optical lens. With further modifications based on laser cooling the instrument will be developed into a metastable-atom microscope.

CfAI Instrumentation, Optics and Photonics Seminar: Spatial Light modulators, an enabling technology in optics
February 9th Prof Miles Padgett University of Glasgow

1 pm Thursday in OC218

The Hanbury-Brown Twiss Effect in Ultracold Atomic Gases
February 22nd Ms Margaret Harris Durham University

In 1956, Robert Hanbury Brown and his collaborator Richard Q. Twiss demonstrated that identical particles which are emitted randomly by independent sources appear correlated when they are detected at a later time [1]. The signal recorded was found to increase when the detectors were close together, even though they too were entirely independent. This so-called Hanbury Brown-Twiss effect \x{2013} initally treated with great skepticism \x{2013} drew attention to the importance of two-photon amplitudes, and has been credited with establishing the field of quantum optics. HBT effects for cold atoms were first observed ten years ago [2], but within the past year the field has truly taken off, with three important experiments [3] [4] [5] showing HBT-type correlation in atomic samples at or near the BEC (BCS-BEC crossover) regime for bosons (fermions). In my talk, I will review the basic physics of HBT correlations and use this as a foundation for discussing the recent experiments and what the future may hold for HBT effects in atomic and molecular physics. References: [1] R. Hanbury Brown and R. Q. Twiss, Nature 177, 27 (1956). [2] M. Yasuda and F. Shimizu, PRL 77 3090 (1996). [3] M. Greiner et. al., PRL 94, 110401 (2005). [4] S. Fölling et. al., Nature 434 481 (2005). [5] M. Schellekens et. al., Science 310 648 (2005).

Ultracold Bosonic Gases on Atom Chips
March 1st Dr Nick Proukakis Newcastle University
Near-IR Absorption Features of Molecular Ices of Astrophysical Interest
March 8th Ms Meltem Akyilmaz Durham University

The various molecular ices have been observed on the planetary bodies, cometary nuclei and in the interstellar medium, e.g., in molecular clouds, star forming regions. The molecular ices are formed on dust grains in the interstellar medium. The dust in the interstellar medium has first taken attention of the astronomers for observational concerns. The study of dust and ice, then, became one of the most interesting and challenging research topics of molecular astrophysics. The ice mantles on the dust grains are observable through infrared wavelengths. In order to interpret the observational data, the laboratory experiments are required. In my talk, I will first review the significance of the ice and dust in molecular astrophysics, addressing the relevant questions behind the research. I will give a brief history of how dust became an area of research itself rather than an observational concern. I will summarize the observations and space based instruments that provided the data on the molecular ices present in the interstellar space and on the planetary bodies. Then I will present the recent experiments done by Gerakines et al. (2005) which provided the near-IR absorption band strengths to calculate the column densities of molecular ices of astrophysical interest. References: P.A. Gerakines, J.J. Bray, A. Davis and C.R. Richey, 2005, The Astrophysical Journal, 2005, 620:1140 P.A. Gerakines, M.H. Moore and R.L. Hudson, 2000, Astronomy and Astrophysics, 357, 793 B.T. Draine, 2003, Annual Review of Astronomy and Astrophysics, 41, 241 D.M. Hudgins, S.A. Sandford, L.J. Allamandola and A.G.G.M. Tielens, 1993, The Astrophysical Journal Supplement Series, 86:713 D.C.B. Whittet, 2003, Dust in the Galactic Environment (2nd edition; Bristol:IOP)

Decoherence: Investigating the appearance of classical physics in the quantum world
March 15th Mr Steven Wrathmall Durham University