Aspen Wednesday

Morning:
*Randy Hulet talked about recent data on very strongly interacting Li-7 BEC (near Feshbach resonance) --- extremely interesting: as the BEC approaches resonance (stronger interaction), the chemical potential (measured from size of condensate) deviates from the value expected for BEC (even with beyond mean field Lee-Yang-Huang correction) and seems approaching the fermi energy as if the strongly interacting bosons starting to behave like fermions!
More data is needed to confirm this remarkable preliminary observation but much discussions followed in the workshop.
Some of such physics has been predicted in the paper by Fei Zhou:
http://arxiv.org/PS_cache/arxiv/pdf/0902/0902.0366v2.pdf
[Note added: Since the 3-body recombination loss is quite large when approaching the resonance, I think it might have something to do with the recent work on "loss/dissipation induced (dynamically generated) effective correlation/interaction", as discussed in Zoller et al: PRL 102, 040402 (2009) in relation to an experiment by Rempe et al: N. Syassen et al., Science 320, 1329 (2008) , in addition, Zoller has another visionary paper on strongly driven quantum systems :Nature Physics 4, 878-883 (2008) --- there could be a new paradigm of generating novel quantum phases "dynamically".
* Robin Cote gave a tutorial on AMO physics. I attended the part 2-3 on atoms and molecules.
interesting stuff mentioned:
- Peter Zoller's talk in NSF QIS workshop 2009: http://www.eas.caltech.edu/qis2009/program.html (many good talks)
- Rempe's work on using pulsed laser as repump? -- I can't find it though
- sympathetic coolding b/t molecules and alkali atoms (Heather Lewandowski)
- 2008 PRA's by E. Kuznetsova et al on polar molecule phase gates ("Analysis of experimental feasibility of polar-molecule-based phase gates") and STIRAP (Formation of deeply bound molecules via chainwise adiabatic passage)

During coffee break, had some extremely interesting discussions with Gordon Semenoff on graphene:
1) chiral symmetry breaking (Nambu mechanism) should be possible in graphene if can control Coulomb interaction (relative to hopping say) ---- in other words this corresponds to Mott transition as U/t increases, GS says electrons in graphene are not far from such transition, can probe say
1a) reducing t by stretching
1b) chemically modifying t (hopping) both very interesting experiments!
[Note--- the threshold U/t (~5, in real graphene value ~4) for fermions in honeycomb lattice not known -- Klauss Ziegler said he may be able to calculate, will follow up!]
2) chiral/sublattice polarization may occur in low B, and detectable with "sublattice valve"? (bilayer region etc. )
3) renormalization of speed of light and dependence on size --- later discussed with Dan Sheehy

Afternoon:
Had an interesting discussion with Dan Sheehy (LSU) --- 1) The "effective speed of light" (ie fermi velocity) in graphene in fact suppose to have higher order QED corrections, eg. proportional to ln(L/a), L sample size and a lattice constant, the velocity should approach c in vacuum for infinite sample. So finite-size (up to very large sample) dependent study may reveal such evolution --- good to measure v_F for a series of samples of different sizes! Finite freq, magnetic field variation and large density variation may also help. Check on various measurements of v_F in literature, eg. transport, optics, STM, Yacoby (n-dependent), and heat capacity? (not yet) -- they do not all agree! 2) BEC-BCS crossover of fermions on honeycomb lattice --- suppose to have no BCS SF because no fermi surface in honeycomb --? 3) discussed possible BCS BEC crossover in quantum Hall bilayer, if so, where is the cross over point in d/a (1.8?) --- need a bound state to appear? May check 2D bound state of a free hole to electron(s) from another layer?