INVITADO: Leticia Tarruell 
ICFO1The Institute of Photonic Sciences, Barcelona (Spain)

Date:26 de septiembre, 2013 
Time:14:30 
Place:3rd floor seminar lecture room. Dpt. Física Teórica I. Facultad de Ciencias Físicas UCM.


ABSTRACT 

Ultracold"atomic"gases"in"optical"lattices"provide"the"opportunity"of" engineering"synthetic"quantum"materials"in"a"clean"and"highly"controlled" environment."On"the"one"hand,"these"systems"can"be"viewed"as" experimental"quantum"simulators"for"exploring"challenging"problems"of" condensed"matter"physics."On"the"other"hand,"they"also"allow"for"the" realization"of"completely"novel"materials"of"interesting"properties,"without" counterpart"in"solid1state"systems. In"my"talk,"I"will"present"recent"experiments"where"an"ultracold"Fermi"gas" trapped"in"an"optical"lattice"of"tunable"geometry"is"used"to"explore"both" aspects. By"loading"non1interacting"atoms"into"a"honeycomb"structure,"we"realize" artificial"graphene"and"observe"the"presence"of"two"Dirac"points"in"the" band"structure"[1]."The"flexibility"of"our"experimental"approach"allows"us" to"adjust"the"properties"of"these"Dirac"points"at"will,"moving"them"inside" the"Brillouin"zone"and"changing"the"effective"mass"of"the"associated"Dirac" fermions."Furthermore,"we"observe"how"the"two"Dirac"points"annihilate" each"other"when"coming"too"close"together,"a"situation"which"is"presently" out"of"reach"in"solid1state"samples. Preparing"instead"a"repulsively"interacting"gas"of"atoms"in"two"different" internal"states,"we"implement"the"Fermi1Hubbard"model"and"aim"at" simulating"quantum"magnetism"in"this"system."In"particular,"we"explore" experimentally"how"certain"crystal"geometries"favor"the"emergence"of" short1range"magnetic"order,"and"directly"probe"the"nearest1neighbor"spin" correlations"of"the"system"[2]."In"a"dimerized"lattice,"the"correlations" manifest"as"an"excess"number"of"singlets"as"compared"to"triplets,"whereas" in"an"anisotropic"simple"cubic"lattice"we"observe"the"appearance"of" antiferromagnetic"correlations"along"one"spatial"axis."