CM seminars coming up

[Cond.Matt. & Stat.Mech.Section]

SEMINAR on  Disorder and strong electron correlations





Thursday, 11 February      -  11:00 a.m.



EULER LECTURE HALL,  Leonardo Building - terrace level



Andrea TROMBETTONI    ( S.I.S.S.A. )



"Strongly correlated states in low dimensional Bose gases"



Abstract



Ultracold atoms can be trapped in strongly confined low dimensional  
trap geometries like (1D) cigars and (2D) pancakes: this allows for to  
experimentally simulate Hamiltonians having strongly correlated ground  
states.  The 1D Bose gas is well described by the so called Lieb- 
Liniger Hamiltonian: in the talk I will discuss a recently proposed  
method to compute expectation values and other physical quantities.   
The method is based on the observation that the S-matrix and the  
Lagrangian of the Lieb-Liniger model can be obtained as a non- 
relativistic limit of an integrable relativistic field theory, the  
sinh-Gordon model.  In the final part of the talk, I will briefly  
discuss the effect of an experimentally realizable artificial non- 
abelian magnetic field acting on a 2D ultracold atomic gas, showing  
that it is possible to tune the Hamiltonian parameters in order to  
have non-abelian excitations.



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JOINT ICTP/SISSA CONDENSED MATTER SEMINAR



Euler Lecture Hall - ICTP Leonardo Building  (terrace level)





Wednesday, 17 February -     4:00 p.m.



  Dirk VAN DER MAREL    ( Universite de Geneve )



"What makes superconductivity happen  at high temperature?"



Abstract



Superconductivity and magnetism are often considered as antagonistic  
phenomena.  Indeed the phenomenon of superconductivity is usually  
observed in materials showing no instabilities toward magnetic order  
of any kind.  However, in recent decades several new classes of  
superconductors have been discovered where superconductivity occurs on  
the brink of magnetic order, and in a limited number of examples  
coexistence of superconductivity and ferromagnetism has even been  
claimed.  In many of these new materials the Cooper-pairs were  
observed and/or predicted to have finite angular momentum, and  
sometimes even finite spin.  The field of superconductivity has, so to  
speak, become very 'rich' and ever so more fascinating.  In this  
Colloquium I will, based on the state of affairs in unconventional  
superconductivity, argue in favour of the scenario where high  
temperature superconductivity arises from pairing mediated through the  
virtual exchange of spin fluctuations.  This is born out by a vast  
body of experimental data obtained worldwide using photo-electron  
spectroscopy, tunnelling and optics.  These experiments have enabled  
the community to establish the temperature and energy dependence of  
the dissipation and the mass renormalization of the charge carriers in  
various materials including the high Tc superconductors.  Based on the  
energy range observed for the inelastic scattering, it is now possible  
to eliminate phonon mediated pairing as 'the' mechanism of  
superconductivity in the cuprates, and provide quantitative arguments  
in favour of the thesis that superconductivity in these materials is  
driven by proximity to magnetic (or stripe) instability.