Dionys Baeriswyl - Université de Fribourg (CH) #	
25 years of high-temperature superconductivity: Lessons from variational 
calculations #
Interacting electrons on a square lattice, as 
described for instance by the Hubbard Hamiltonian, represent 
undoubtedly the central issue in the quest for a microscopic 
understanding of cuprate superconductors. This talk will present 
variational results for the 2D Hubbard model [1], which exhibit 
a superconducting ground state for a certain doping range, in 
surprisingly good agreement with experiments. Our ansatz belongs 
to a class of trial states which are "adiabatically" linked to a 
simple reference state and therefore not ideally suited for 
describing quantum phase transitions [2]. Possible ways out of 
this dilemma are briefly discussed.
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[1] D. Baeriswyl, D. Eichenberger and M. Menteshashvili, New J. 
Phys. 11, 075010 (2009).<br/>
[2] D. Baeriswyl, to appear in Ann. Phys. (Berlin) 19 (2011).