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Emergent BCS regime and pseudogap in the 2D Hubbard model

Evgeny Kozik, King's College London, UK

21.07.2017 at 09:00 

 

A significant part of the phase diagram of the 2D fermionic Hubbard model in the non- perturbative regime of moderate interactions and filling factors (U<4,n<0.7) is governed by effective Fermi liquid physics with emergent weak BCS-type instabilities.
I will discuss how the bold-line diagrammatic Monte Carlo technique with semi-analytic treatment of the Cooper instability can be used to address this system without uncontrolled approximations.
I will present an accurate ground-state phase diagram in the (n,U) plane, describing competition between the p- and  d-wave superfluid states. However, critical temperatures prove to be small in this regime at least up to U=4, n=0.6,  where skeleton expansions for the Hubbard model break down and the bare series diverges.
I will introduce a method for controlling the convergence radius of bare diagrammatic expansions, which allows us to investigate in a controllable manner the pseudogap regime of the Hubbard model and to study the nodal/antinodal dichotomy at low doping and values of coupling inaccessible before.

A 450, Theresienstr. 37