Dresden 2017 – wissenschaftliches Programm

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TT: Fachverband Tiefe Temperaturen

TT 20: Poster Session: Correlated Electrons 2

TT 20.13: Poster

Montag, 20. März 2017, 15:00–19:00, P2-OG1

Exact Diagonalization study of large Hubbard clusters — •Michael Danilov¹, Sergei Iskakov², Malte Harland¹, and Alexander Lichtenstein¹ — ¹I. Institut für Theoretische Physik Jungiusstrasse 9, 20355 Hamburg, Germany — ²Department of Physics, University of Michigan, Ann Arbor, Michigan 48109, USA

Using efficient exact diagonalization scheme, we studied electronic structure of 4x4 doped Hubbard cluster with realistic hopping parameters including next nearest neighbour hopping t′ = -0.3t, which is optimal for superconducting cuprates. The Green’s function and abnormally large density of states near Fermi level are analysed as function of doping and strength of local Coulomb interactions.

In order to compare the spectrum of the 16-site cluster against small 2x2 plaquette, where the ground state is 6-fold degenerate for special values of Coulomb interactions and chemical potential (Phys. Rev. B 94 (2016) 125133), we scale the hopping between the 4 plaquettes constituting the cluster with auxiliary parameter α.

We examined the degeneracy of low-energy spectra as function of α and local Coulomb interaction U and visualised the ground state wavefunction. Our current standpoint is that the optimal Coulomb interaction is close to U=10t, versus U=6t for degenerate ground state of isolated plaquette. We discuss the relevance of degenerate low-energy spectra with regard to possible mechanism of the high-temperature superconductivity.