Regensburg 2010 – scientific programme

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TT: Fachverband Tiefe Temperaturen

TT 30: CE: Low-dimensional Systems - Models 1

TT 30.2: Talk

Thursday, March 25, 2010, 09:45–10:00, H20

Orbital currents and SU(2) spin rotational symmetry breaking in doped two-leg Cu-O Hubbard ladders. — •Piotr Chudzinski¹, Marc Gabay², and Thierry Giamarchi¹ — ¹DPMC-MaNEP, University of Geneva, Geneva, Switzerland — ²LPS, Université Paris-Sud 11, Orsay Cedex, France

In the weak-coupling limit, we study, as a function of doping, two leg ladders with a unit cell containing both Cu and O atoms. For purely repulsive interactions, using bosonization and a novel RG scheme, we find that in a broad region of the phase diagram, the ground state consists of a pattern of orbital currents (OCP) defined on the top of an incommensurate density wave. We focus on this OCP and check what kind of changes in the phase diagram one may expect due to SU(2) spin-rotational symmetry breaking. We also investigate a single impurity problem (incl. OCP): we discuss the nature of impurity backscattering, check if Kondo physics is at play. This enables us to show the influence of SU(2) symmetry breaking on conductivity. We estimate the value of gap opened due to the OCP and discuss magnetic properties of a new phase. Finally we investigate the influence, on the phase diagram, of other possible SU(2) breaking mechanisms. The motivation comes from the fact that two-leg ladder Hamiltonian can be used to describe broader class of materials of interest for example zig-zag carbon nanotubes.