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Dresden 2006 – scientific programme

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TT: Tiefe Temperaturen

TT 28: Correlated Electrons: General Theory

TT 28.11: Talk

Thursday, March 30, 2006, 12:45–13:00, HSZ 301

Exotic excitations with fractional charges on frustrated lattices — •Frank Pollmann1, Peter Fulde1, and Erich Runge21Max-Planck-Institut für Physik komplexer Systeme, Nöthnitzer Str. 38, 01187 Dresden, Germany — 2Technische Universität Ilmenau, Weimarer Str. 25, 98693 Ilmenau, Germany

Geometrical frustration of lattices can lead to a macroscopic degeneracy in the classical limit and thus to many interesting physical effects. In spin systems these are e.g. translational invariant spin liquid ground states and deconfined spinons. In contrast to magnetic properties, one began only recently to explore the charge degrees of freedom on frustrated lattices.
For the systematic study of charge degrees of freedom, we consider a model of spinless fermions with nearest-neighbor hopping t and Coulomb repulsion V. Quantum fluctuations reduce the classical (t=0) macroscopic degeneracy. For the strongly correlated limit V≫|t|, it has been predicted that an added electron can decay into two mobile quasi-particles, leading to fractional charges of e/2 in 2D and 3D systems.
For a deeper understanding of these charge degrees of freedom we calculated numerically the properties of static and dynamic charges on the 2D checkerboard lattice. Evidence for a weak mutual confinement of two fractional charges is found, leading to excitations with very large spatial extend. We argue that the fractional charges should be deconfined on the 3D pyrochlore lattice.

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