The Paired Electron Crystal: order from frustration in the quarter-filled band

Speaker: Torsten Clay, Mississippi State University

When: March 2, 2011 (Wed), 11:00AM to 12:00PM (add to my calendar)
Location: SCI 328

This event is part of the Condensed Matter Theory Seminar Series.

Abstract:
The competition between antiferromagnetic and spin-singlet ground states within quantum spin models and the 1/2-filled band Hubbard model has received intense scrutiny. In comparison, relatively little is known about the effect of lattice frustration in strongly correlated models away from 1/2 filling. Here we consider the effect of frustration in the two-dimensional interacting 1/4-filled band, and show that a frustration-induced transition from Neel antiferromagnetism to a spin-singlet state occurs. While the antiferromagnetic state has equal charge densities 0.5 on all sites, the spin-singlet state is a paired-electron crystal (PEC), with pairs of charge-rich sites separated by pairs of charge-poor sites. The PEC provides a natural description of the spin-gapped state proximate to superconductivity (SC) in many organic charge-transfer solids.