Single-pole ladder at quarter filling

D. N. Aristov, M. N. Kiselev, K. Kikoin

Research output: Contribution to journalArticlepeer-review

6 Scopus citations

Abstract

We study the ground state and excitation spectrum of a quasi-one- dimensional system consisting of a pole and rungs oriented in opposite directions ("centipede ladder," CL) at quarter filling. The spin and charge excitation spectra are found in the limits of small and large longitudinal hoppings t compared to the on-rung hopping rate t and exchange coupling I. At small t, the system with ferromagnetic on-rung exchange demonstrates instability against dimerization. Coherent propagation of charge-transfer excitons is possible in this limit. At large t, CL behaves like two-orbital Hubbard chain, but the gap opens in the charge excitation spectrum, thus reducing the symmetry from SU(4) to SU(2). The spin excitations are always gapless and their dispersion changes from quadratic magnonlike for ferromagnetic on-rung exchange to linear spinonlike for antiferromagnetic on-rung exchange in weak longitudinal hopping limit.

Original languageEnglish
Article number224405
JournalPhysical Review B - Condensed Matter and Materials Physics
Volume75
Issue number22
DOIs
StatePublished - 7 Jun 2007
Externally publishedYes

ASJC Scopus subject areas

  • Electronic, Optical and Magnetic Materials
  • Condensed Matter Physics

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