CPM Seminar

Simultaneous Charge Ordering and Spin Dimerization:
Theory of the spin-SAF Transition

Gennady Y. Chitov

Department of Physics
Laurentian University

We propose the theory of the phase transition in a spin-pseudospin model comprised of the frustrated quantum Ising model coupled to the Heisenberg spin chains. The (spin-SAF) transition occurs into a phase with co-existent super-antiferromagnetic (SAF) pseudospin long-range order and a spin gap. The theory is applied to the quarter-filled ladder compound NaV₂O₅ , where pseudospins represent its charge degrees of freedom. Broader implications of the spin-SAF transition as an example of a new order emerging from spin-charge correlations, resulting in, e.g., destruction of a quantum critical point will be emphasized. Several universal properties unifying the spin-SAF and spin-Peierls transitions will be discussed.