Simultaneous Charge Ordering and Spin Dimerization in Quasi-Two-Dimensional Quarter-Filled Ladders

Abstract

We study the spin-pseudospin Hamiltonian of the Ising Model in Transverse Field (IMTF) for pseudospins, coupled to the XY-spins on a triangular lattice. This model appears from analyses of the quarter-filled ladder compound $Na{V}_2{O}_5$, and pseudospins represent its charge degrees of freedom. In the molecular-field approximation we find that the model possesses two phases: charge-disordered without spin gap; and a low-temperature phase containing both the anti-ferroelectric (zigzag) charge order and spin dimerization (spin gap). The phase transition is of the second kind, and the calculated physical quantities are as those one expects from the Landau theory. One of particular features of the phase diagram is that the inter-ladder spin-pseudospin coupling, responsible for the spin gap generation, also destroys the IMTF quantum critical point, resulting in the exponential behavior of $T_c$ in the region of Ising's coupling where the IMTF is always disordered. We conclude that our mean-field results give a qualitatively correct description of the phase transition in $Na{V}_2{O}_5$, while a more sophisticated analysis is warranted in order to take into account the thermal fluctuations and, probably, the proximity of the IMTF quantum critical point.

arXiv comment17 pages, 2 figures

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Cited by in corpus (7)

• Quantum Criticality in Dimerized Spin Ladders
• Ordering in Two-Dimensional Ising Models with Competing Interactions
• Phase diagram and topological order in the modulated $XYZ$ chain with magnetic fields
• Creation and destruction of a spin gap in weakly coupled quarter-filled ladders
• Topological floating phase in a spatially anisotropic frustrated Ising model
• On the Stacking Charge Order in NaV2O5
• The Spin-SAF transition in NaV2O5 induced by spin-pseudospin coupling