Creation and Destruction of a Spin Gap in Weakly Coupled Quarter-Filled Ladders

Abstract

We investigate weakly coupled quarter-filled ladders with model parameters relevant for NaV(2)O(5) using density-matrix renormalization group calculations on an extended Hubbard model coupled to the lattice. NaV(2)O(5) exhibits super-antiferroelectric charge order with a zigzag pattern on each ladder. We show that this order causes a spin dimerization along the ladder and is accompanied by a spin gap of the same magnitude as that observed experimentally. The spin gap is destroyed again at large charge order due to a restructuring of the spins. An analysis of an effective spin model predicts a recreation of the gap by interladder singlets when the charge order increases further.

Ground State and Finite Temperature Behavior of 1/4-Filled Band Zigzag Ladders

“…Below the transition the V-ions are charge disproportionated and there occurs a period-4 V 4+ -V 4+ -V 5+ -V 5+ CO within the zigzag links between the rectangular ladders. Once again, the strongest bonds are between the spin 1 2 electron-rich V 4+ ion pairs and the weakest bonds between the spin 0 electron-poor V 5+ ion pairs, 68,69 in agreement with our criterion for coupled CO-SG transition.…”

Effective Hamiltonian for the electronic properties of the quasi-one-dimensional material Li0.9Mo6O17Merino1, McKenzie2 2012Phys. Rev. B252490View full textAdd to dashboardCite

“…From DFT-based calculations the parameters are estimated to be t 0.17 eV, t ⊥ 3t, and U 2.8 eV. The distance between vanadium ions along the chain is approximately 3.8Å and the nearest-neighbor Coulomb repulsion V has been estimated 57 to be V ≈ 2t consistent with the zig-zag type charge ordering 58 found in these systems.…”

Unconventional superconducting phases for the two-dimensional extended Hubbard model on a square lattice

“…[6][7][8][9][10][11] Meanwhile, in a two-leg ladder, a checkerboard charge-ordered state has been proposed for all fillings between quarter and half, with on-site and nearest-neighbor repulsion. 12 Its application to the coupled quarter-filled ladders with coupling to the lattice has recently been studied 13 to explain the spin gaps in the NaV 2 O 5 material. 14,15 On a two-dimensional lattice, the extended Hubbard model has been considered a paradigmatic model to search for possible unconventional superconducting phases since the discovery of high-temperature superconductivity in the cuprates.…”

“…Meanwhile, in a two-leg ladder, a checkerboard charge-ordered state has been proposed for all fillings between quarter and half, with on-site and nearest-neighbor repulsion 12 . Its application to the coupled quarter-filled ladders with coupling to the lattice has recently been studied 13 to explain the spin gaps in the NaV 2 O 5 material 14,15 .…”