Avinash Singh
Articles written in Pramana – Journal of Physics
Volume 29 Issue 5 November 1987 pp 509-516 Condensed Matter Physics
Hubbard model: revisited—a macroscopic renormalization group study
The spin-correlation length is used to set up a RG analysis of the Hubbard model (within RPA). We demonstrate that an identical critical behaviour is obtained by performing the macroscopic renormalization group analysis with the antisymmetric Landau interaction parameter. The beta functions for the half-filled and quarter-filled band cases have been evaluated.
Volume 44 Issue 1 January 1995 pp 1- Rapid Communication
Gap states in a doped Mott-Hubbard insulator
Prasenjit Sen Saurabh Basu Avinash Singh
Static, non-magnetic impurities give rise to gap states in a doped Mott-Hubbard antiferromagnetic insulator. The spectral and spatial features of these gap states are discussed, and it is argued that these gap states are responsible for the observed local-moment behaviour in zinc-doped cuprates.
Volume 49 Issue 5 November 1997 pp 505-514
Self-consistent numerical study of pure and impurity doped three-band Hubbard model
The three-band Hubbard model — both pure and with static non-magnetic impurities — has been studied within a self-consistent numerical Hartree-Fock (HF) scheme. The system shows nesting properties only in the absence of direct O-O hopping. Spin excitations in the system are gapless with the existence of a Goldstone mode in the broken-symmetry state. The variation of spinwave velocity with Cu-site Coulomb repulsion shows a (1/(2
Volume 70 Issue 1 January 2008 pp 163-171 Research Articles
Anisotropic Hubbard model on a triangular lattice - spin dynamics in HoMnO3
The recent neutron scattering data for spin-wave dispersion in HoMnO3 are well-described by an anisotropic Hubbard model on a triangular lattice with a planar (XY) spin anisotropy. Best fit indicates that magnetic excitations in HoMnO3 correspond to the strong-coupling limit $U/t > \sim 15$, with planar exchange energy $J = 4t^{2}/U \simeq 2.5$ meV and planar anisotropy $\Delta U \simeq 0.35 $meV.
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