arXiv subjects

U. Hizi

Publications and source records attributed to U. Hizi.

3 recordsLinked to original sources

arXiv2005

Effective Hamiltonian for the Pyrochlore antiferromagnet: semiclassical derivation and degeneracy

In the classical pyrochlore lattice Heisenberg antiferromagnet, there is a macroscopic continuous ground state degeneracy. We study semiclassical limit of large spin length $S$, keeping only the lowest order (in 1/S) correction to the classical Hamiltonian. We perform a detailed analysis of the spin-wave modes, and using a real-space loop expansion, we produce an effective Hamiltonian, in which the degrees of freedom are Ising variables representing fluxes through loops in the lattice. We find a family of degenerate collinear ground states, related by gauge-like $Z_2$ transformations and provide bounds for the order of the degeneracy. We further show that the theory can readily be applied to determine the ground states of the Heisenberg Hamiltonian on related lattices, and to field-induced collinear magnetization plateau states.

cond-mat.str-el↗

arXiv2005

Semiclassical ordering in the large-N pyrochlore antiferromagnet

We study the semiclassical limit of the $Sp(N)$ generalization of the pyrochlore lattice Heisenberg antiferromagnet by expanding about the $N \to \infty$ saddlepoint in powers of a generalized inverse spin. To leading order, we write down an effective Hamiltonian as a series in loops on the lattice. Using this as a formula for calculating the energy of any classical ground state, we perform Monte-Carlo simulations and find a unique collinear ground state. This state is not a ground state of linear spin-wave theory, and can therefore not be a physical (N=1) semiclassical ground state.

cond-mat.str-el↗

arXiv2003

Hole on a stripe in a spinless fermion model

In the spinless fermion model on a square lattice with infinite nearest-neighbor repulsion, holes doped into the half-filled ordered state form stripes which, at low doping, are stable against phase separation into an ordered state and a hole-rich metal. Here we consider transport of additional holes along these stripes. The motion of a single hole on a stripe is mapped to a one-dimensional problem, a variational wavefunction is constructed and the energy spectrum is calculated and compared to energies obtained by exact diagonalization.

cond-mat.str-el↗