Dynamical properties of quantum antiferromagnets in one and two dimensions

Kyungmin Lee, Ronald Melendrez, Arijeet Pal +1 more

Nonequilibrium properties of quantum materials present many intriguing properties, among them athermal behavior, which violates the eigenstate thermalization hypothesis. Such behavior has primarily been observed in disordered systems. More recently, experimental and theoretical evidence for athermal eigenstates, known as ``quantum scars,'' has emerged in nonintegrable disorder-free models in one dimension with constrained dynamics. In this Rapid Communication, we show the existence of quantum scar eigenstates and investigate their dynamical properties in many simple two-body Hamiltonians with ``staggered'' interactions, involving ferromagnetic and antiferromagnetic motifs, in arbitrary dimensions. These magnetic models include simple modifications of widely studied ones (e.g., the XXZ model) on a variety of frustrated and unfrustrated lattices. We demonstrate our ideas by focusing on the two-dimensional frustrated spin-1/2 kagome antiferromagnet, which was previously shown to harbor a special exactly solvable point with ``three-coloring'' ground states in its phase diagram. For appropriately chosen initial product states---for example, those which correspond to any state of valid three-colors---we show the presence of robust quantum revivals, which survive the addition of anisotropic terms. We also suggest avenues for future experiments which may see this effect in real materials.

Subir Sachdev A

Subir Sachdev A, Kwon Park

Junwu Gan, D. H. Lee, Per Hedegård

We investigate the effect of hole doping on the strong-coupling Hubbard model at half filling in spatial dimensions D\ensuremath{\ge}1. We start with an antiferromagnetic mean-field description of the insulating state, and show that doping creates solitons in the antiferromagnetic background. In one dimension, the soliton is topological, spinless, and decoupled from the background antiferromagnetic fluctuations at low energies. In two dimensions and above, the soliton is nontopological, has spin quantum number 1/2, and is strongly coupled to the antiferromagnetic fluctuations. We derive the effective action governing the quasiparticle motion, study the properties of a single carrier, and comment on a possible description at finite concentration. \textcopyright{} 1996 The American Physical Society.

Grégoire Misguich, C. Lhuillier

Piotr Tomczak, A. Ryszard Ferchmin, Johannes Richter

The ground-state properties of the antiferromagnetic, nearest-neighbor, frustrated Heisenberg spin-1/2 system on a nontranslational lattice of dimension d=ln3/ln2 are investigated. The argument is presented indicating that quantum fluctuations, frustration, lack of translational symmetry, and reduction of dimension of the system from d=2, but kept above d=1, taken together lead to a disordered ground state in quantum antiferromagnets. \textcopyright{} 1996 The American Physical Society.