Searcharxiv⌕ Search
Home/Archive/arXiv

arXiv · cond-mat/0003223

Haldane-gap excitations in the low-H_c 1-dimensional quantum antiferromagnet NDMAP

A. Zheludev·Y. Chen·C. L. Broholm·Z. Honda·K. Katsumata
View original source ↗Read source document ↗Export metadata ↓

Abstract

Inelastic neutron scattering on deuterated single-crystal samples is used to study Haldane-gap excitations in the new S=1 one-dimensional quantum antiferromagnet NDMAP, that was recently recognized as an ideal model system for high-field studies. The Haldane gap energies $Δ_x=0.42$ meV, $Δ_y=0.52$ meV and $Δ_z=1.86$ meV, for excitations polarized along the a, b, and c crystallographic axes, respectively, are directly measured. The dispersion perpendicular to the chain axis c is studied, and extremely weak inter-chain coupling constants $J_y=1.8\cdot 10^{-3}$ meV and $J_x=3.5\cdot 10^{-4}$ meV, along the a and b axes, respectively, are determined. The results are discussed in the context of future experiments in high magnetic fields.

Explore related subjects

cond-mat.str-el

Keep this discovery

Explore connections, maps & timelines

BibTeXRIS

A. Zheludev, Y. Chen, C. L. Broholm, Z. Honda, K. Katsumata. 2000-03-13. Haldane-gap excitations in the low-H_c 1-dimensional quantum antiferromagnet NDMAP. https://doi.org/10.1103/physrevb.63.104410

Cite the original work for its findings. Save a collection to share your selection of sources.

KEEP EXPLORING

Related papers

arXiv2026

Evidence for a charged vortex lattice in an exciton superfluid

Lattices of quantized vortices are a defining property of rotating superfluids and of type-II superconductors in magnetic fields. Realizing an analogous vortex lattice in an exciton superfluid-formed from bound electron-hole pairs-has remained challenging because excitons are electrically neutral. Building on previous theoretical studies of the low-energy excitations in an exciton superfluid, recent theory has predicted that in a strong magnetic field, a weakly charged exciton superfluid can stabilize a vortex-antivortex lattice arising from the mutual repulsion of fractionally charged vortex cores. Here we report evidence for this predicted vortex lattice in a bilayer exciton condensate by imaging its charged vortices with the scanning tunnelling microscope. The condensate forms between Landau levels of two graphene layers separated by a thin hexagonal boron nitride barrier in a perpendicular magnetic field. We find that the vortex lattice periodicity scales with the total excess charge and is insensitive to its distribution between the two layers, in quantitative agreement with theoretical predictions. Our observations provide evidence for phase coherence in an exciton superfluid system.

cond-mat.str-el↗
arXiv2026

Level ordering in the linear $E \otimes e$ dynamic Jahn-Teller model

The ground level of the linear $E\otimes e$ dynamic Jahn-Teller model has long been believed to be the doublet with vibronic angular momentum $j = \pm\tfrac12$. We prove that, for arbitrary coupling strength, the $n$th level $E_{nj}$ in the subspace of fixed $j$ strictly increases with $|j|$ for every $n$, $E_{n,1/2} < E_{n,3/2} < E_{n,5/2} < \cdots$; in particular, the ground level is always the $j = \pm\tfrac12$ doublet. The proof uses only a unitary transformation that lowers $j$ by one, combined with the variational principle. We also show that the levels with fixed $j$ are nondegenerate and give explicit lower and upper bounds on the gap $E_{0,j+1} - E_{0j}$. The same Hamiltonian describes Rashba-coupled particles in harmonic traps and, in nuclear physics, the static nucleon in a charged scalar meson field.

cond-mat.str-el↗
arXiv2026

Frustration-Induced $1/6$-Vortex-Paired Phase in a Kagome XY Model

Geometric frustration can fractionalize vortices in two-dimensional XY systems, but a given frustrated model usually hosts only a single type of fractional vortex. Here we study a kagome XY model in which an antiferromagnetic coupling $J_1$ and a second-harmonic coupling $K$ favor two competing frustrated ground-state manifolds. For $K/J_1<1/9$, the ground states map onto those of the kagome three-state Potts antiferromagnet and support $1/3$ vortices; for $K/J_1>1/9$, they map onto those of the kagome Ising antiferromagnet and support $1/2$ vortices. At $K/J_1=1/9$, the two manifolds become degenerate, and bends in the domain walls between them carry $1/6$-vortex excitations. Tensor-network calculations show that a finite-temperature phase with quasi-long-range order only in $e^{6iθ}$ emerges from this degenerate point, separating the $1/3$- and $1/2$-vortex-paired phases. This $1/6$-vortex-paired phase has no counterpart in either parent manifold, showing that competing frustrated manifolds provide a route to new fractional-vortex-paired phases.

cond-mat.str-el↗