Hidden magnetic order on a kagome lattice for KV3Sb5

TL;DR

This paper proposes a model of hidden magnetic order in KV3Sb5 involving Dirac multipoles, explaining weak magnetism without long-range order, and suggests experimental tests via x-ray and neutron diffraction.

Contribution

It introduces a novel hidden magnetic order model based on Dirac multipoles, compatible with experimental observations and testable through diffraction techniques.

Findings

Proposes hidden magnetic order involving Dirac multipoles in KV3Sb5.

Predicts distinct diffraction patterns for different hidden orders.

Calculates scattering amplitudes for experimental verification.

Abstract

KV3Sb5 has recently attracted a considerable attention, due to its low temperature superconducting properties, which are heralded by a charge density wave. The apparent presence of a very weak magnetism does not result in long range ordering. We propose a model compatible with a detectable internal magnetic field with no evidence of magnetic long-range order. It invokes higher order terms in the vanadium magnetization density compatible with the presence of a "hidden order" of Dirac (polar) multipoles. The Dirac dipole, known as an anapole or toroidal dipole, is one of a family of electronic multipoles visible in x-ray and magnetic neutron diffraction while undetectable with standard laboratory-based techniques. Two plausible hidden orders are studied with a view to testing in future x-ray and neutron Bragg diffraction experiments whether they are trustworthy. One candidate is magneto-electric and restricted to the linear type, while the other candidate cannot show a magneto-electric effect of any type. The latter hosts a vanadium entity that is both a true scalar and magnetic, and its presence epitomizes an absence of loop currents. Diffraction patterns for the two proposed hidden magnetic orders are distinctly different, fortunately. Corresponding scattering amplitudes for resonant x-ray and neutron Bragg diffraction are calculated with standard chemical and magnetic symmetry tools, and atomic physics.