Magnetic vortex lattice in HgBa2CuO4+x observed by small-angle neutron scattering

TL;DR

This study directly observes the magnetic vortex lattice in HgBa2CuO4+x using small-angle neutron scattering, revealing a triangular vortex structure at low fields and a transition to 2D behavior at higher fields.

Contribution

It provides the first direct observation of the vortex lattice in HgBa2CuO4+x, demonstrating its triangular structure and field-dependent dimensional crossover.

Findings

Triangular vortex lattice observed at low magnetic fields.

Vortex signal diminishes and vanishes above 0.4 Tesla.

Transition from 3D to 2D vortex system with increasing magnetic field.

Abstract

We report a direct observation of the magnetic vortex lattice in the model high-temperature superconductor HgBa2CuO4+x. Using small-angle neutron scattering on high-quality crystals, we observe two equal domains of undistorted triangular vortex lattices well-aligned with the tetragonal crystallographic axes. The signal decreases rapidly with increasing magnetic field and vanishes above 0.4 Tesla, which we attribute to a crossover from a three-dimensional to a two-dimensional vortex system, similar to previous results for the more anisotropic compound Bi2.15Sr1.95CaCu2O8+x. Our result indicates that a triangular vortex lattice at low magnetic fields is a generic property to cuprates with critical temperatures above 80 K.