Publications by Luc Testa | EPFL Graph Search

Bullet pressure-cell design for neutron scattering experiments with horizontal magnetic fields and dilution temperatures

Henrik Moodysson Rønnow, Richard Gaal, Luc Testa, Ellen Fogh, Gaétan Charles Antoine Giriat, Jana Pásztorová

The simultaneous application of high magnetic fields and high pressures for controlling magnetic ground states is important for testing our understanding of many-body quantum theory. However, the implementation for neutron scattering experiments presents a ...

2025

Spin wave spectra of single crystal CoPS3

Henrik Moodysson Rønnow, Luc Testa, Ursula Bengaard Hansen, Mechthild Enderle

The spin waves in single crystals of the layered van der Waals antiferromagnet CoPS3 have been measured using inelastic neutron scattering. The data show four distinct spin wave branches with large (>14 meV) energy gaps at the Brillouin zone center indicat ...

2023

Spin dynamics in the square-lattice cupola system Ba(TiO)Cu-4(PO4)(4)

Henrik Moodysson Rønnow, Bruce Normand, Luc Testa, Peter Babkevich, Virgile Yves Favre

We report high-resolution single-crystal inelastic neutron scattering measurements on the spin-1/2 antiferromagnet Ba(TiO)Cu-4(PO4)(4). This material is formed from layers of four-site "cupola" structures, oriented alternately upwards and downwards, which ...

AMER PHYSICAL SOC2022

Triplons, magnons, and spinons in a single quantum spin system: SeCuO3

Henrik Moodysson Rønnow, Ivica Zivkovic, Bruce Normand, Luc Testa, Helmuth Berger

Quantum magnets display a wide variety of collective excitations, including spin waves (magnons), coherent singlet-triplet excitations (triplons), and pairs of fractional spins (spinons). These modes differ radically in nature and properties, and in all co ...

AMER PHYSICAL SOC2021

Static and dynamic properties of non-collinear quantum antiferromagnets explored by neutron scattering

Luc Testa

This thesis is devoted to the investigation of static and dynamic properties of two different sets of quantum magnets with neutron scattering techniques and the help of linear spin wave theory. Both systems are copper-based with spin-1/2, which makes them ...

EPFL2021

Magnetic Field Induced Quantum Spin Liquid in the Two Coupled Trillium Lattices of K2Ni2(SO4)(3)

Henrik Moodysson Rønnow, Arnaud Magrez, Ivica Zivkovic, Luc Testa, Peter Babkevich, Virgile Yves Favre, Nagabhushan Ganesh Hegde

Quantum spin liquids are exotic states of matter that form when strongly frustrated magnetic interactions induce a highly entangled quantum paramagnet far below the energy scale of the magnetic interactions. Three-dimensional cases are especially challengi ...

AMER PHYSICAL SOC2021

Radial Spin Texture of the Weyl Fermions in Chiral Tellurium

Majed Chergui, Henrik Moodysson Rønnow, Marco Grioni, Oleg Yazyev, Luc Testa, Daniel Gosalbez Martinez, Michele Puppin, Philippe Bugnon, Luca Moreschini, Alberto Crepaldi

Trigonal tellurium, a small-gap semiconductor with pronounced magneto-electric and magneto-optical responses, is among the simplest realizations of a chiral crystal. We have studied by spin- and angle-resolved photoelectron spectroscopy its unconventional ...

AMER PHYSICAL SOC2020

Modelling of standard and specialty fibre-based systems using finite element methods

Luc Testa

We report on the investigation of an approach for modelling light transmission through systems consisting of several jointed optical fibres, in which the analytical modelling of the waveguides was replaced by Finite Element Modelling (FEM) simulations. To ...

SPIE-INT SOC OPTICAL ENGINEERING2018

Magnetic structure of Ba(TiO)Cu4(PO4)4 probed using spherical neutron polarimetry

Henrik Moodysson Rønnow, Peter Babkevich, Luc Testa, Gregory Scott Tucker

The antiferromagnetic compound Ba(TiO)Cu4(PO4)4 contains square cupola of corner-sharing CuO4 plaquettes, which were proposed to form effective quadrupolar order. To identify the magnetic structure, we have performed spherical neutron polarimetry measureme ...

2017

Magnetic quadrupolar order in the chiral square cupola compound BaTiOCu4(PO4)4

Henrik Moodysson Rønnow, Luc Testa, Peter Babkevich, Gregory Scott Tucker

We report neutron diffraction studies of the magnetic structure in BaTiOCu4(PO4)4 , which is a newly discovered magneticinsulator crystallizing in a tetragonal chiral crystal structure with P4212 space group [1]. The crystal structure ischaracterized by an ...

2017