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Bruce Normand

Cette personne a quitté l’EPFL

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Publications associées (40)

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Magnetic order in the quasi-one-dimensional Ising system RbCoCl3

Bruce Normand, Christian Rüegg

In RbCoCl3, the magnetic Co2+ ions form weakly coupled Ising chains arranged on a triangular lattice. We have investigated the structure and magnetism in RbCoCl3 by high-resolution x-ray diffraction and neutron scattering measurements on powder and single- ...

2021

Bound States and Field-Polarized Haldane Modes in a Quantum Spin Ladder

Bruce Normand, Christian Rüegg, Pierre Bouillot, Daniel Biner

The challenge of one-dimensional systems is to understand their physics beyond the level of known elementary excitations. By high-resolution neutron spectroscopy in a quantum spin-ladder material, we probe the leading multiparticle excitation by characteri ...

Amer Physical Soc2017

Thermal Evolution of Dirac Magnons in the Honeycomb Ferromagnet CrBr3

Bruce Normand, Christian Rüegg, Andreas Martin Läuchli Herzig

CrBr3 is an excellent realization of the two-dimensional honeycomb ferromagnet, which offers a bosonic equivalent of graphene with Dirac magnons and topological character. We perform inelastic neutron scattering measurements using state-of-the-art instrume ...

2022

A quantum magnetic analogue to the critical point of water

Henrik Moodysson Rønnow, Frédéric Mila, Ludger Weber, Bruce Normand, Ellen Fogh, Christian Rüegg, Julio Antonio Larrea Jiménez

At the liquid-gas phase transition in water, the density has a discontinuity at atmospheric pressure; however, the line of these first-order transitions defined by increasing the applied pressure terminates at the critical point(1), a concept ubiquitous in ...

2021

Direct Observation of Magnon Fractionalization in the Quantum Spin Ladder

Henrik Moodysson Rønnow, Joël Mesot, Bruce Normand, Christian Rüegg, Daniel Biner

We measure by inelastic neutron scattering the spin excitation spectra as a function of applied magnetic field in the quantum spin-ladder material (C5H12N)(2)CuBr4. Discrete magnon modes at low fields in the quantum disordered phase and at high fields in t ...

2009

Thermodynamic properties of the Shastry-Sutherland model throughout the dimer-product phase

Frédéric Mila, Bruce Normand

The thermodynamic properties of the Shastry-Sutherland model have posed one of the longest-lasting conundrums in frustrated quantum magnetism. Over a wide range on both sides of the quantum phase transition (QPT) from the dimer-product state to the plaquet ...

2019

Quantum and thermal ionic motion, oxygen isotope effect, and superexchange distribution in La2CuO4

Vera Irina Schnells, Henrik Moodysson Rønnow, Sandrine Gerber, Bruce Normand, Bastien Dalla Piazza

We study the zero-point and thermal ionic motion in La2CuO4 by means of high-resolution neutron-diffraction experiments. Our results demonstrate anisotropic motion of O and, to a lesser extent, Cu ions, both consistent with the structure of coupled CuO6 oc ...

2014

Spin Waves and Three Dimensionality in the High-Pressure Antiferromagnetic Phase of SrCu2 (BO3)2

Henrik Moodysson Rønnow, Frédéric Mila, Bruce Normand, Jian Rui Soh, Ellen Fogh, Gaétan Charles Antoine Giriat

Quantum magnetic materials can provide explicit realizations of paradigm models in quantum many-body physics. In this context, SrCu2(BO3)2 is a faithful realization of the Shastry-Sutherland model for ideally frustrated spin dimers, even displaying several ...

2024

Dynamical properties of a driven dissipative dimerized S=1/2 chain

Bruce Normand

We consider the dynamical properties of a gapped quantum spin system coupled to the electric field of a laser, which drives the resonant excitation of specific phonon modes that modulate the magnetic interactions. We deduce the quantum master equations gov ...

2021

Multiple Magnetic Bilayers and Unconventional Criticality without Frustration in BaCuSi2O6

Frédéric Mila, Bruce Normand, Christian Rüegg, Gregory Scott Tucker

The dimerized quantum magnet BaCuSi2O6 was proposed as an example of "dimensional reduction" arising near the magnetic-field-induced quantum critical point (QCP) due to perfect geometrical frustration of its interbilayer interactions. We demonstrate by hig ...

2020

Efficient Quantum Monte Carlo simulations of highly frustrated magnets: the frustrated spin-1/2 ladder

Frédéric Mila, Bruce Normand

Quantum Monte Carlo simulations provide one of the more powerful and versatile numerical approaches to condensed matter systems. However, their application to frustrated quantum spin models, in all relevant temperature regimes, is hamstrung by the infamous ...

2017

Thermodynamics of the Spin Luttinger Liquid in a Model Ladder Material

Bruce Normand, Pierre Bouillot, Daniel Biner

The phase diagram in temperature and magnetic field of the metal-organic, two-leg, spin-ladder compound (C5H12N)(2)CuBr4 is studied by measurements of the specific heat and the magnetocaloric effect. We demonstrate the presence of an extended spin Luttinge ...

2008

(C5 H9NH3)2CuBr4: A metal-organic two-ladder quantum magnet

Bruce Normand

Low-dimensional quantum magnets are a versatile materials platform for studying the emergent many-body physics and collective excitations that can arise even in systems with only short-range interactions. Understanding their low-temperature structure and s ...

2024

Multiple magnon modes and consequences for the Bose-Einstein condensed phase in BaCuSi2O6

Henrik Moodysson Rønnow, Bruce Normand, Christian Rüegg

The compound BaCuSi2O6 is a quantum magnet with antiferromagnetic dimers of S=1/2 moments on a quasi-2D square lattice. We have investigated its spin dynamics by inelastic neutron scattering experiments on single crystals with an energy resolution consider ...

AMERICAN PHYSICAL SOC2007

Strong-coupling magnetophononics: Self-blocking, phonon-bitriplons, and spin-band engineering

Bruce Normand

Magnetophononics, the modulation of magnetic interactions by driving infrared-active lattice excitations, is emerging as a key mechanism for the ultrafast dynamical control of both semiclassical and quantum spin systems by coherent light. We demonstrate th ...

2023

Electronic and magnetic excitations in the half-stuffed Cu-O planes of Ba2Cu3O4Cl2 measured by resonant inelastic x-ray scattering

Henrik Moodysson Rønnow, Marco Grioni, Thorsten Schmitt, Bruce Normand, Peter Babkevich, Sara Fatale, Noore Elahi Shaik, Claudia Giuseppina Fatuzzo

We use resonant inelastic x-ray scattering (RIXS) at the Cu L3 edge to measure the charge and spin excitations in the “half-stuffed” Cu-O planes of the cuprate antiferromagnet Ba2Cu3O4Cl2. The RIXS line shape reveals distinct contributions to the dd excita ...

2017

Static impurities in the S=3/2 kagome lattice: Exact diagonalization calculations on small clusters

Frédéric Mila, Bruce Normand

We consider the effects of doping the S=3/2 kagome lattice with static, nonmagnetic impurities. By exact-diagonalization calculations on small clusters, we deduce the local spin correlations and magnetization distribution around a vacancy. As in the S=1/2 ...

2007

Dzyaloshinskii-Moriya anisotropy and nonmagnetic impurities in the s=1/2 kagome system ZnCu3(OH)(6)Cl-2

Frédéric Mila, Bruce Normand

Motivated by recent nuclear magnetic resonance experiments on ZnCu3(OH)(6)Cl-2, we present an exact-diagonalization study of the combined effects of nonmagnetic impurities and Dzyaloshinskii-Moriya (DM) interactions in the s = 1/2 kagome antiferromagnet. T ...

2009

Thermal Critical Points and Quantum Critical End Point in the Frustrated Bilayer Heisenberg Antiferromagnet

Frédéric Mila, Bruce Normand

We consider the finite-temperature phase diagram of the S = 1/2 frustrated Heisenberg bilayer. Although this two-dimensional system may show magnetic order only at zero temperature, we demonstrate the presence of a line of finite-temperature critical point ...

2018

Thermal Control of Spin Excitations in the Coupled Ising-Chain Material RbCoCl3

Bruce Normand, Christian Rüegg

We have used neutron spectroscopy to investigate the spin dynamics of the quantum (S = 1/2) antiferromagnetic Ising chains in RbCoCl3. The structure and magnetic interactions in this material conspire to produce two magnetic phase transitions at low temper ...

2020