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Bruce Normand

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Related publications (40)

Systematic extraction of crystal electric-field effects and quantum magnetic model parameters in triangular rare-earth magnets

A primary goal at the interface of theoretical and experimental quantum magnetism is the investigation of exotic spin states, mostly notably quantum spin liquids (QSLs) that realize phenomena including quasiparticle fractionalization, long-ranged entanglem ...

2021

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

A quantum magnetic analogue to the critical point of water

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

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

Multiple Magnetic Bilayers and Unconventional Criticality without Frustration in BaCuSi2O6

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

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

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

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

Thermodynamic properties of the Shastry-Sutherland model from quantum Monte Carlo simulations

Frédéric Mila, Bruce Normand

We investigate the minus-sign problem that afflicts quantum Monte Carlo (QMC) simulations of frustrated quantum spin systems, focusing on spin S = 1/2, two spatial dimensions, and the extended Shastry-Sutherland model. We show that formulating the Hamilton ...

2018

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

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

Bruce Normand, Pierre Bouillot, Daniel Biner, Christian Rüegg

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

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

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

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

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

Multi-triplet bound states and finite-temperature dynamics in highly frustrated quantum spin ladders

Frédéric Mila, Bruce Normand

Low-dimensional quantum magnets at finite temperatures present a complex interplay of quantum and thermal fluctuation effects in a restricted phase space. While some information about dynamical response functions is available from theoretical studies of th ...

2016

Thermodynamic properties of highly frustrated quantum spin ladders: Influence of many-particle bound states

Frédéric Mila, Bruce Normand

Quantum antiferromagnets have proven to be some of the cleanest realizations available for theoretical, numerical, and experimental studies of quantum fluctuation effects. At finite temperatures, however, the additional effects of thermal fluctuations in t ...

2016

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

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

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

Field-controlled magnetic order in the quantum spin-ladder system (Hpip)2CuBr4

Thierry Giamarchi, Bruce Normand, Henrik Moodysson Rønnow, Pierre Bouillot, Joël Mesot, Daniel Biner, Christian Rüegg

Neutron diffraction is used to investigate the field-induced, antiferromagnetically ordered state in the two-leg spin-ladder material (Hpip)(2)CuBr4. This "classical" phase, a consequence of weak interladder coupling, is nevertheless highly unconventional: ...

2009

Direct Observation of Magnon Fractionalization in the Quantum Spin Ladder

Bruce Normand, Henrik Moodysson Rønnow, Joël Mesot, Jean-Sebastien Caux, Daniel Biner, Christian Rüegg

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

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

Frédéric Mila, Ioannis Rousochatzakis, Bruce Normand, Salvatore Manmana

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

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

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

Bruce Normand, Henrik Moodysson Rønnow, 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

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

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