Publications de Bruce Normand | EPFL Graph Search

Fingerprints of supersymmetric spin and charge dynamics observed by inelastic neutron scattering

Andreas Martin Läuchli Herzig, Bruce Normand

Supersymmetry is an algebraic property of a quantum Hamiltonian that, by giving every boson a fermionic superpartner and vice versa, may underpin physics beyond the Standard Model. Fractional bosonic and fermionic quasiparticles are familiar in condensed m ...

NATURE PORTFOLIO2025

Confined and Deconfined Spinon Excitations in the Rectangular-lattice Quantum Antiferromagnet

Bruce Normand, Henrik Moodysson Rønnow, Noore Elahi Shaik, Ellen Fogh

Fractionalization remains one of the most fascinating manifestations of strong interactions in quantum many-body systems. In quantum magnetism, the existence of spinons-collective magnetic excitations that behave as quasiparticles with fractional quantum n ...

AMER PHYSICAL SOC2025

(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

Field-induced bound-state condensation and spin-nematic phase in SrCu2(BO3)2 revealed by neutron scattering up to 25.9 T

Frédéric Mila, Bruce Normand, Henrik Moodysson Rønnow, Alexandra Angeline Turrini, Mithilesh Nayak, Ellen Fogh, Jian Rui Soh

In quantum magnetic materials, ordered phases induced by an applied magnetic field can be described as the Bose-Einstein condensation (BEC) of magnon excitations. In the strongly frustrated system SrCu2(BO3)(2), no clear magnon BEC could be observed, point ...

Nature Portfolio2024

Molecular intercalation in the van der Waals antiferromagnets FePS3 and NiPS3

Bruce Normand, Xiaoyu Xu, Sheng Xu, Ying Chen, Zeyu Wang, Shuo Li, Weiqiang Yu

We have performed electrochemical treatment of the van der Waals antiferromagnetic materials FePS3 and NiPS3 with the ionic liquid EMIM-BF4, achieving significant molecular intercalation. Mass analysis of the intercalated compounds, EMIMx-FePS3 and EMIMx-N ...

Amer Physical Soc2024

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

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

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

Multinode quantum spin liquids in extended Kitaev honeycomb models

Bruce Normand

Variational Monte Carlo (VMC) studies of extended Kitaev honeycomb models reveal a series of multinode quantum spin liquids (QSLs). They have an emergent Z2 gauge structure, a discrete number of symmetry-protected Majorana cones, and form Abelian or non-Ab ...

NATURE PORTFOLIO2024

Field-controlled multicritical behavior and emergent universality in fully frustrated quantum magnets

Bruce Normand

Phase transitions in condensed matter are a source of exotic emergent properties. We study the fully frustrated bilayer Heisenberg antiferromagnet to demonstrate that an applied magnetic field creates a previously unknown emergent criticality. The quantum ...

Nature Portfolio2024

Superconductivity in nickelate and cuprate superconductors with strong bilayer coupling

Bruce Normand

The discovery of superconductivity at 80 K under high pressure in La3Ni2O7 3 Ni 2 O 7 presents the groundbreaking confirmation that high-Tc T c superconductivity is a property of strongly correlated materials beyond cuprates. We use density functional theo ...

AMER PHYSICAL SOC2024

Ultrafast frustration breaking and magnetophononic driving of singlet excitations in a quantum magnet

Bruce Normand, Nicola Colonna, Christian Rüegg

Ideal magnetic frustration forms the basis for the emergence of exotic quantum spin states that are entirely nonmagnetic. Such singlet spin states are the defining feature of the Shastry-Sutherland model, and of its faithful materials realization in the qu ...

2023

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

Complete field-induced spectral response of the spin-1/2 triangular-lattice antiferromagnet CsYbSe2

Andreas Martin Läuchli Herzig, Bruce Normand

Fifty years after Anderson's resonating valence-bond proposal, the spin-1/2 triangular-lattice Heisenberg antiferromagnet (TLHAF) remains the ultimate platform to explore highly entangled quantum spin states in proximity to magnetic order. Yb-based delafos ...

Nature Portfolio2023

Investigating field-induced magnetic order in Han purple by neutron scattering up to 25.9 T

Philippe Heller, Frédéric Mila, Bruce Normand, Nicolas Laflorencie

BaCuSi2O6 is a quasi-two-dimensional (2D) quantum antiferromagnet containing three different types of stacked, square-lattice bilayer hosting spin-1/2 dimers. Although this compound has been studied extensively over the last two decades, the critical appli ...

2022

Thermal Evolution of Dirac Magnons in the Honeycomb Ferromagnet CrBr3

Andreas Martin Läuchli Herzig, Bruce Normand, Christian Rüegg

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

Randomness and frustration in a S = (1/)(2) square-lattice Heisenberg antiferromagnet

Bruce Normand, Henrik Moodysson Rønnow, Peter Babkevich, Ellen Fogh

We explore the interplay between randomness and magnetic frustration in the series of S = 12 Heisenberg square-lattice compounds Sr2CuTe1???xWxO6. Substituting W for Te alters the magnetic interactions dramatically, from strongly nearest-neighbor to next-n ...

2022

Quantum Monte Carlo simulations in the trimer basis: First-order transitions and thermal critical points in frustrated trilayer magnets

Frédéric Mila, Bruce Normand

The phase diagrams of highly frustrated quantum spin systems can exhibit first-order quantum phase transitions and thermal critical points even in the absence of any long-ranged magnetic order. However, all unbiased numerical techniques for investigating f ...

SCIPOST FOUNDATION2022

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

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

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

Revealing three-dimensional quantum criticality by Sr substitution in Han purple

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

Classical and quantum phase transitions (QPTs), with their accompanying concepts of criticality and universality, are a cornerstone of statistical thermodynamics. An excellent example of a controlled QPT is the field-induced ordering of a gapped quantum ma ...

2021

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

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

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

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