Publications associées à Opérateur d'échelle

Numerical investigation of bound states in quantum magnets

Bound-states of particles are an interesting problem in quantum mechanics dating back to 1931 Bethe's solution of spin-1/2 Heisenberg chain. These exotic composite states are realized in quantum magnets and are detectable in inelastic neutron scattering (I ...

EPFL2023

Momentum-resolved spin-conserving two-triplon bound state and continuum in a cuprate ladder

Henrik Moodysson Rønnow, Thorsten Schmitt, Vladimir N. Strocov, Yi Tseng

Studying multi-particle elementary excitations has provided unique access to understand collective many-body phenomena in correlated electronic materials, paving the way towards constructing microscopic models. In this work, we perform O K-edge resonant in ...

NATURE PORTFOLIO2023

Semiclassical methods in conformal field theories scrutinized by the epsilon-expansion

Gil Badel

Conformal Field Theories (CFTs) are crucial for our understanding of Quantum Field Theory (QFT). Because of their powerful symmetry properties, they play the role of signposts in the space of QFTs. Any method that gives us information about their structure ...

EPFL2022

Magnetic-Field-Induced Bound States in Spin-1/2 Ladders

Frédéric Mila, Mithilesh Nayak

Motivated by the recently observed intriguing mode splittings in a magnetic field with inelastic neutron scattering in the spin ladder compound (C5H12N)(2) CuBr4 (BPCB), we investigate the nature of the spin ladder excitations using a density matrix renorm ...

2020

NMR Study of Spin Dynamics in V7Zn and V7Ni Molecular Rings

Alice Radaelli

We present a(1)H NMR investigation of spin dynamics in two finite integer spin molecular nanomagnetic rings, namely V7Zn and V7Ni. This study could be put in correlation with the problem of Haldane gap in infinite integer spin chains. While V7Zn is an appr ...

2020

Conformal 3-Point Functions and the Lorentzian OPE in Momentum Space

Marc Gillioz

In conformal field theory in Minkowski momentum space, the 3-point correlation functions of local operators are completely fixed by symmetry. Using Ward identities together with the existence of a Lorentzian operator product expansion (OPE), we show that t ...

SPRINGER2020

Harmonic analysis and mean field theory

Denis Karateev

We review some aspects of harmonic analysis for the Euclidean conformal group, including conformally-invariant pairings, the Plancherel measure, and the shadow transform. We introduce two efficient methods for computing these quantities: one based on weigh ...

Springer Nature2019

Spin dynamics of coupled spin ladders near quantum criticality in Ba2CuTeO6

Frédéric Mila

We report inelastic neutron scattering measurements of the magnetic excitations in Ba2CuTeO6, proposed by ab initio calculations to magnetically realize weakly coupled antiferromagnetic two-leg spin-1/2 ladders. Isolated ladders are expected to have a sing ...

2018

Theory and design of spherical oscillator mechanisms

Simon Nessim Henein, Roland Andreas Bitterli, Ilan Vardi, Lennart Rubbert, Mohammad Hussein Kahrobaiyan, Nicolas Ferrier, Billy Nussbaumer

In previous work, we showed that two degree of freedom oscillators can be advantageously applied to horological time bases since they can be used to eliminate the escapement mechanism. We subsequently examined planar two degree of freedom oscillators based ...

2018

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

Scale anomalies, states, and rates in conformal field theory

Marc Gillioz

This paper presents two methods to compute scale anomaly coefficients in conformal field theories (CFTs), such as the c anomaly in four dimensions, in terms of the CFT data. We first use Euclidean position space to show that the anomaly coefficient of a fo ...

Springer Nature2017

Magnetic entropy landscape and Gruneisen parameter of a quantum spin ladder

Pierre Bouillot, Daniel Biner

We present measurements of the magnetic entropy landscape and Gruneisen parameter of the Cu2+ complex (C5H12N)(2)CuCl4 in a magnetic field. Our thermodynamic measurements are in very good agreement with a theoretical description by a S = 1/2 Heisenberg lad ...

American Physical Society2014

Spin-gap evolution upon Ca doping in the spin-ladder series Sr(14−x)CaxCu24O41 studied by inelastic neutron scattering

Henrik Moodysson Rønnow, Nikolay Tsyrulin, Kazimierz Conder

The spin-gap evolution upon Ca doping in Sr14-xCaxCu24O41 was systematically investigated using inelastic neutron scattering. We discover that the singlet-triplet spin-gap excitation survives in this series with x up to 13, indicating the singlet dimer gro ...

American Physical Society2013

A New Method to Explore Conformal Field Theories in Any Dimension

Alessandro Vichi

The thesis represents an investigation into Conformal Field Theories (CFT's) in arbitrary dimensions. We propose an innovative method to extract informations about CFT's in a quantitative way. Studying the crossing symmetry of the four point function of sc ...

EPFL2011

Evidence for spinon localization in the heat transport of the spin-1/2 ladder compound (C5H12N)(2)CuBr4

Henrik Moodysson Rønnow, Christian Rüegg

We present experiments on the magnetic-field-dependent thermal transport in the spin-1/2 ladder system (C5H12N)(2)CuBr4. The thermal conductivity kappa(B) is only weakly affected by the field-induced transitions between the gapless Luttinger-liquid state r ...

2009

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

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

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

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

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

Field-Induced Staggered Magnetization and Magnetic Ordering inCu2(C5H12N2)2Cl4

Frédéric Mila

We present a 2D NMR investigation of the gapped spin-1/2 compound Cu2(C5H10N2D2)2Cl4. Our measurements reveal the presence of a magnetic field-induced transverse staggered magnetization (TSM) which persists well below and above the field-induced 3D long-ra ...

2006