Publications de Bastien Dalla Piazza

Staggered flux state for rectangular-lattice spin-1/2 Heisenberg antiferromagnets

Henrik Moodysson Rønnow, Dmitri Ivanov, Bastien Dalla Piazza, Noore Elahi Shaik

We investigate the spin-1/2 Heisenberg model on a rectangular lattice, using the Gutzwiller projected variational wave function known as the staggered flux state. Using Monte Carlo techniques, the variational parameters and instantaneous spin-spin correlat ...

AMER PHYSICAL SOC2020

Phase diagram of diluted Ising ferromagnet LiHoxY1-xF4

Henrik Moodysson Rønnow, Peter Babkevich, Bastien Dalla Piazza, Julian Piatek, Neda Nikseresht Ghanepour, Conradin Kraemer, Ivan Kovacevic

We present a systematic study of the phase diagram of LiHoxY1-xF4 (0.25

Amer Physical Soc2016

Fractional excitations in the square-lattice quantum antiferromagnet

Henrik Moodysson Rønnow, Dmitri Ivanov, Bastien Dalla Piazza, Martin Mourigal, Goran Nilsen, Mechthild Enderle

Quantum magnets have occupied the fertile ground between many-body theory and low-temperature experiments on real materials since the early days of quantum mechanics. However, our understanding of even deceptively simple systems of interacting spin-1/2 par ...

Nature Publishing Group2015

Crystal Structure, Transport, and Magnetic Properties of an Ir6+ Compound Ba8Al2IrO14

László Forró, Henrik Moodysson Rønnow, Arnaud Magrez, Alla Arakcheeva, Lin Yang, Ana Akrap, Krunoslav Prsa, Sergiy Katrych, Bastien Dalla Piazza, Andrea Pisoni

The novel iridate Ba8Al2IrO14 was prepared as single crystals by self-flux method, thereby providing a rare example of an all-Ir(VI) compound that can be synthesized under ambient pressure conditions. The preparation of all-Ir6+ iridate without using tradi ...

2015

Magnons in tetragonal CuO

Henrik Moodysson Rønnow, Frédéric Mila, Marco Grioni, Simon Karl Moser, Thorsten Schmitt, Bastien Dalla Piazza, Sara Fatale, Noore Elahi Shaik

We investigate by resonant inelastic x-ray scattering the magnetic excitations in thin films of tetragonal CuO. We identify a spin wave excitation, dispersing on two cupratelike antiferromagnetic sublattices. Its energy at the boundary of the Brillouin zon ...

2015

Neutron spectroscopic study of crystal-field excitations and the effect of the crystal field on dipolar magnetism in LiRF4 (R = Gd, Ho, Er, Tm, and Yb)

Henrik Moodysson Rønnow, Peter Babkevich, Bastien Dalla Piazza, Conradin Kraemer, Ivan Kovacevic

We present a systematic study of the crystal-field interactions in the LiRF4 (R = Gd, Ho, Er, Tm, and Yb) family of rare-earth magnets. Using detailed inelastic neutron scattering measurements, we have been able to quantify the transition energies and wave ...

American Physical Society2015

Anisotropic softening of magnetic excitations along the nodal direction in superconducting cuprates

Henrik Moodysson Rønnow, Marco Grioni, Helmuth Berger, Thorsten Schmitt, Marco Guarise, Bastien Dalla Piazza

The high-T-c cuprate superconductors are close to antiferromagnetic order. Recent measurements of magnetic excitations have reported an intriguing similarity to the spin wavesmagnons- of the antiferromagnetic insulating parent compounds, suggesting that ma ...

Nature Publishing Group2014

Theories of Experimentally Observed Excitation Spectra of Square Lattice Antiferromagnets

Bastien Dalla Piazza

The first part of this thesis presents the theoretical study of an anomaly of unknown origin in the excitation spectrum of the Quantumspin-1/2 Heisenberg Square lattice Anti-Ferromagnet. The anomaly manifests itself in Inelastic Neutron Scattering data for ...

EPFL2014

Nonequilibrium hysteresis and spin relaxation in the mixed-anisotropy dipolar-coupled spin-glass LiHo0.5Er0.5F4

Henrik Moodysson Rønnow, Peter Babkevich, Bastien Dalla Piazza, Julian Piatek, Ivan Kovacevic, Stephen Paul Neithardt

We present a study of the model spin-glass LiHo0.5Er0.5F4 using simultaneous ac susceptibility, magnetization, and magnetocaloric effect measurements along with small angle neutron scattering ( SANS) at sub-Kelvin temperatures. All measured bulk quantities ...

American Physical Society2014

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

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

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