Publications de François Vernay

Antiferromagnetic Spin-S Chains with Exactly Dimerized Ground States

Frédéric Mila, Frédéric Alexis Michaud, François Vernay, Salvatore Manmana

We show that spin S Heisenberg spin chains with an additional three-body interaction of the form (Si-1 center dot S-i)(S-i center dot S-i (+) (1)) + H.c. possess fully dimerized ground states if the ratio of the three-body interaction to the bilinear one i ...

2012

Theory of inelastic light scattering in spin-1 systems: Resonant regimes and detection of quadrupolar order

Frédéric Mila, Frédéric Alexis Michaud, François Vernay

Motivated by the lack of an obvious spectroscopic probe to investigate nonconventional order such as quadrupolar orders in spin S > 1/2 systems, we present a theoretical approach to inelastic light scattering for spin-1 quantum magnets in the context of a ...

2011

Charge disproportionation in RNiO3 perovskites (R=rare earth) from high-resolution x-ray absorption spectroscopy

Marco Grioni, François Vernay, Joël Mesot

High-resolution x-ray absorption measurements reveal a rare-earth-dependent splitting of the Ni K edge in the insulating, charge-disproportionated state of the whole RNiO3 perovskite family. The splitting is five times larger for LuNiO3 [2.5(1) eV] than fo ...

2009

Identification of an RVB liquid phase in a quantum dimer model with competing kinetic terms

Frédéric Mila, François Vernay

Starting from the mean-field solution of a spin-orbital model of LiNiO2, we derive an effective quantum dimer model (QDM) that lives on the triangular lattice and contains kinetic terms acting on four-site plaquettes and six-site loops. Using exact diagona ...

2006

Orbital degeneracy as a source of frustration inLiNiO2

Frédéric Mila, François Vernay, Karlo Penc

2005

Dégénérescence orbitale et ordre magnétique sur le réseau triangulaire : le cas des composés LiNiO2 et NaNiO2

François Vernay

Compounds made of transition metal ions on a triangular lattice may have orbitally degenerate eg states. This is the case for LiNiO2 and NaNiO2 : the Ni3+ ions are in a low-spin state, leaving the last electron of the d-shell in the eg orbitals. In order t ...

EPFL2005