pdf, 9 MiB - Infoscience - EPFL

Computer skills
• Computer languages: FORTRAN 77, FORTRAN 95, and some knowledge of C++.
• Parallel programming: Good knowledge of MPI. Extensive experience in performing
calculations on parallel machines (mizar.epfl.ch, pleiades.epfl.ch).
• Techniques: Lanczos diagonalizations, Monte-Carlo for classical spin systems,
Variational Quantum Monte-Carlo, Green-Function Monte-Carlo, Auxiliary-field
Quantum Monte-Carlo, Monte-Carlo algorithms for polymers.
Research interests
My current research interests are mainly concerned with strongly-correlated electron systems
and frustrated spin models. In parallel, I was also interested by scanning tunneling
microscopy experiments. The tools used include both numerical (exact diagonalization,
classical and quantum Monte Carlo) and analytical (mean-field, slave boson approximations)
techniques. My scientific activity has focused on the following fields (reference numbers relate
to the List of publications hereafter):
1. Physics of frustrated classical spin models
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Phase transition driven by Frustration. In connection with the physical
properties of Li 2 VOSiO 4 , we have carried on extensive classical Monte Carlo
simulations for the anti-ferromagnetic Heisenberg model with both nearest (J 1 )
and next-nearest (J 2 ) exchange couplings on the square lattice. The long-range
magnetic order is known to be destroyed by thermal or quantum fluctuations at
finite temperature (Mermin-Wagner theorem). However, it was found that
frustration can induce a non-trivial phase transition related at a finite
temperature related to a discrete symmetry breaking [1].
Coupling to the lattice. It is also relevant, when comparing with experiments,
to study the coupling of the spin degrees of freedom to the lattice. Indeed, the
Ising-like phase transition, that appears for J 2 /J 1 >1/2 in the pure spin model, was
found to be still present and even strengthened by the spin-lattice coupling, and
is accompanied by a lattice deformation from a tetragonal symmetry to an
orthorhombic one. Evidences that the universality class of the transition does
not change with the inclusion of the spin-lattice coupling was reported.
Implications for the prototype for a layered J 1 -J 2 model in the collinear region
were discussed [5].
Effect of static disorder. Presently we are studying the effect of static disorder
in a frustrated spin model, and presently we found that non trivial interaction
between disorder and frustration occurs.