pdf, 9 MiB - Infoscience - EPFL
pdf, 9 MiB - Infoscience - EPFL
pdf, 9 MiB - Infoscience - EPFL
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Computer skills<br />
• Computer languages: FORTRAN 77, FORTRAN 95, and some knowledge of C++.<br />
• Parallel programming: Good knowledge of MPI. Extensive experience in performing<br />
calculations on parallel machines (mizar.epfl.ch, pleiades.epfl.ch).<br />
• Techniques: Lanczos diagonalizations, Monte-Carlo for classical spin systems,<br />
Variational Quantum Monte-Carlo, Green-Function Monte-Carlo, Auxiliary-field<br />
Quantum Monte-Carlo, Monte-Carlo algorithms for polymers.<br />
Research interests<br />
My current research interests are mainly concerned with strongly-correlated electron systems<br />
and frustrated spin models. In parallel, I was also interested by scanning tunneling<br />
microscopy experiments. The tools used include both numerical (exact diagonalization,<br />
classical and quantum Monte Carlo) and analytical (mean-field, slave boson approximations)<br />
techniques. My scientific activity has focused on the following fields (reference numbers relate<br />
to the List of publications hereafter):<br />
1. Physics of frustrated classical spin models<br />
o<br />
o<br />
o<br />
Phase transition driven by Frustration. In connection with the physical<br />
properties of Li 2 VOSiO 4 , we have carried on extensive classical Monte Carlo<br />
simulations for the anti-ferromagnetic Heisenberg model with both nearest (J 1 )<br />
and next-nearest (J 2 ) exchange couplings on the square lattice. The long-range<br />
magnetic order is known to be destroyed by thermal or quantum fluctuations at<br />
finite temperature (Mermin-Wagner theorem). However, it was found that<br />
frustration can induce a non-trivial phase transition related at a finite<br />
temperature related to a discrete symmetry breaking [1].<br />
Coupling to the lattice. It is also relevant, when comparing with experiments,<br />
to study the coupling of the spin degrees of freedom to the lattice. Indeed, the<br />
Ising-like phase transition, that appears for J 2 /J 1 >1/2 in the pure spin model, was<br />
found to be still present and even strengthened by the spin-lattice coupling, and<br />
is accompanied by a lattice deformation from a tetragonal symmetry to an<br />
orthorhombic one. Evidences that the universality class of the transition does<br />
not change with the inclusion of the spin-lattice coupling was reported.<br />
Implications for the prototype for a layered J 1 -J 2 model in the collinear region<br />
were discussed [5].<br />
Effect of static disorder. Presently we are studying the effect of static disorder<br />
in a frustrated spin model, and presently we found that non trivial interaction<br />
between disorder and frustration occurs.