arXiv subjects

Matthias Lopez

Publications and source records attributed to Matthias Lopez.

3 recordsLinked to original sources

arXiv2016

Competition between Spin Echo and Spin Self-Rephasing in a Trapped Atom Interferometer

We perform Ramsey interferometry on an ultracold 87Rb ensemble confined in an optical dipoletrap. We use a π-pulse set at the middle of the interferometer to restore the coherence of the spinensemble by canceling out phase inhomogeneities and creating a spin echo in the contrast. However,for high atomic densities, we observe the opposite behavior: the π-pulse accelerates the dephasingof the spin ensemble leading to a faster contrast decay of the interferometer. We understand thisphenomenon as a competition between the spin-echo technique and an exchange-interaction drivenspin self-rephasing mechanism based on the identical spin rotation effect. Our experimental data iswell reproduced by a numerical model.

physics.atom-ph↗

arXiv2013

Phase diagram of the Anderson transition with atomic matter waves

We realize experimentally a cold atom system equivalent to the 3D Anderson model of disordered solids where the anisotropy can be controlled by adjusting an experimentally accessible parameter. This allows us to study experimentally the disorder vs anisotropy phase diagram of the Anderson metal-insulator transition. Numerical and experimental data compare very well with each other and a theoretical analysis based on the self-consistent theory of localization correctly discribes the observed behavior, illustrating the flexibility of cold atom experiments for the study of transport phenomena in complex quantum systems.

cond-mat.dis-nn↗

arXiv2011

Experimental Test of Universality of the Anderson Transition

We experimentally test the universality of the Anderson three dimensional metal-insulator transition. Nine sets of parameters controlling the microscopic details of this second order phase transition have been tested. The corresponding critical exponents are independent (within $2σ$) of these microscopic details, and the average value $1.63\pm0.05$ is in very good agreement with the numerically predicted value, $ν= 1.58$.

quant-ph↗