Ultracold bosons in optical lattices are an ideal system for the quantum simulation of solid-state systems [1]: they constitute a perfect periodic structure, suitable to study ordered systems, furthermore the interactions between particles are easily controlled varying the experimental parameters. Optical lattices also allow to introduce controlled inhomogeneity in the lattice sites, to study the field of disordered systems, very interesting and largely unexplored. In this framework, diagnostic techniques are still lacking to observe bosons in lattice sites with enough resolution. The work that I will present proposes an experimental investigation via noise correlation spectroscopy, applied for the first time on quasi-disordered systems [2]. Experimentally, first, we realized a Bose Einstein condensate of 87Rb and we loaded it in a 3D optical lattice, produced by pairs of counter-propagating laser beams, obtaining an insulating phase (Mott phase) with homogeneous lattice site occupation. Then we used a two-color lattice, superimposing to the first lattice a second one with different wavelength to introduce an energy offset in the lattice sites, creating a quasi-disordered potential: in this way, we break the ordered domains of the Mott insulator. We analyzed the noise correlation function of the atomic density distribution after time-of-flight in the two systems: in the first case, it shows the typical peaks in the reciprocal space depending on the lattice periodicity as in [3]. In the presence of the second lattice, which introduces the quasi-disorder, the correlation function shows instead new correlation peaks as in Fig. (1): they not correspond to the minima position of the potential but they are due to a redistribution of the atoms in the lattice sites. Therefore, we extracted information about the occupation of the atoms in the lattice sites, not available by direct observation. Through a systematic analysis, we were able to map the noise correlation as function of physical parameters of the system: this allowed making a quantitative characterization of the breaking of the ordered Mott insulating phase. References [1] D. Jaksch, C. Bruder, J. I. Cirac, C. W. Gardiner and P. Zoller, Phys. Rev. Lett. 81, 3108 (1998). [2] V. Guarrera. N. Fabbri, L. Fallani, C. Fort, Richard van der Stam, M. Inguscio, arXiv:0803.2015. [3] S. Fölling, F. Gerbier, A. Widera, O. Mandel, T. Gericke and I. Bloch, Nature 434, 481-484 (2005).
Noise correlation spectroscopy of the controlled broken order of a Mott insulating phase
Fabbri N
2008
Abstract
Ultracold bosons in optical lattices are an ideal system for the quantum simulation of solid-state systems [1]: they constitute a perfect periodic structure, suitable to study ordered systems, furthermore the interactions between particles are easily controlled varying the experimental parameters. Optical lattices also allow to introduce controlled inhomogeneity in the lattice sites, to study the field of disordered systems, very interesting and largely unexplored. In this framework, diagnostic techniques are still lacking to observe bosons in lattice sites with enough resolution. The work that I will present proposes an experimental investigation via noise correlation spectroscopy, applied for the first time on quasi-disordered systems [2]. Experimentally, first, we realized a Bose Einstein condensate of 87Rb and we loaded it in a 3D optical lattice, produced by pairs of counter-propagating laser beams, obtaining an insulating phase (Mott phase) with homogeneous lattice site occupation. Then we used a two-color lattice, superimposing to the first lattice a second one with different wavelength to introduce an energy offset in the lattice sites, creating a quasi-disordered potential: in this way, we break the ordered domains of the Mott insulator. We analyzed the noise correlation function of the atomic density distribution after time-of-flight in the two systems: in the first case, it shows the typical peaks in the reciprocal space depending on the lattice periodicity as in [3]. In the presence of the second lattice, which introduces the quasi-disorder, the correlation function shows instead new correlation peaks as in Fig. (1): they not correspond to the minima position of the potential but they are due to a redistribution of the atoms in the lattice sites. Therefore, we extracted information about the occupation of the atoms in the lattice sites, not available by direct observation. Through a systematic analysis, we were able to map the noise correlation as function of physical parameters of the system: this allowed making a quantitative characterization of the breaking of the ordered Mott insulating phase. References [1] D. Jaksch, C. Bruder, J. I. Cirac, C. W. Gardiner and P. Zoller, Phys. Rev. Lett. 81, 3108 (1998). [2] V. Guarrera. N. Fabbri, L. Fallani, C. Fort, Richard van der Stam, M. Inguscio, arXiv:0803.2015. [3] S. Fölling, F. Gerbier, A. Widera, O. Mandel, T. Gericke and I. Bloch, Nature 434, 481-484 (2005).I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
