Scattering of particles or light is an experimental technique widely used to get information on the structure of condensed-matter systems. Inelastic scattering, in which the energy of the probe beam changes after the scattering event, is particularly important since it allows to obtain precious information on the dynamics of excitations, which characterize the nature of the system under investigation. We have applied these ideas to investigate systems of ultracold bosonic atoms trapped in optical lattices. Two laser beams with different frequencies and directions are used to induce stimulated inelastic scattering of light from the atomic sample. In this two-photon process, also known as Bragg scattering [1,2,3] the internal state of the atoms is unchanged and the excitations only involve the external degrees of freedom. The energy and momentum transfer can be easily controlled by changing respectively the frequency and the direction of the excitation beams. We have used this technique to investigate the low-energy excitation spectrum of interacting 1D Bose gases across the crossover from a superfluid to a Mott insulating state [4]. Significant modifications in the excitation spectrum are observed when the system is driven into the insulating phase. In particular, the non-zero momentum transfer used in the experiment allows exciting the Mott state in a linear regime previously unaccessed by experiments. We have also recently studied excitations towards higher-energy bands (i.e. towards single-particle states), which give direct information on the one-body spectral function in the Mott state. We will present the results of these studies and discuss the perspectives connected to the investigation of different many-body systems such as 1D Bose gases entering the strongly correlated regime of Tonks-Girardeau. [1] Kozuma M et al. (1999) Phys. Rev. Lett. 82, 871. [2] Stenger J et al. (1999) Phys. Rev. Lett. 82, 4569. [3] Ozeri R et al. (2005) Rev. Mod. Phys. 77, 187. [4] Cl_ement D, Fabbri N, Fallani L, Fort C and Inguscio M. (2009) Phys. Rev. Lett. 102, 155301.
Exploring correlated phases of ultracold bosons in optical lattices by inelastic light scattering
Fabbri N;
2009
Abstract
Scattering of particles or light is an experimental technique widely used to get information on the structure of condensed-matter systems. Inelastic scattering, in which the energy of the probe beam changes after the scattering event, is particularly important since it allows to obtain precious information on the dynamics of excitations, which characterize the nature of the system under investigation. We have applied these ideas to investigate systems of ultracold bosonic atoms trapped in optical lattices. Two laser beams with different frequencies and directions are used to induce stimulated inelastic scattering of light from the atomic sample. In this two-photon process, also known as Bragg scattering [1,2,3] the internal state of the atoms is unchanged and the excitations only involve the external degrees of freedom. The energy and momentum transfer can be easily controlled by changing respectively the frequency and the direction of the excitation beams. We have used this technique to investigate the low-energy excitation spectrum of interacting 1D Bose gases across the crossover from a superfluid to a Mott insulating state [4]. Significant modifications in the excitation spectrum are observed when the system is driven into the insulating phase. In particular, the non-zero momentum transfer used in the experiment allows exciting the Mott state in a linear regime previously unaccessed by experiments. We have also recently studied excitations towards higher-energy bands (i.e. towards single-particle states), which give direct information on the one-body spectral function in the Mott state. We will present the results of these studies and discuss the perspectives connected to the investigation of different many-body systems such as 1D Bose gases entering the strongly correlated regime of Tonks-Girardeau. [1] Kozuma M et al. (1999) Phys. Rev. Lett. 82, 871. [2] Stenger J et al. (1999) Phys. Rev. Lett. 82, 4569. [3] Ozeri R et al. (2005) Rev. Mod. Phys. 77, 187. [4] Cl_ement D, Fabbri N, Fallani L, Fort C and Inguscio M. (2009) Phys. Rev. Lett. 102, 155301.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
