Ultracold gases in optical lattices allow realizing strongly correlated quantum phases and constituting a promising tool for quantum simulation of complex systems [1]. In the present work, we investigate strongly correlated Bose gases using inelastic light scattering (Bragg scattering) [2] to induce excitations with a non-zero momentum in the linear response regime. In this way, we are able to measure the excitation spectrum of the system. For a three-dimensional Bose-Einstein condensate (BEC) in the presence of a one-dimensional (1D) optical lattice we create excitations in the different Bloch bands of the periodic potential in agreement with a mean-field description [4]. To reach a range of interaction beyond the mean-field regime we create 1D BECs using a two-dimensional optical lattice. Adding a 1D optical lattice along the axis of the BECs we drive the system across the transition from superfluid to a Mott insulating state and investigate its linear response to the excitation in the different quantum states. The complexity of the strongly correlated quantum states is directly displayed in the spectra which exhibit novel features [5]. In particular, the correlated superfluid presents a spectrum characterized by an asymmetric shape in the spectrum suggesting the presence of an additional mode to the phonon mode as predicted in [6]. Moreover, for the first time in the insulating state multiple resonances has been observed which can be related to the temperature of the system [7]. - References: [1] D. Jaksch, C. Bruder, J. I. Cirac, C. W. Gardiner, and P. Zoller, Phys. Rev. Lett. 81, 3108 (1998). [2] J. Stenger, S. Inouye, A. P. Chikkatur, D. M. Stamper-Kurn, D. E. Pritchard and W. Ketterle, Phys. Rev. Lett. 82, 4569 (1999). [3] T. Stoeferle, H. Moritz, C. Schori, M. K¨ohl, and T. Esslinger, Phys. Rev. Lett. 92, 130403 (2004). [4] N. Fabbri, D. Cl´ement, L. Fallani, C. Fort, M. Modugno, K. M. R. van der Stam, and M. Inguscio, e-print arXiv:0901.1805 (2009). [5] D. Cl´ement, N. Fabbri, L. Fallani, C. Fort, and M. Inguscio, e-print arXiv:0812.4530 (2008). [6] K. Sengupta and N. Dupuis, Phys. Rev. A 71, 033629 (2005); S. D. Huber, E. Altman, H. P. Bchler, and G. Blatter, Phys. Rev. B 75, 085106 (2007); C. Menotti and N. Trivedi, Phys. Rev. B 77, 235120 (2008). [7] A. M. Rey, P. B. Blakie, G. Pupillo, C. J. Williams, and C. W. Clark, Phys. Rev. A 72, 023407 (2005).
Exploring strongly correlated Bose gases by light scattering: the superfluid to Mott insulator cross-over
Nicole Fabbri;
2009
Abstract
Ultracold gases in optical lattices allow realizing strongly correlated quantum phases and constituting a promising tool for quantum simulation of complex systems [1]. In the present work, we investigate strongly correlated Bose gases using inelastic light scattering (Bragg scattering) [2] to induce excitations with a non-zero momentum in the linear response regime. In this way, we are able to measure the excitation spectrum of the system. For a three-dimensional Bose-Einstein condensate (BEC) in the presence of a one-dimensional (1D) optical lattice we create excitations in the different Bloch bands of the periodic potential in agreement with a mean-field description [4]. To reach a range of interaction beyond the mean-field regime we create 1D BECs using a two-dimensional optical lattice. Adding a 1D optical lattice along the axis of the BECs we drive the system across the transition from superfluid to a Mott insulating state and investigate its linear response to the excitation in the different quantum states. The complexity of the strongly correlated quantum states is directly displayed in the spectra which exhibit novel features [5]. In particular, the correlated superfluid presents a spectrum characterized by an asymmetric shape in the spectrum suggesting the presence of an additional mode to the phonon mode as predicted in [6]. Moreover, for the first time in the insulating state multiple resonances has been observed which can be related to the temperature of the system [7]. - References: [1] D. Jaksch, C. Bruder, J. I. Cirac, C. W. Gardiner, and P. Zoller, Phys. Rev. Lett. 81, 3108 (1998). [2] J. Stenger, S. Inouye, A. P. Chikkatur, D. M. Stamper-Kurn, D. E. Pritchard and W. Ketterle, Phys. Rev. Lett. 82, 4569 (1999). [3] T. Stoeferle, H. Moritz, C. Schori, M. K¨ohl, and T. Esslinger, Phys. Rev. Lett. 92, 130403 (2004). [4] N. Fabbri, D. Cl´ement, L. Fallani, C. Fort, M. Modugno, K. M. R. van der Stam, and M. Inguscio, e-print arXiv:0901.1805 (2009). [5] D. Cl´ement, N. Fabbri, L. Fallani, C. Fort, and M. Inguscio, e-print arXiv:0812.4530 (2008). [6] K. Sengupta and N. Dupuis, Phys. Rev. A 71, 033629 (2005); S. D. Huber, E. Altman, H. P. Bchler, and G. Blatter, Phys. Rev. B 75, 085106 (2007); C. Menotti and N. Trivedi, Phys. Rev. B 77, 235120 (2008). [7] A. M. Rey, P. B. Blakie, G. Pupillo, C. J. Williams, and C. W. Clark, Phys. Rev. A 72, 023407 (2005).I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
