Abstract
In this work, we use inelastic scattering of light to study the response of inhomogeneous Mott-insulator gases to external excitations. The experimental setup and procedure to probe the atomic Mott states are presented in detail. We discuss the link between the energy absorbed by the gases and accessible experimental parameters as well as the linearity of the response to the scattering of light. We investigate the excitations of the system in multiple energy bands and a band-mapping technique allows us to identify band and momentum of the excited atoms. In addition, the momentum distribution in the Mott states that is spread over the entire first Brillouin zone enables us to reconstruct the dispersion relation in the high energy bands using a single Bragg excitation with a fixed momentum transfer.
Highlights
Used to measure the excitation spectrum of inhomogeneous MI states [20]
We plot the energy transfer hν given by the Bragg beams as a function of the momentum of the excited atoms measured using the band-mapping technique. These results are compared with the dispersion relation of single particles in the presence of a periodic potential with an amplitude sy = 10 showing a good agreement5. This demonstrates that: (i) the excitations observed over a large energy scale between 27 and kHz correspond to transition towards the third energy band of the optical lattice; (ii) the quasi-momentum distribution of the inhomogeneous MI state extends over the entire lowest lattice band since the entire energy band can be mapped using a Bragg excitation with a fixed momentum transfer hq0,y
We have measured the response of bosonic MI states to excitations induced by inelastic scattering of light
Summary
The result of weak inelastic scattering of waves or particles by many-body systems may be described within the Born approximation and expressed in terms of the dynamic structure factor S [27]. Inelastic light scattering has been applied to gaseous Bose–Einstein condensates (BECs) to measure the dynamic structure factor [29]–[31] This scattering technique, referred to as Bragg spectroscopy, consists in a two-photon transition between two different momentum states of the same internal ground state [29]. Bragg spectroscopy is used as a tool to coherently manipulate atomic clouds for interferometric schemes ([37] and references therein) or for thermodynamics studies [38, 39] It has succeeded in providing novel information about strongly interacting 3D Bose [40] and Fermi [41] gases close to Feshbach resonances as well as correlated 1D Bose gases across the transition from the SF to the MI state [20]
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