Ultra-cold atomic gases provide a new chance to study the universal critical behavior of phase transition. We study theoretically the matter wave interference for ultra-cold Bose gases in the critical regime. We demon...Ultra-cold atomic gases provide a new chance to study the universal critical behavior of phase transition. We study theoretically the matter wave interference for ultra-cold Bose gases in the critical regime. We demonstrate that the interference in the momentum distribution can be used to extract the correlation in the Bose gas. A simple relation between the interference visibility and the correlation length is found and used to interpret the pioneering experiment about the critical behavior of dilute Bose gases [Science 315 1556（2007）]. Our theory paves the way to experimentally study various types of ultra-cold atomic gases with the means of matter wave interference.展开更多
We study the quantum phase transition from a superfluid to a Mott insulator of ultracold atoms in a threedimensional optical lattice with adjustable filling factors.Based on the density-adjustable Bose-Einstein conden...We study the quantum phase transition from a superfluid to a Mott insulator of ultracold atoms in a threedimensional optical lattice with adjustable filling factors.Based on the density-adjustable Bose-Einstein condensate we prepared,the excitation spectrum in the superfluid and the Mott insulator regime is measured with different ensemble-averaged filling factors.We show that for the superfluid phase,the center of the excitation spectrum is positively correlated with the ensemble-averaged filling factor,indicating a higher sound speed of the system.For the Mott insulator phase,the discrete feature of the excitation spectrum becomes less pronounced as the ensemble-averaged filling factor increases,implying that it is harder for the system to enter the Mott insulator regime with higher filling factors.The ability to manipulate the filling factor affords further potential in performing quantum simulation with cold atoms trapped in optical lattices.展开更多
We study the spatial periodicity effects on the differential light shift of noninteracting atoms in an optical lattice.Through the Rabi-spectrum approach,when the wavelength of the optical lattice is not magic,a reduc...We study the spatial periodicity effects on the differential light shift of noninteracting atoms in an optical lattice.Through the Rabi-spectrum approach,when the wavelength of the optical lattice is not magic,a reduction to the differential light shift is expected.The reduction results from the Bloch bands induced by the quantized motion in the periodic potential.Taking the microwave transition of rubidium atoms as an example,this reduction at some wavelengths can reach one order of magnitude,compared to the data without considering the spatial profile of the optical lattice.When the atomic temperature is considered,the differential light shift increases or decreases with temperature,depending on the wavelength of the lattice.Our results should be beneficial for microwave optical lattice clock and precision measurements.展开更多
We report the experimental observation of two-dimensional Talbot effect when a resonance plane wave interacts with a two-dimensional atomic density grating generated by standing wave manipulation of ultracold Bose gas...We report the experimental observation of two-dimensional Talbot effect when a resonance plane wave interacts with a two-dimensional atomic density grating generated by standing wave manipulation of ultracold Bose gases. Clear self-images of the grating and sub-images with reversed phase or fractal patterns are observed. By calculating the autocorrelation functions of the images, the behavior of periodic Talbot images is studied. The Talbot effect with two-dimensional atomic density grating expands the applications of the Talbot effect in a wide variety of research fields.展开更多
基金Project supported by the National Natural Science Foundation of China(Grant Nos.11504328,11274024,and 11334001)the National Basic Research Program of China(Grants Nos.2013CB921903 and 2012CB921300)
文摘Ultra-cold atomic gases provide a new chance to study the universal critical behavior of phase transition. We study theoretically the matter wave interference for ultra-cold Bose gases in the critical regime. We demonstrate that the interference in the momentum distribution can be used to extract the correlation in the Bose gas. A simple relation between the interference visibility and the correlation length is found and used to interpret the pioneering experiment about the critical behavior of dilute Bose gases [Science 315 1556（2007）]. Our theory paves the way to experimentally study various types of ultra-cold atomic gases with the means of matter wave interference.
基金Supported by the National Natural Science Foundation of China(Grant Nos.61703025,91736208,1150432&and 11920101004)the National Program on Key Basic Research Project of China(Grant Nos.2016YFA0301501 and 2017YFA0304204).
文摘We study the quantum phase transition from a superfluid to a Mott insulator of ultracold atoms in a threedimensional optical lattice with adjustable filling factors.Based on the density-adjustable Bose-Einstein condensate we prepared,the excitation spectrum in the superfluid and the Mott insulator regime is measured with different ensemble-averaged filling factors.We show that for the superfluid phase,the center of the excitation spectrum is positively correlated with the ensemble-averaged filling factor,indicating a higher sound speed of the system.For the Mott insulator phase,the discrete feature of the excitation spectrum becomes less pronounced as the ensemble-averaged filling factor increases,implying that it is harder for the system to enter the Mott insulator regime with higher filling factors.The ability to manipulate the filling factor affords further potential in performing quantum simulation with cold atoms trapped in optical lattices.
基金Supported by the National Basic Research Program of China under Grant No 2011CB921501the National Natural Science Foundation of China under Grant Nos 61027016,61078026,10874008 and 10934010.
文摘We study the spatial periodicity effects on the differential light shift of noninteracting atoms in an optical lattice.Through the Rabi-spectrum approach,when the wavelength of the optical lattice is not magic,a reduction to the differential light shift is expected.The reduction results from the Bloch bands induced by the quantized motion in the periodic potential.Taking the microwave transition of rubidium atoms as an example,this reduction at some wavelengths can reach one order of magnitude,compared to the data without considering the spatial profile of the optical lattice.When the atomic temperature is considered,the differential light shift increases or decreases with temperature,depending on the wavelength of the lattice.Our results should be beneficial for microwave optical lattice clock and precision measurements.
基金Supported by the State Key Development Program for Basic Research of China under Grant No 2016YFA0301501the National Natural Science Foundation of China under Grant Nos 11504328,61475007,11334001 and 91336103
文摘We report the experimental observation of two-dimensional Talbot effect when a resonance plane wave interacts with a two-dimensional atomic density grating generated by standing wave manipulation of ultracold Bose gases. Clear self-images of the grating and sub-images with reversed phase or fractal patterns are observed. By calculating the autocorrelation functions of the images, the behavior of periodic Talbot images is studied. The Talbot effect with two-dimensional atomic density grating expands the applications of the Talbot effect in a wide variety of research fields.
