## SCL Seminar by Javed Akram

SCL seminar of the Center for the Study of Complex Systems, will be held on Thursday, 24 August 2017 at 14:00 in the library reading room “Dr. Dragan Popović" of the Institute of Physics Belgrade. The talk entitled

will be given by Dr. Javed Akram (COMSATS Institute of Information Technology, Islamabad, Pakistan).

We will present a detailed theoretical study on tuning both static and dynamic properties of quasi-one-dimensional trapped Bose-Einstein condensates (BECs). At first, we will discuss Rb atoms in a quasi-one-dimensional trap geometry, which consists of a harmonic trap plus a red or blue-detuned Gaussian (Hermite-Gaussian) dimple trap [1]. After having switched off the dimple trap, shock waves or gray pair-soliton (bi-)trains emerge, which oscillates with a characteristic frequency in the remaining harmonic trap. Afterwards, we will investigate how the wave function of a trapped Rb BEC changes due to the presence of a single Cs impurity [2]. To this end, we will determine the equilibrium phase diagram, which is spanned by the intra- and inter-species coupling strengths. In addition, once the attractive or repulsive interspecies coupling strength is switched off, we will see that white shock waves or bi-solitons emerge. This is a phenomenon similar to a BEC in an optical dipole trap, although this time we will not see bi-soliton trains but only bi-solitons. Afterwards, we will analyze a quasi-one-dimensional BEC in a nonlinear gravito-optical surface trap [3]. We will calculate a non-ballistic expansion of the BEC cloud, when the confining evanescent laser beam is shut off, and check if the results agree with previously obtained experimental results of the Innsbruck experiment [4].

[1] J. Akram and A. Pelster, Phys. Rev. A 93, 023606 (2016); Laser Phys. 26, 065501 (2016).

[2] J. Akram and A. Pelster, Phys. Rev. A 93, 033610 (2016).

[3] J. Akram, et al., J. Phys. B: At. Mol. Opt. Phys. 49, 075302 (2016).

[4] D. Rychtarik et al., Phys. Rev. Lett. 92, 173003 (2004).

**"****Tuning Static and Dynamic Properties of a Quasi-One-Dimensional Bose-Einstein Condensate"**will be given by Dr. Javed Akram (COMSATS Institute of Information Technology, Islamabad, Pakistan).

**Abstract of the talk:**We will present a detailed theoretical study on tuning both static and dynamic properties of quasi-one-dimensional trapped Bose-Einstein condensates (BECs). At first, we will discuss Rb atoms in a quasi-one-dimensional trap geometry, which consists of a harmonic trap plus a red or blue-detuned Gaussian (Hermite-Gaussian) dimple trap [1]. After having switched off the dimple trap, shock waves or gray pair-soliton (bi-)trains emerge, which oscillates with a characteristic frequency in the remaining harmonic trap. Afterwards, we will investigate how the wave function of a trapped Rb BEC changes due to the presence of a single Cs impurity [2]. To this end, we will determine the equilibrium phase diagram, which is spanned by the intra- and inter-species coupling strengths. In addition, once the attractive or repulsive interspecies coupling strength is switched off, we will see that white shock waves or bi-solitons emerge. This is a phenomenon similar to a BEC in an optical dipole trap, although this time we will not see bi-soliton trains but only bi-solitons. Afterwards, we will analyze a quasi-one-dimensional BEC in a nonlinear gravito-optical surface trap [3]. We will calculate a non-ballistic expansion of the BEC cloud, when the confining evanescent laser beam is shut off, and check if the results agree with previously obtained experimental results of the Innsbruck experiment [4].

[1] J. Akram and A. Pelster, Phys. Rev. A 93, 023606 (2016); Laser Phys. 26, 065501 (2016).

[2] J. Akram and A. Pelster, Phys. Rev. A 93, 033610 (2016).

[3] J. Akram, et al., J. Phys. B: At. Mol. Opt. Phys. 49, 075302 (2016).

[4] D. Rychtarik et al., Phys. Rev. Lett. 92, 173003 (2004).