Finite Pulse Ratchet Effect of Cold Atoms

Chung, Gyang Davou (2021-03-23)


The thesis presents the modelling and simulation of the rachet effect created by a spatio temporal asymmetry potential. The potential is a coupled spatial asymmetry sin wave and a rectangular pulse train. The effective Planck’s constant 𝓀(kbar), was the indicator of the quantum nature of the system and influence the dynamic of the system. The effective kick strength Ξ“, the duty cycle of the pulse train 𝜏 and 𝓀 are the key parameters that determine the possibility of directed transport in the cold atom system. The developed approach was justified by the results obtained at 𝜏 = 0.01. This result approaches those of delta pulses that were already available. It was discovered that, the variation in pulse width as indicated by the values of 𝜏 influence the system dynamics. In such a way that at 𝛤 = 4.5, with increase in Ο„ (from 0.01 to 0.03) within the studied region of 𝓀/𝜋 = 0 to 4.9, the absolute amplitude current at resonance decreases as kbar relatively increases. Although within a relatively lower values of kbar, the current has higher values for higher Ο„, before the gradual decrease as kbar increases. And it was also shown that at a fixed resonance point (kbar/pi =1.5), the ratchet current reasonably increases rapidly with increase of both Ο„ and the kicked strength 𝛤