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Bose-Einstein Condensation in Optical Lattices

Author: XiaoFei
Tutor: HuSongQing；WangWenXin
School: China University of Petroleum
Course: Materials Science and Engineering
Keywords: Bose - Einstein condensate Optical lattice Thermodynamic Properties Ground-state properties Gross-Pitaevskii equation
CLC: O431.2
Type: Master's thesis
Year: 2010
Downloads: 109
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Abstract


Bose - Einstein condensate (BEC) as a new form of matter, is a research hotspot in recent years, one of the physics community. Bose - Einstein condensates basic features are: When Bose gas temperature below the critical temperature, the macroscopic magnitude boson will gather in the lowest energy macroscopic quantum coherent state (ground state). Bose - Einstein condensate, all particles are in the lowest energy state, and have the same physical characteristics, just use a wave function to describe. Realization of an optical lattice BEC people study opens up new directions. Currently cold atoms in optical lattices cold atom manipulation has become an important topic in the application control optical lattice atomic Bose - Einstein condensates research has made a breakthrough in quantum computing, quantum information and quantum transport so has a broad application prospects. Firstly, the use of methods of statistical mechanics to study ultracold atomic Bose gas to the system during loading optical lattice thermodynamic properties of Bose systems calculate the total number of particles, the critical temperature, the base rate and the internal energy states occupy a constant volume heat capacity, entropy and other thermodynamic variables, during loading of the amount of change of the thermodynamic characteristics and stability of the system near the critical temperature. Study found that: When (T Tc) are the same, in a harmonic trap ground state occupies rates than large optical lattices, gather system more stable; condensates with Tα 1 internal energy U is proportional constant volume heat capacity CV and Tα into proportional; ultracold atomic Bose gas to slow adiabatic optical lattice loading process, the entropy of the system remains the same; if (T Tc) is less than 0.30, with the load intensity increases, the ground state occupy the rate becomes larger, the more system stability, however, when (T Tc) is greater than 0.70, the strength increases with the loading, Bose system becomes unstable. Bose - Einstein condensate meet Gross-Pitaevskii equation. Finally, by solving the Gross-Pitaevskii equation to study the optical lattice Bose - Einstein condensates in the ground state properties, solving different potential depth of the optical lattice potential field next condensates ground state wave function and energy. The results showed that: the ground state wave function at the corresponding peak optical lattice potential field of the trough, the trough system potential field low energy particles appear a great chance, the greater the particle number density, the more stable the system; With Light lattice potential field increases, the ground state wave function of the peak growing, more and more small valley, optical lattice potential field to a certain extent, the number of particles in each grid point towards equilibrium; With optical crystal lattice potential field increases, the optical lattice condensates ground state energy of the first excited state energy decreases; Bose - Einstein condensates appear in the band structure bandgap energy band number is smaller, energy band the width of the smaller, the greater the density of states; agglomerates energy with the increase of the number of particles, which with the previous analysis of the thermodynamic properties of the process the same conclusion.

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CLC: > Mathematical sciences and chemical > Physics > Optics > The light nature of the theory > Quantum optics
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