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中国物理学会期刊

一维接触排斥相互作用单自旋翻转费米气体的基态和淬火动力学性质

CSTR: 32037.14.aps.73.20231425

Properties of ground state and quench dynamics of one-dimensional contact repulsive single-spin flipped Fermi gases

CSTR: 32037.14.aps.73.20231425
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  • 基于严格解方法, 研究了一维排斥相互作用单自旋翻转费米气体的基态和淬火动力学性质. 借助Bethe波函数, 基态和不同本征态之间的单体关联函数和两体关联函数可以表示为简单函数之和, 这一简洁形式可以极大地降低计算难度. 系统初始状态为无相互作用的基态, 当迅速把相互作用强度调节为有限大时, 动量分布和关联函数出现周期性的振荡行为; 当相互作用调节为比较弱时, 振荡周期性好且振荡幅度小, 系统可以用二能级模型近似; 当相互作用调为非常强时, 振荡周期性变差且振荡幅度大, 但是依然存在主周期. 此时整体偏离初态较远, 但是在时间为 mL^2/(2\pi\hbar)时系统非常接近初态.

     

    Based on the exact solution method, the ground state and quench dynamics properties of one-dimensional single-spin flipped Fermi gas with repulsion interaction are studied. With the Bethe wave function, the single-body correlation function and two-body correlation function of the ground state and those between different eigen-states can be reduced into a summation of simple functions, thereby greatly reducing the computational difficulty. For the system in the ground state, the single-body correlation functions and two-body correlation functions as well as momentum distributions for spin-up particles are investigated in real space with different interaction strengths. As the interaction strength increases, the number of nodes in the single-body correlation function remains unchanged, while the amplitude of oscillation decreases. Meanwhile, the number of peaks in the two-body correlation function increases by one due to interaction, indicating that the spin-down particle behaves as a spin-up particle. The momentum distribution becomes more smooth around Fermi surface with the interaction strength increasing. The interaction quench dynamics is investigated. The system is prepared in the ground state of ideal Fermi gas, and then the interaction strength is quenched to a finite positive value. The system evolves under time-dependent Schrödinger equation. The overlap between the initial state and eigen-state of post-quench interaction strength is expressed in the form of continued multiplication. The square of the modulus of this overlap, which represents the occupation probability, is calculated. We find that the occupation probabilities of the ground state and doubly degenerated excited state always have the first and the second largest value for an arbitrary interaction strength, respectively, which means that the difference in eigenenergy between these two states gives the primary period of oscillation. For relatively large particle number ( N\geqslant10), the primary period always does not change under different interaction strengths.It is found that in the case of interaction quenching, the momentum distribution and the correlation function show periodic oscillations. When the interaction strength is adjusted to a relatively small value, the oscillation periodicity is well-defined and the oscillation amplitude is small. The system can be approximated by a two-level model. When the interaction strength increases to a very large value, the oscillation periodicity worsens and the amplitude increases, but a primary period remains unchanged. Although the overall deviation is far from the initial state, it is very close to the initial state at time t=mL^2/(2\pi\hbar). This is because the difference between most energy eigenvalues is almost an integral multiple of energy unit 2\times\left(2\pi/L\right)^2.

     

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