Rate limit for photoassociation of a Bose-Einstein condensate

We simulate numerically the photodissociation of molecules into noncondensate atom pairs that accompanies photoassociation of an atomic Bose-Einstein condensate into a molecular condensate. Such rogue photodissociation sets a limit on the achievable rate of photoassociation. Given the atom density rho and mass m, the limit is approximately 6(planck)rho(2/3)/m.     

Cross-molecular coupling in combined photoassociation and Feshbach resonances

We model combined photoassociation and Feshbach resonances in a Bose-Einstein condensate. When the magnetic field is far-off resonance, cross coupling between the two target molecules--enabled by the shared dissociation continuum--leads to an anomalous dispersive shift in the position of laser resonance, as well as unprecedented elimination and enhancement of resonant photoassociation via quantum interference. For off-resonant lasers, a dispersive shift and quantum interference appear similarly in resonant three-body Feshbach losses, except that the Feshbach node is tunable with intensity.     

Two-body transients in coupled atomic-molecular bose-einstein condensates

We discuss the dynamics of an atomic Bose-Einstein condensate when pairs of atoms are converted into molecules by single-color photoassociation. Three main regimes are found, and it is shown that they can be understood on the basis of time-dependent two-body theory. In particular, the so-called rogue dissociation regime [Phys. Rev. Lett. 88, 090403 (2002)10.1103/PhysRevLett.88.090403], which has a density-dependent limit on the photoassociation rate, is identified with a transient regime of the two-atom dynamics exhibiting universal properties. Finally, we illustrate how these regimes could be explored by photoassociating condensates of alkaline-earth atoms.     

Photoassociation of a Bose-Einstein condensate near a Feshbach resonance

We measure the effect of a magnetic Feshbach resonance (FR) on the rate and light-induced frequency shift of a photoassociation resonance in ultracold 7Li. The photoassociation-induced loss-rate coefficient K_{p} depends strongly on magnetic field, varying by more than a factor of 10;{4} for fields near the FR. At sufficiently high laser intensities, K_{p} for a thermal gas decreases with increasing intensity, while saturation is observed for the first time in a Bose-Einstein condensate. The frequency shift is also strongly field dependent and exhibits an anomalous blueshift for fields just below the FR.     

Quantitative test of thermal field theory for Bose-Einstein condensates

We present numerical results from a second-order quantum field theory of Bose-Einstein condensates applied to the 1997 JILA experiment [Phys. Rev. Lett. 78, 764 (1997)]]. Good agreement is found for the energies and decay rates for both the lowest-energy m=2 and m=0 modes. The anomalous behavior of the m=0 mode is due to experimental perturbation of the noncondensate. The theory is gapless and includes the coupled dynamics of the condensate and thermal cloud, the anomalous pair average, and all relevant finite size effects.     

Superfluid bose liquid with a suppressed BEC and an intensive pair coherent condensate as a model of 4He

One introduces a model of the superfluid state of a Bose liquid with repulsion between bosons, in which at T=0, along with a weak single-particle Bose-Einstein condensate, there exists an intensive pair coherent condensate, analogous to the Cooper condensate in a Fermi liquid with attraction between fermions. A closed system of nonlinear integral equations for the normal and anomalous self-energy parts is solved numerically, and a quasiparticle spectrum is obtained, which is in good agreement with the experimental spectrum of elementary excitations in superfluid 4He. It is shown that the roton minimum in the spectrum is associated with the negative minimum of the Fourier component of the pair interaction potential.     

Photoassociation of Atomic BEC within Mean-Field Approximation： Exact Solutions

We propose an exactly solvable method to study the coherent two-colour photoassociation of an atomic Bose- Einstein condensate, by linearizing the bilinear atom-molecule coupling, which allows us to conveniently probe the quantum dynamics and statistics of the system. By preparing different initial states of the atomic condensate, we can observe very different quantum statistical properties of the system by exactly calculating the quadrature- squeezed and mode-correlated functions.     

超冷铯分子纯长程态转动常数的精密测量

利用调制的俘获损耗光谱技术实验测量了超冷铯分子纯长程0_g^-态的高分辨光谱. 采用双光缔合光谱技术构建了精确的频率差参考信号, 对转动能级的共振频率间隔进行了精确的标定, 获得了转动能级频率间隔与转动量子数的关系. 通过将实验数据拟合到非刚性转动模型, 获得了超冷铯分子纯长程0_g^-态不同振动态的转动常数. 实验结果表明转动常数随振动量子数的增加而线性减小, 线性递减率为-0.41 MHz±0.01 MHz. 关键词： 双光缔合光谱技术 超冷铯分子 转动常数 纯长程态     

量子遂穿在双阱异核分子形成过程中的作用(英文）

对于束缚在双阱中的两组分玻色－爱因斯坦凝聚体,本文研究了基于光缔合机制形成分子的过程中,量子隧穿所起的作用．该双阱外势可以在实验上利用磁场生成的谐振子势和由蓝失谐光或射频源生成的中心势垒来实现．在合适的光场中,我们分析了系统在不同初始状态下的短时极限量子动力学,同时对系统做了在平均场近似下的数值计算分析．我们发现无论是隧穿强度还是初始状态的制备都对系统的动力学有很大的影响．我们还计算了同核分子在这些情况下的结果,并和异核分子计算的结果作了比较．量子化的光缔合光场在分子形成过程的影响也在文章中给予了讨论．     

Jaynes-Cummings dynamics with a matter wave oscillator

We propose to subject two Bose-Einstein condensates to a periodic potential, so that one condensate undergoes the Mott-insulator transition to a state with precisely one atom per lattice site. We show that photoassociation of heteronuclear molecules within each lattice site is described by the quantum optical Jaynes-Cummings Hamiltonian. In analogy with studies of this Hamiltonian with cavity fields and trapped ions, we are thus able to engineer quantum optical states of atomic matter wave fields and we are able to reconstruct these states by quantum state tomography.     

Anomalous modes drive vortex dynamics in confined Bose-Einstein condensates

The dynamics of vortices in trapped Bose-Einstein condensates are investigated both analytically and numerically. In axially symmetric traps, the critical rotation frequency for metastability of an isolated vortex coincides with the largest vortex precession frequency (or anomalous mode) in the Bogoliubov excitation spectrum. The number of anomalous modes increases for an elongated condensate. The largest mode frequency exceeds the thermodynamic critical frequency and the nucleation frequency at which vortices are created dynamically. Thus, anomalous modes describe both vortex precession and the critical rotation frequency for creation of the first vortex in an elongated condensate.     

All-optical formation of molecules with spin degree of freedom in an atomic Bose-Einstein condensate

We have performed a two-photon photoassociation experiment in an atomic Bose-Einstein condensate of ⁸⁷Rb with the spin degree of freedom, which is created by an all-optical method with CO₂ lasers. The spinor character of the created molecules has been revealed by the photoassociation spectrum with a new structure. The hyperfine structure of the created molecules near the dissociation limit is identified by observations of the Zeeman and AC-Stark effects of the molecules. We have also demonstrated the spin-selective creation of molecules. This result would open the new possibility of research on novel molecular spinor BEC.     

超低频调制光缔合光谱的实验研究

通过激光冷却技术在磁光阱中俘获原子数约107,温度约200 μK,直径约400 μm的超冷铯原子,利用超冷铯原子光缔合方法制备了激发态的超冷铯分子。实验研究了光缔合光不同扫描速率对铯分子振转光谱分辨率的影响,发现光缔合光扫描速率较慢时,铯分子振转光谱分辨率较高。通过高灵敏的雪崩光电探测器探测冷原子荧光,获得了超冷铯分子第一激发态6S_1/2+6P_3/2离解限0-_g长程态高分辨振转光谱。为了实现受控拉曼光缔合制备超冷基态分子,光缔合激光频率需要锁定在原子-分子共振跃迁线,对超冷原子光缔合光谱进行了超低频波长调制,通过改变调制幅度和调制频率获得最优化的一阶微分信号,将该信号反馈回激光器,实现闭合环路稳频,满足了受控拉曼光缔合制备振转能级可控的基态分子的实验要求,该工作对研究受限空间中的超冷原子分子具有很重要的意义。     

Spinor molecule in atomic Bose–Einstein condensate

We have performed two-photon photoassociation experiments in atomic Bose–Einstein condensate (BEC) of ⁸⁷Rb with spin degree of freedom which is created by all-optical method with CO₂ lasers. The spinor character of the molecules has been revealed by the photoassociation spectrum with a new structure. The hyperfine structure of the molecules near the dissociation limit is identified by observations of the Zeeman and AC-Stark effects of the molecules. The molecules have been spin-selectively probed by the use of the light shift. This result would open the new possibility of research on novel spinor molecular BEC.     

Quantum phases of Bose gases on a lattice with pair-tunneling

We investigate the strongly interacting lattice Bose gases on a lattice with two-body interaction of nearest neighbors characterized by pair tunneling.The excitation spectrum and the depletion of the condensate of lattice Bose gases are investigated using the Bogoliubov transformation method and the results show that there is a pair condensate as well as a single particle condensate.The various possible quantum phases,such as the Mott-insulator phase(MI),the superfluid phase(SF) of an individual atom,the charge density wave phase(CDW),the supersolid phase(SS),the pair-superfluid(PSF) phase,and the pair-supersolid phase(PSS) are discussed in different parametric regions within our extended Bose-Hubbard model using perturbation theory.     

The quantum pressure correction to the excitation spectrum of the trapped superfluid Fermi gases in a BEC-BCS crossover

Using quantum hydrodynamic approaches, we study the quantum pressure correction to the collective excitation spectrum of the interacting trapped superfluid Fermi gases in the BEC-BCS crossover. Based on a phenomenological equation of state, we derive hydrodynamic equations of the system in the whole BEC-BCS crossover regime. Beyond the Thomas--Fermi approximation, expressions of the frequency corrections of collective modes for both spherical and axial symmetric traps excited in the BEC-BCS crossover are given explicitly. The corrections of the eigenfrequencies due to the quantum pressure and their dependence on the inverse interaction strength, anisotropic parameter and particle numbers of the condensate are discussed in detail.     

Creation of a molecular condensate by dynamically melting a Mott insulator

We propose the creation of a molecular Bose-Einstein condensate by loading an atomic condensate into an optical lattice and driving it into a Mott insulator with exactly two atoms per site. Molecules in a Mott insulator state are then created under well defined conditions by photoassociation with essentially unit efficiency. Finally, the Mott insulator is melted and a superfluid state of the molecules is created. We study the dynamics of this process and photoassociation of tightly trapped atoms.     

Creation of Molecular Vortex

The molecular vortex is predicted to be generated from an atomic Bose-Einstein condensate through the two-color photoassociation process with a specially designed field configuration in which a Gaussian and a first-order Laguerre Gaussian laser beam are applied between the bound-bound and free-bound transition, respectively. We show that such a configuration can lead to a coherent superposition of an atomic condensate and a molecular quantized vortex. We develop stimulated adiabatic passages to minimize the effect of mean-field shifts due to collisions for optimal conversi9n of an atomic condensate into a ground molecular vortex.     

Langevin Equation of Collective Modes of Bose–Einstein Condensates in Traps

A quantum Langevin equation for the amplitudes of the collective modes in Bose–Einstein condensate is derived. The collective modes are coupled to a thermal reservoir of quasi-particles, whose elimination leads to the quantum Langevin equation. The dissipation rates are determined via the correlation function of the fluctuating force and are evaluated in the local-density approximation for the spectrum of quasi-particles and the Thomas–Fermi approximation for the condensate.I take great pleasure in dedicating this paper to Gregoire Nicolis on the occasion of his sixtieth birthday.     

超冷铯分子0g-长程态的振转光谱研究

通过超冷铯原子光缔合制备激发态的超冷铯分子. 利用冷原子荧光频率调制技术获得了超冷铯分子第一激发态6S_1/2+6P_3/2离解限0_g^-长程态高分辨振转光谱, 计算得到0_g^- 长程态振动量子数从0到51的不同振动能级的转动常数, 和Daniel研究小组的理论结果符合得很好. 关键词： 超冷铯分子 光缔合 振转光谱