Three-body Recombination Loss Research Articles

Finite-range bias in fitting three-body loss to the zero-range model

Three-body recombination loss in ultracold atoms is a central process for studying universal few-body systems. Here, the authors discuss a systematic error that occurs when analyzing this loss mechanism with zero-range models.

P -wave Efimov physics implications at unitarity

Equal mass fermionic trimers with two different spin components near the unitary limit are shown to possess a universal van der Waals bound or resonance state near $s$-wave unitarity, when $p$-wave interactions are included between the particles with equal spin. Our treatment uses a single-channel Lennard-Jones interaction with long range two-body van der Waals potentials. While it is well-known that there is no true Efimov effect that would produce an infinite number of bound states in the unitary limit, we demonstrate that another type of universality emerges for the symmetry $L^{\Pi}=1^{-}$. The universality is a remnant of Efimov physics that exists in this system at $p$-wave unitarity, and it leads to modified threshold and scaling laws in that limit. Application of our model to the system of three lithium atoms studied experimentally by Du, Zhang, and Thomas [Phys. Rev. Lett. {\bf 102}, 250402 (2009)] yields a detailed interpretation of their measured three-body recombination loss rates.

Low-Field Feshbach Resonances and Three-Body Losses in a Fermionic Quantum Gas of 161Dy

We report on the high-resolution Feshbach spectroscopy on a degenerate, spin-polarized Fermi gas of 161Dy atoms, measuring three-body recombination losses at a low magnetic field. For field strengths up to 1 G, we identify as much as 44 resonance features and observe the plateaus of very low losses. For four selected typical resonances, we study the dependence of the threebody recombination rate coefficient on the magnetic resonance detuning and on the temperature. We observe a strong suppression of losses with decreasing temperature already for small detunings from the resonance. The characterization of complex behavior of the three-body losses of fermionic 161Dy is important for future applications of this peculiar species in research on atomic quantum gases.

Focusing of Bragg-outcoupled paraxial atom lasers

We theoretically study the focusing of a quasi-continuous atom laser beam of rubidium-85 ($^{85}$Rb). A two-sate model analysis based on the Gross-Pitaevskii equation is used which comprises the effects of two-body atom-atom interactions and three-body recombination losses. Utilizing optical focusing potentials such as harmonic potentials, the essential factors such as the width, peak density and atom loss rate of the focused atom laser beam profile are investigated. Our analysis predicts that using an atom laser offers a dramatic improvement in resolution of up to $8$ nm.

Controllable dissipative quantum droplets in one-dimensional optical lattices

We investigate the dynamics of dissipative quantum droplets (QDs) forming in one-dimensional binary Bose gases subjected to three-body recombination loss and linear gain in perturbed optical lattices . We demonstrate by a perturbation procedure that an alimentation of atoms from an external feeding source to the QDs may lead to the formation of dynamically-stabilized dissipation-controlled QDs. It is worth noting that such dissipation-controlled QDs are independent of the initial condensation norm and are solely determined by the gain and loss parameters. We further study the dynamics of the dissipation-controlled QDs with varying norm due to the gain and loss mechanisms in relatively weak optical lattices. It is found that the stationary dissipative QDs can be accelerated and either continuously travel across the potential barriers or eventually perform trapped oscillations in different lattice sites by selecting the appropriate gain and loss parameters. Finally, we deal with the collision between the dissipative QDs. It is revealed that two slowly moving dissipative QDs with varying norm may merge or collide quasi-elastically depending on their initial separation, which is quite different from QDs in the conservative systems. Specially, we explore the collision dynamics of the dissipative QDs in a single lattice site provided that the spatial period of optical lattices is large enough. The in-phase interaction between the dissipative QDs tends to merge, while the out-of-phase interaction displays quasi-elastic collision.

Optical focusing of Bose-Einstein condensates

We theoretically investigate the optical focusing of a rubidium Bose-Einstein condensate onto a planar surface. Our analysis uses a Gaussian variational method that includes the effects of two-body atom-atom interactions and three-body recombination losses. The essential factors such as the width, peak density and atom loss rate of the focused BEC profile on the surface are investigated and compared to Gross-Pitaevskii numerical simulations. We find a reasonable agreement in the results between our analytical approach and the numerical simulations. Our analysis predicts that condensates of $10^5$ atoms could be focused down to $\sim 10$nm widths, potentially allowing nanometer-scale atomic deposition with peak densities greater than $10^5$ atoms/$\mu$m$^2$.

Probing the Interface of a Phase-Separated State in a Repulsive Bose-Fermi Mixture.

We probe the interface between a phase-separated Bose-Fermi mixture consisting of a small Bose-Einstein condensate of ^{41}K residing in a large Fermi sea of ^{6}Li. We quantify the residual spatial overlap between the two components by measuring three-body recombination losses for variable strength of the interspecies repulsion. A comparison with a numerical mean-field model highlights the importance of the kinetic energy term for the condensed bosons in maintaining the thin interface far into the phase-separated regime. Our results demonstrate a corresponding smoothing of the phase transition in a system of finite size.

Collision Dynamics of Dissipative Matter-Wave Solitons in a Perturbed Optical Lattice**Supported by the National Natural Science Foundation of China under Grant Nos 11547125 and 11465008, the Hunan Provincial Natural Science Foundation under Grant Nos 2015JJ4020 and 2015JJ2114, and the Scientific Research Fund of Hunan Provincial Education Department under Grant No 14A118.

We investigate the stability and collision dynamics of dissipative matter-wave solitons formed in a quasi-one-dimensional Bose—Einstein condensate with linear gain and three-body recombination loss perturbed by a weak optical lattice. It is shown that the linear gain can modify the stability of the single dissipative soliton moving in the optical lattice. The collision dynamics of two individual dissipative matter-wave solitons explicitly depend on the linear gain parameter, and they display different dynamical behaviors in both the in-phase and out-of-phase interaction regimes.

Universality of the Three-Body Parameter for Efimov States in Ultracold Cesium

We report on the observation of triatomic Efimov resonances in an ultracold gas of cesium atoms. Exploiting the wide tunability of interactions resulting from three broad Feshbach resonances in the same spin channel, we measure magnetic-field dependent three-body recombination loss. The positions of the loss resonances yield corresponding values for the three-body parameter, which in universal few-body physics is required to describe three-body phenomena and, in particular, to fix the spectrum of Efimov states. Our observations show a robust universal behavior with a three-body parameter that stays essentially constant.

Runaway evaporation for optically dressed atoms

Forced evaporative cooling in a far-off-resonance optical dipole trap is proved to be an efficient method to produce fermionic- or bosonic-degenerated gases. However, in most of the experiments, the reduction of the potential height occurs with a diminution of the collision elastic rate. Taking advantage of a long-living excited state, like in two-electron atoms, I propose a new scheme, based on an optical knife, where the forced evaporation can be driven independently of the trap confinement. In this context, the runaway regime might be achieved leading to a substantial improvement of the cooling efficiency. The comparison with the different methods for the forced evaporation is discussed in the presence or absence of three-body recombination losses.

Nuclear-Spin-Independent Short-Range Three-Body Physics in Ultracold Atoms

We investigate three-body recombination loss across a Feshbach resonance in a gas of ultracold 7Li atoms prepared in the absolute ground state and perform a comparison with previously reported results of a different nuclear-spin state [N. Gross, Phys. Rev. Lett. 103, 163202 (2009)]. We extend the previously reported universality in three-body recombination loss across a Feshbach resonance to the absolute ground state. We show that the positions and widths of recombination minima and Efimov resonances are identical for both states which indicates that the short-range physics is nuclear-spin independent.

Dissipation-Managed Bright Soliton in a 1D Bose–Einstein Condensate in an Optical-Lattice Potential

We study the formation of a dynamically-stabilized dissipation-managed bright soliton in a quasi-one-dimensional Bose–Einstein condensate by including an imaginary three-body recombination loss term and an imaginary linear feeding one in the Gross–Pitaevskii equation, trapped in a shallow optical-lattice potential. Based on the direct approach of perturbation theory for the nonlinear Schrödinger equation, we demonstrate that the height (as well as width) of bright soliton may have little change through selecting experimental parameters.

Improving the efficiency of ultracold dipolar molecule formation by first loading onto an optical lattice

Ultracold ground state dipolar 40K-87Rb molecules have recently been produced in a loose harmonic trap by employing a magnetic field sweep across a Feshbach resonance followed by stimulated Raman adiabatic passage [K.-K. Ni et al., Science 322, 231 (2008)]. The overall experimental efficiency for molecule formation was around 20%. We show that the efficiency can be increased to nearly 100% if one first loads the atomic gases into an optical lattice of the appropriate depth and tunes the interspecies attraction to have exactly one atom of each species at an occupied lattice site. Our proposed scheme provides a large enhancement to the dipolar molecule density even at relatively high temperatures, and avoids three-body recombination loss by preventing lattice sites from being triply occupied.

Observation of Universality in UltracoldLi7Three-Body Recombination

We report on experimental evidence of universality in ultracold 7Li atoms' three-body recombination loss in the vicinity of a Feshbach resonance. We observe a recombination minimum and an Efimov resonance in regions of positive and negative scattering lengths, respectively, which are connected through the pole of the Feshbach resonance. Both observed features lie deeply within the range of validity of the universal theory, and we find that the relations between their properties, i.e., widths and locations, are in excellent agreement with the theoretical predictions.

Mott-insulator shells in the three-dimensional Bose-Hubbard model with harmonic confinement

Ultracold atom experiments offer unprecedented potential for the quantitative comparison of quantum many-body effects with theory. This comparison is hindered by the lack of numerical methods capable of dealing with these large inhomogeneous three-dimensional systems. In this paper we demonstrate the applicability of a highly efficient numerical method based on the Gutzwiller approximation for calculating the ground state of the Bose-Hubbard model in the regimes of the recent cold atom experiments. The numerical method is applied to the experimental regime employed by Campbell et al. [Science 314, 281 (2006)], where Mott-insulator shells were directly imaged via atomic clock shifts. We calculate several quantities that are closely related to the current experimental measurement methods: average number distributions, momentum distributions, two-photon spectra, and three-body recombination loss rates. Our results shed light on a number of features of the experimental observations and clarify both the crossover behavior around the superfluid--Mott-insulator transition point and the experimentally observed three-body decay rate of the Mott-insulator shells.

Hyperchaos of two coupled Bose–Einstein condensates with a three-body interaction

We investigate the dynamics of two tunnel-coupled Bose-Einstein condensates (BECs) in a double-well potential. The effects of the three-body recombination loss and the feeding of the condensates from the thermal cloud are studied in the case of attractive interatomic interaction. An imaginary three-body interaction term is considered and a two-mode approximation is used to derive three coupled equations which describe the total atomic numbers of the two condensates, the relative population and relative phase respectively. Theoretical analyses and numerical calculations demonstrate the existence of chaotic and hyperchaotic behaviour by using a periodically time-varying scattering length.

Unstable Cycle of Two Coupled Bose-Einstein Condensates with Three-Body Interaction

We investigate the dynamics of two Bose-Einstein condensates (BECs) tunnel-coupled by a double-well potential. The effects of the three-body recombination losses and the feeding of the condensates from the thermal cloud are studied in the case of attractive interatomic interaction. An imaginary three-body interaction term is considered and a two-mode approximation is used to derive three coupled equations, which describe the total atomic numbers of the two condensates, the relative population and relative phase. Theoretical analysis and numerical calculations demonstrate the existence of chaotic and unstable cycle behavior for a periodically time-varying scattering length.

The dynamics of triple-well trapped Bose–Einstein condensates with atoms feeding and loss effects

In this paper, we consider the macroscopic quantum tunnelling and self-trapping phenomena of Bose–Einstein condensates (BECs) with three-body recombination losses and atoms feeding from thermal cloud in triple-well potential. Using the three-mode approximation, three coupled Gross–Pitaevskii equations (GPEs), which describe the dynamics of the system, are obtained. The corresponding numerical results reveal some interesting characteristics of BECs for different scattering lengths. The self-trapping and quantum tunnelling both are found in zero-phase and π-phase modes. Furthermore, we observe the quantum beating phenomenon and the resonance character during the self-trapping and quantum tunnelling. It is also shown that the initial phase has a significant effect on the dynamics of the system.

Evidence for Efimov quantum states in an ultracold gas of caesium atoms

Systems of three interacting particles are notorious for their complex physical behaviour. A landmark theoretical result in few-body quantum physics is Efimov's prediction of a universal set of bound trimer states appearing for three identical bosons with a resonant two-body interaction. Counterintuitively, these states even exist in the absence of a corresponding two-body bound state. Since the formulation of Efimov's problem in the context of nuclear physics 35 years ago, it has attracted great interest in many areas of physics. However, the observation of Efimov quantum states has remained an elusive goal. Here we report the observation of an Efimov resonance in an ultracold gas of caesium atoms. The resonance occurs in the range of large negative two-body scattering lengths, arising from the coupling of three free atoms to an Efimov trimer. Experimentally, we observe its signature as a giant three-body recombination loss when the strength of the two-body interaction is varied. We also detect a minimum in the recombination loss for positive scattering lengths, indicating destructive interference of decay pathways. Our results confirm central theoretical predictions of Efimov physics and represent a starting point with which to explore the universal properties of resonantly interacting few-body systems. While Feshbach resonances have provided the key to control quantum-mechanical interactions on the two-body level, Efimov resonances connect ultracold matter to the world of few-body quantum phenomena.

Three-body recombination in two coupled Bose–Einstein condensates

We investigate the dynamics of two Bose–Einstein condensates (BECs) tunnel coupled by a double-well potential. In the case of attractive interatomic interaction, the effects of the three-body recombination losses and the feeding of the condensates from the thermal cloud are studied by using a two-mode approximation. It is shown that the stability region of the parameter space could be enlarged by increasing the three-body losses or the tunnelling coefficient. The numerical results also reveal some interesting motion characteristics of the BECs for different s-wave scattering lengths, including macroscopic quantum self-trapping of non-stationary state BECs, and periodic oscillation of the population whose phase orbit tends to a stable limit cycle.