Three-body Loss Research Articles

Strongly Anisotropic Vortices in Dipolar Quantum Droplets.

We construct strongly anisotropic quantum droplets with embedded vorticity in the 3D space, with mutually perpendicular vortex axis and polarization of atomic magnetic moments. Stability of these anisotropic vortex quantum droplets (AVQDs) is verified by means of systematic simulations. Their stability area is identified in the parametric plane of the total atom number and scattering length of the contact interactions. We also construct vortex-antivortex-vortex bound states and find their stability region in the parameter space. The application of a torque perpendicular to the vorticity axis gives rise to robust intrinsic oscillations or rotation of the AVQDs. The effect of three-body losses on the AVQD stability is considered too. The results show that the AVQDs can retain the topological structure (vorticity) for a sufficiently long time if the scattering length exceeds a critical value.

Observation of Bose-Einstein condensation of dipolar molecules.

Ensembles of particles governed by quantum mechanical laws exhibit intriguing emergent behaviour. Atomic quantum gases1,2, liquid helium3,4 and electrons in quantum materials5-7 all exhibit distinct properties because of their composition and interactions. Quantum degenerate samples of ultracold dipolar molecules promise the realization of new phases of matter and new avenues for quantum simulation8 and quantum computation9. However, rapid losses10, even when reduced through collisional shielding techniques11-13, have so far prevented evaporative cooling to a Bose-Einstein condensate (BEC). Here we report on the realization of a BEC of dipolar molecules. By strongly suppressing two- and three-body losses viaenhanced collisional shielding, we evaporatively cool sodium-caesium molecules to quantum degeneracy and cross the phase transition to aBEC. The BEC reveals itself by a bimodal distribution when the phase-space density exceeds 1. BECs with a condensate fraction of 60(10)% and a temperature of 6(2) nK are created and found to be stable with a lifetime close to 2 s. This work opens the door to the exploration of dipolar quantum matter in regimes that have been inaccessible so far, promising the creation of exotic dipolar droplets14, self-organized crystal phases15 and dipolar spin liquids in optical lattices16.

Bose-Einstein condensation of non-ground-state caesium atoms

Bose-Einstein condensates of ultracold atoms serve as low-entropy sources for a multitude of quantum-science applications, ranging from quantum simulation and quantum many-body physics to proof-of-principle experiments in quantum metrology and quantum computing. For stability reasons, in the majority of cases the energetically lowest-lying atomic spin state is used. Here, we report the Bose-Einstein condensation of caesium atoms in the Zeeman-excited mf = 2 state, realizing a non-ground-state Bose-Einstein condensate with tunable interactions and tunable loss. We identify two regions of magnetic field in which the two-body relaxation rate is low enough that condensation is possible. We characterize the phase transition and quantify the loss processes, finding unusually high three-body losses in one of the two regions. Our results open up new possibilities for the mixing of quantum-degenerate gases, for polaron and impurity physics, and in particular for the study of impurity transport in strongly correlated one-dimensional quantum wires.

Non-Hermitian p -wave superfluid and effects of the inelastic three-body loss in a one-dimensional spin-polarized Fermi gas

We theoretically investigate non-Hermitian p-wave Fermi superfluidity in one-dimensional spin-polarized Fermi gases which is relevant to recent ultracold atomic experiments. Considering an imaginary atom-dimer coupling responsible for the three-body recombination process in the Lindblad formalism, we discuss the stability of the superfluid state against the atomic loss effect. Within the two-channel non-Hermitian BCS-Eagles-Leggett theory, the atomic loss is characterized by the product of the imaginary atom-dimer coupling and the p-wave effective range. Our results indicate that for a given imaginary atom-dimer coupling, a smaller magnitude of the effective ranges of p-wave interaction is crucial for reaching the non-Hermitian p-wave Fermi superfluid state. Moreover, our theoretical framework for many-body systems with the three-body loss, which is inevitable in ultracold atoms, would promote further progress in non-Hermitian cold-atomic physics. Published by the American Physical Society 2024

Cavitation erosion resistance and tribological performance of PAI/PI/EP soft coating on 20CrMo

A polyamide-imine/polyimide/epoxy resin polymer coating is prepared on the surface of 20CrMo steel by liquid spraying technology which is used to replace the CuPb24Sn copper alloy in valve plates for pumps. Tribological and anti-cavitation erosive experiments of the polymer coating, 20CrMo steel and CuPb24Sn copper alloy are carried out under oil, oil + seawater + silt mixed environment and seawater + silt environment. The results demonstrate that the deposition coating on 20CrMo steel can effectively replace copper alloy for the valve plate of the pump under oil lubrication, oil + seawater + silt environment. Under oil lubrication, the coating exhibits adhesive wear and its average frictional coefficient is 36.63 % and 8.57 % lower than that of the steel and copper alloy, respectively. Likewise, the coating mainly exhibits abrasive wear under the complex working conditions of seawater + silt + oil and seawater + silt. The soft coating reduces the three-body wear and the three-body frictional loss due to the embeddability. Under the complex conditions of seawater + silt + oil, the cavitation mass loss of the coating is 20 % and 35.48 % lower than that of the steel substrate and copper alloy, respectively. In addition, the cavitation mass loss of the coating is 53.6 % and 62.09 % lower than that of the steel and copper alloy under the condition of seawater + silt, respectively. The main influencing factors of the aforementioned results are the lipophilicity of the coating, the large ratio of hardness to elastic modulus (H/E) and the good corrosion resistance.

High efficient Raman sideband cooling and strong three-body recombination of atoms

We report a highly efficient three-dimensional degenerated Raman sideband cooling (3D dRSC) that enhances the loading of a magnetically levitated optical dipole trap, and observe the strong atom loss due to the three-body recombination. The 3D dRSC is implemented to obtain 5 × 107 Cs atoms with the temperature of ∼ 480 nK. The cold temperature enables 1.8 × 107 atoms loaded into a crossed dipole trap with an optimized excessive levitation magnetic gradient. Compared to the loading of atoms from a bare magneto-optical trap or the gray-molasses cooling, there is a significant increase in the number of atoms loaded into the optical dipole trap. We derive for the three-body recombination coefficient of L 3 = 7.73 × 10−25 cm6/s by analyzing the strong atom loss at a large scattering length of 1418 Bohr radius, and discover the transition from the strong three-body loss to the dominant one-body loss. Our result indicates that the lifetime of atoms in the optical dipole trap is finally decided by the one-body loss after the initial strong three-body loss.

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.

Two-Body and Three-Body Abrasive Wear Behaviors of Fe-2wt%B Alloy Modified With Various K2SO4 Additions

Fe-B alloy is a candidate for a low-cost wear-resistant material but shows very low fracture toughness. To improve the toughness of Fe-B alloys, for this study we attempted to break the continuous network of eutectic Fe2B via K2SO4 addition and heat treatment, so that the Fe2B particles transform to be more spherical. The microstructure, mechanical properties, and two-body and three-body abrasive wear behaviors of the alloys modified with various K2SO4 additions were systemically investigated. The results show that the heat-treated alloys mainly consist of martensite and M2B (M = Cr, Mn, Fe, etc.). With the addition of K2SO4, a new phase α-MnS forms in the alloy, and the circularity value of M2B increases from 0.13 to 0.44. The impact toughness of alloy increases from 6.09 J/cm2 to 14.72 J/cm2 with an increment of 142%, although the Rockwell hardness does not show obvious change. Meanwhile, the two-body wear weight loss of alloys exhibits a “decrease and then increase” trend with increasing K2SO4 addition, while the three-body wear weight loss decreases first and then remains unchanged. The different wear behaviors were investigated and discussed.

Anomalous loss behavior in a single-component Fermi gas close to a p -wave Feshbach resonance

We theoretically investigate three-body losses in a single-component Fermi gas near a $p$-wave Feshbach resonance in the interacting, non-unitary regime. We extend the cascade model introduced by Waseem \textit{et al.} [M. Waseem, J. Yoshida, T. Saito, and T. Mukaiyama, Phys. Rev. A \textbf{99}, 052704 (2019)] to describe the elastic and inelastic collision processes. We find that the loss behavior exhibits a $n^3$ and an anomalous $n^2$ density dependence for a ratio of elastic-to-inelastic collision rate larger and smaller than 1, respectively. The corresponding evolutions of the energy distribution show collisional cooling or evolution toward low-energetic non-thermalized steady states, respectively. These findings are particularly relevant for understanding atom loss and energetic evolution of ultracold gases of fermionic lithium atoms in their ground state.

Collisional dynamics of two-dimensional vortex quantum droplets

A quantum droplet is a self-bound state balanced by the mean-field interaction and Lee–Huang–Yang correction in a Bose–Bose mixture. In this paper, we study the collisional dynamics of two-dimensional quantum droplets with a vortex. By adjusting the initial momentum, the initial phase difference, the topological charge of the quantum droplets, and the total number of particles, we identify three dynamic mechanisms of collisions, namely, splitting, no-splitting, and their crossover according to the states after collision, which are significantly different from the merging, separation, and evaporation of the collisional dynamics of vortex-free droplets. The initial phase difference of the two droplets changes the interference fringes and the manner of splitting of the droplets. We also show that the three-body loss of atoms does not affect the result.

Classical-linear-chain behavior from dipolar droplets to supersolids

We investigate the classicality of linear dipolar droplet arrays through a normal mode analysis of the dynamical properties in comparison to the supersolid regime. The vibrational patterns of isolated-droplet crystals that time-evolve after a small initial kick closely follow the properties of a linear droplet chain. For larger kick velocities, however, droplets may coalesce and separate again, showing distinct deviations from classicality. In the supersolid regime the normal modes are eliminated by a counterflow of mass between the droplets, signaled by a reduction of the center-of-mass motion. Our study effectively captures the vibrational patterns of isolated droplets in the presence of three-body loss and can be generalized to systems with a larger number of droplet arrays.

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.

Pinpointing Feshbach resonances and testing Efimov universalities in K39

Using a combination of bound-state spectroscopy and loss spectroscopy, we pinpoint eight intrastate Feshbach resonances in $^{39}$K, as well as six previously unexplored interstate ones. We also perform a detailed characterization of four of the intrastate resonances and two of the interstate ones. We carry out coupled-channel scattering calculations and find good agreement with experiment. The combination of experiment and theory provides a faithful map of the scattering length $a$ and permits precision measurements of the signatures of Efimov physics across four intermediate-strength resonances. We measure the modulation of the $a^4$ scaling of the three-body loss coefficient for both $a<0$ and $a>0$, as well as the many-body loss dynamics at unitarity (where $a$ diverges). The absolute positions of the observed Efimov features confirm a ubiquitous breakdown of Efimov--van-der-Waals universality in $^{39}$K, while their relative positions are in agreement with the universal Efimov ratios. The loss dynamics at the three broadest Feshbach resonances are universal within experimental uncertainties, consistent with observing little variation in the Efimov width parameters.

Quantum degenerate Bose-Fermi atomic gas mixture of 23Na and 40K

We report a compact experimental setup for producing a quantum degenerate mixture of Bose 23Na and Fermi 40K gases. The atoms are collected in dual dark magneto–optical traps (MOT) with species timesharing loading to reduce the light-induced loss, and then further cooled using the gray molasses technique on the D 2 line for 23Na and D 1 line for 40K. The microwave evaporation cooling is used to cool 23Na in | F = 2,mF = 2〉 in an optically plugged magnetic trap, meanwhile, 40K in | F = 9/2,mF = 9/2〉 is sympathetically cooled. Then the mixture is loaded into a large volume optical dipole trap where 23Na atoms are immediately transferred to |1,1〉 for further effective cooling to avoid the strong three-body loss between 23Na atoms in |2,2〉 and 40K atoms in |9/2,9/2〉. At the end of the evaporation in optical trap, a degenerate Fermi gas of 40K with 1.9 × 105 atoms at T/TF = 0.5 in the |9/2,9/2〉 hyperfine state coexists with a Bose–Einstein condensate (BEC) of 23Na with 8 × 104 atoms in the |1,1〉 hyperfine state at 300 nK. We also can produce the two species mixture with the tunable population imbalance by adjusting the 23Na magneto–optical trap loading time.

Stability against three-body clustering in one-dimensional spinless p -wave fermions

We theoretically investigate in-medium two- and three-body correlations in one-dimensional spinless fermions with attractive two-body p-wave interaction. By investigating the variational problem of two- and three-body states above the Fermi sea, we elucidate the fate of the in-medium two- and three-body cluster states. The one-dimensional system with the strong p-wave interaction is found to be stable against the formation of three-body clusters even in the presence of the Fermi sea, in contrast to higher-dimensional systems that suffer the strong three-body loss associated with the trimer formation.

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.

Fluctuation assisted collapses of Bose–Einstein condensates

We study the collapse dynamics of a Bose–Einstein condensate subjected to a sudden change of the scattering length to a negative value by adopting the self-consistent Gaussian state theory for mixed states. Compared to the Gross–Pitaevskii and the Hartree–Fock–Bogoliubov approaches, both fluctuations and three-body loss are properly treated in our theory. We find a new type of collapse assisted by fluctuations that amplify the attractive interaction between atoms. Moreover, the calculation of the fluctuated atoms, the entropy, and the second-order correlation function showed that the collapsed gas significantly deviated from a pure state.

Asymptotic dynamics of certain solutions for an extended nonlinear Gross–Pitaevskii equation with critical nonlinear damping in [formula omitted

Recent experiments have revealed the formation of stable droplets in a dipolar Bose–Einstein condensate (BEC). This surprising result has been explained experimentally by the stabilization provided by the three-body loss process that appears in the form of a critical damping term in an extended Gross–Pitaevskii equation (eGPE) to model the formation of these dipolar quantum droplets. This paper examines the dynamics of solutions to this equation (eGPE). We validate this prediction by proving that nonlinear damping prevents collapse and ensures the existence of global-in-time solutions. The asymptotic dynamics of these solutions are discussed as well, especially when the system is free (without potential). We show that all global solutions asymptotically behave as free waves in time.

Dynamics of dipolar quantum droplets in an extended Gross–Pitaevskii equation in the presence of time-dependent harmonic trapping potential and a damping term

The purpose of this paper is to study the dynamics of solutions to an extended Gross–Pitaevskii equation that models the formation of droplets in a dipolar Bose–Einstein condensate (BEC). The formation of these droplets has been recently discovered by driving the BEC into the strongly dipolar regime. Surprisingly, instead of collapsing, the system formed stable droplets. So far, no rigorous mathematical explanation has been proved. To the best of our knowledge, only experimental results have been obtained. The goal of this paper is to validate this breakthrough discovery. Many predictions/ conjectures properties of these droplets have been stated by some research groups in physics and engineering. In particular, it has been claimed that the stability of these droplets is a consequence of the presence of the damping term in the extended Gross–Pitaevskii equation under study. This term describes the three-body loss process. To accurately model the dynamics of formation of these droplets, it is necessary to consider a time-dependent harmonic trapping potential as well as other terms with different types of nonlinearity among them that describe the Lee–Huang–Yang (LHY). This presents some challenges that will be solved in this paper.

Resonant enhancement of three-body loss between strongly interacting photons

Rydberg polaritons provide an example of a rare type of system where three-body interactions can be as strong or even stronger than two-body interactions. The three-body interactions can be either dispersive or dissipative, with both types possibly giving rise to exotic, strongly-interacting, and topological phases of matter. Despite past theoretical and experimental studies of the regime with dispersive interaction, the dissipative regime is still mostly unexplored. Using a renormalization group technique to solve the three-body Schr\"odinger equation, we show how the shape and strength of dissipative three-body forces can be universally enhanced for Rydberg polaritons. We demonstrate how these interactions relate to the transmission through a single-mode cavity, which can be used as a probe of the three-body physics in current experiments.