arXiv subjects

Xiaoling Cui

Publications and source records attributed to Xiaoling Cui.

At least 19 recordsLinked to original sources

arXiv2026

Effective scatterings and universal clusters of heteronuclear ultracold mixtures in quasi-low dimensions

We study the effective s-wave scattering of two heteronuclear atoms harmonically confined in quasi-low dimensions, where the atoms have unequal masses and are subject to different confinement frequencies. The resulting effective scattering parameters in low dimensions, including scattering length and effective range, are derived as functions of three-dimensional scattering parameters and confinement strengths. Using realistic Li-K and Li-Cr mixtures as examples, we further compute the binding energies of universal $(1+N)$ clusters in quasi-low dimensions using the effective scattering parameters. Our findings suggest a promising pathway for practically observing universal clusters and their associated many-body phases in low-dimensional ultracold heteronuclear systems.

cond-mat.quant-gas↗

arXiv2026

Quantum fluctuations in a quartet superfluid of two-dimensional Fermi mixture

We study quantum fluctuations in a quartet superfluid (QSF) of two-dimensional (2D) fermion mixtures with mass imbalance. Here QSF is a high-order superfluid that corresponds to the condensation of ($1+3$) clusters, each consisting of a light fermion and three heavy ones. By incorporating the Gaussian fluctuations respecting dominant four-body correlations in this system, our theory successfully recovers the leading universal logarithmic contribution to the 2D equation of state in the deep binding regime, thereby offering a correct physical picture of quartet clusters behaving as composite bosons. By extending the Gaussian fluctuation theory from pairing to quartet superfluids, our results shed light on quantum fluctuations in general fermion superfluids with arbitrarily high-order correlations.

cond-mat.quant-gas↗

arXiv2026

Rabi-coupling-induced three-component quantum droplet in ultracold Bose gases

We uncover a new mechanism for realizing three-component quantum droplets in ultracold Bose gases, where only one inter-species interaction is attractive. In this scheme, the inter-species attraction leads to a self-bound binary droplet, and the third component joins through Rabi coupling with one component of the binary droplet. We find that a stronger Rabi coupling leads to a larger fraction of the third component, but also destabilizes the entire droplet due to the involvement of more repulsive forces. Such instability can be remedied by a finite detuning between the Rabi-coupled components. We demonstrate these results in realistic Na-Rb mixtures, using both thermodynamic analyses and numerical simulations based on extended Gross-Pitaevskii equations. Our work outlines a general route for stabilizing multi-component droplets by bridging an existing binary droplet with additional components via suitable single-particle fields.

cond-mat.quant-gas↗

arXiv2025

Visualizing the dispersions of Fermi polaron and molecule via spin-orbit coupling

We propose to measure the dispersions of Fermi polaron and molecule by engineering spin-orbit coupling (SOC) on the impurity, which induces spin flip with finite momentum transfer. The polaron dispersion can be probed at small SOC momentum from the linear response of impurity spin. For molecule, we show that it can be prepared through an adiabatic steady-state evolution when setting SOC momentum as the Fermi momentum of majority bath. By gradually reducing SOC strength to zero, the steady state smoothly evolves to a molecular state with directional symmetry breaking. The corresponding dispersion can then be probed experimentally through the center-of-mass momentum distribution of molecules at finite density. Our scheme reveals a fundamental momentum difference between Fermi polaron and molecule, thereby offering a clear physical picture for their first-order transition in single-impurity system.

cond-mat.quant-gas↗

arXiv2025

Interaction-induced Dimension Reduction for Bound States in Microwave-Shielded Ultracold Molecules

We investigate tetratomic and hexatomic bound states of ultracold molecules dressed by an elliptic microwave field. We show that these bound states can be accurately described by effective one-dimensional (1D) models incorporating high-order angular fluctuations, despite the physical system is in three-dimensional (3D) free space. By comparing with exact solutions of the full 3D system, we identify the validity region of such 1D description in the parameter plane of ellipticity and coupling strength of microwave field. The hard-core character of these effective models enables a duality between bosonic and fermionic molecules in real and spectral space, while their momentum distributions remain distinct. Our results have demonstrated an effective dimension reduction in microwave-shielded molecular systems, which is purely due to the intrinsic interaction anisotropy rather than any external confinement. Extending to large systems, our results suggest a self-bound single-molecule array as the ground state of both bosonic and fermionic molecular gases.

cond-mat.quant-gas↗

arXiv2025

Generalized Dynamical Duality of Quantum Particles in One Dimension

We prove a generalized dynamical duality for identical particles in one dimension (1D). Namely, 1D systems with arbitrary statistics -- including bosons, fermions and anyons -- approach the same momentum distribution after long-time expansion from a trap, provided they share the same scattering length for short-range interactions. This momentum distribution is uniquely given by the rapidities, or quasi-momenta, of the initial trapped state. Our results can be readily detected in quasi-1D ultracold gases with tunable s- and p-wave interactions.

cond-mat.quant-gas↗

arXiv2025

Chiral Quantum Droplet in a Spin-Orbit Coupled Bose Gas

We report the formation of chiral quantum droplet in a spin-orbit coupled Bose gas, where the system turns to a self-bound droplet when moving towards a particular direction and remains gaseous otherwise. The chirality arises from the breaking of Galilean invariance by spin-orbit coupling, which enables the system to dynamically adjust its condensation momentum and spin polarization in response to its velocity. As a result, only towards a specific moving direction and beyond a critical velocity, the acquired spin polarization can trigger collective interactions sufficient for self-binding and drive a first-order transition from gas to droplet. We have mapped out a phase diagram of droplet, gas and their coexistence for realistic spin-orbit coupled 39K mixtures with tunable moving velocity and magnetic detuning. Our results have revealed the emergence of chirality in spin-orbit coupled quantum gases, which shed light on general chiral phenomena in moving systems with broken Galilean invariance.

cond-mat.quant-gas↗

arXiv2025

Reply to the Comment on "Shell-Shaped Quantum Droplet in a Three-Component Ultracold Bose Gas"

In our Letter (Phys. Rev. Lett. 134, 043402 (2025)), we proposed a self-bound shell-shaped BEC in a three-component ($1,2,3$) Bose gas, where $(2,3)$ and $(1,2)$ droplets are linked as core-shell structure. A recent Comment (Ancilotto, 2505.16554) argued that a ``dimer" configuration should be instead the ground state, where $(2,3)$ and $(1,2)$ stay side-by-side. Moreover, Ancilotto also explored the state formation, finding that a naive trap-release protocol was unable to produce the core-shell structure. In this reply we show that our core-shell structure is an excited state for finite-size systems, while it becomes energetically degenerate with dimer configuration in thermodynamic limit. Furthermore, we find the core-shell structure is locally stable under external perturbations, and if one pays careful attention to mode-matching, a trap-release protocol can well produce this structure.

cond-mat.quant-gas↗

arXiv2025

Universal Bound States with Bose-Fermi Duality in Microwave-Shielded Polar Molecules

We report universal bound states of microwave-shielded ultracold molecules that solely depend on the strengths of long-range dipolar interaction and microwave coupling. Under a highly elliptic microwave field, few-molecule scatterings in three dimension are shown to be governed by effective one-dimensional (1D) models, which well reproduce the tetratomic bound state and the Born-Oppenheimer potential in three-molecule sector. For hexatomic systems comprising three identical molecules, we find much deeper bound state than the tetratomic one, with binding energy exceeding twice of the latter. Strikingly, these bound states display Bose-Fermi duality as facilitated by the effective 1D scattering with a large repulsive core from angular fluctuations. For large molecule ensembles, our results suggest the formation of elongated self-bound droplets with crystalline patterns in both bosonic and fermionic molecules.

cond-mat.quant-gas↗

arXiv2025

Strongly Repulsive 1D Gases at Higher Branches: Spin-Charge Correlation and Coupled Spin-Chain Model

We investigate the higher repulsive branches of one-dimensional (1D) bosonic and fermionic quantum gases beyond the super-Tonks-Girardeau regime, utilizing the Bethe-Ansatz method and exact diagonalization of small trapped clusters. In contrast to the well-studied lowest branches that are characterized by spin-charge separation, we demonstrate the emergence of strong spin-charge correlation in all higher branches with hard-core interactions. This manifests in distinct quasi-momentum distributions and energy spectra for bosons and spin-1/2 fermions, despite their fermionization. Furthermore, trapped fermions in higher branches exhibit novel spin textures, intricately linked to charge excitations, necessitating a coupled multi-chain description beyond single effective spin-chain models. Our findings unveil a rich interplay between spin and charge degrees of freedom in highly excited 1D systems, opening avenues for exploring novel quantum phenomena beyond the conventional paradigm of low-lying states.

cond-mat.quant-gas↗

arXiv2024

Boson-Anyon-Fermion Mapping and Anyon Construction in One Dimension

We establish an exact mapping between identical particles in one dimension with arbitrary exchange statistics, including bosons, anyons and fermions, provided they share the same scattering length. This boson-anyon-fermion mapping facilitates the construction of anyons from a linear superposition of spatially symmetric and anti-symmetric states. This scheme is general and has been demonstrated in a spin-1/2 Fermi gas, where both s- and p-wave bound states can be supported by manipulating spin channels. With a suitable symmetry-breaking field, these bound states are hybridized to form a fractional-wave molecule. The condensation of these molecules in a many-body system leads to anyonic superfluidity, characterized by fractional statistics upon spin exchange within a Cooper pair. These anyonic states can be detected through asymmetric momentum distributions for each spin with a chiral $k^{-3}$ tail. Our results have demonstrated the inadequacy of contact interaction model for anyons in continuum and lattices, and meanwhile proposed a convenient route for engineering fractional phases in the platform of ultracold atoms.

cond-mat.quant-gas↗

arXiv2024

Competing few-body correlations in ultracold Fermi polarons

Polaron, a typical quasi-particle that describes a single impurity dressed with surrounding environment, serves as an ideal platform for bridging few- and many-body physics. In particular, different few-body correlations can compete with each other and lead to many intriguing phenomena. In this work, we review the recent progresses made in understanding few-body correlation effects in attractive Fermi polarons of ultracold gases. By adopting a unified variational ansatz that incorporates different few-body correlations in a single framework, we will discuss their competing effects in Fermi polarons when the impurity and majority fermions have the same or different masses. For the equal-mass case, we review the nature of polaron-molecule transition that is driven by two-body correlations, and especially highlight the finite momentum character and huge degeneracy of molecule states. For the mass-imbalanced case, we focus on the smooth crossover between polaron and various dressed clusters that originate from high-order correlations. These competing few-body correlations reviewed in Fermi polarons suggest a variety of exotic new phases in the corresponding many-body system of Fermi-Fermi mixtures.

cond-mat.quant-gas↗

arXiv2024

Improved Unet brain tumor image segmentation based on GSConv module and ECA attention mechanism

An improved model of medical image segmentation for brain tumor is discussed, which is a deep learning algorithm based on U-Net architecture. Based on the traditional U-Net, we introduce GSConv module and ECA attention mechanism to improve the performance of the model in medical image segmentation tasks. With these improvements, the new U-Net model is able to extract and utilize multi-scale features more efficiently while flexibly focusing on important channels, resulting in significantly improved segmentation results. During the experiment, the improved U-Net model is trained and evaluated systematically. By looking at the loss curves of the training set and the test set, we find that the loss values of both rapidly decline to the lowest point after the eighth epoch, and then gradually converge and stabilize. This shows that our model has good learning ability and generalization ability. In addition, by monitoring the change in the mean intersection ratio (mIoU), we can see that after the 35th epoch, the mIoU gradually approaches 0.8 and remains stable, which further validates the model. Compared with the traditional U-Net, the improved version based on GSConv module and ECA attention mechanism shows obvious advantages in segmentation effect. Especially in the processing of brain tumor image edges, the improved model can provide more accurate segmentation results. This achievement not only improves the accuracy of medical image analysis, but also provides more reliable technical support for clinical diagnosis.

eess.IV↗

arXiv2024

Universal clusters in quasi-two-dimensional ultracold Fermi mixtures

We study universal clusters in quasi-two dimensions (q2D) that consist of a light (L) atom interacting with two or three heavy (H) identical fermions, forming the trimer or tetramer bound state. The axial confinement in q2D is shown to lift the three-fold degeneracy of 3D trimer (tetramer) in $p$-wave channel and uniquely select the ground state with magnetic angular momentum $|m|=1$ ($m=0$). By varying the interaction or confinement strength, we explore the dimensional crossover of these clusters from 3D to 2D, characterized by a gradual change of critical H-L mass ratio for their emergence and momentum-space distribution. Importantly, we find that a finite effective range will {\it not} alter their critical mass ratios in the weak coupling regime. There, we establish an effective 2D model to quantitatively reproduce the properties of q2D clusters, and further identify the optimal interaction strengths for their detections in experiments. Our results suggest a promising prospect for observing universal clusters and associated high-order correlation effects in realistic q2D ultracold Fermi mixtures.

cond-mat.quant-gas↗

arXiv2024

Optimizing Search Advertising Strategies: Integrating Reinforcement Learning with Generalized Second-Price Auctions for Enhanced Ad Ranking and Bidding

This paper explores the integration of strategic optimization methods in search advertising, focusing on ad ranking and bidding mechanisms within E-commerce platforms. By employing a combination of reinforcement learning and evolutionary strategies, we propose a dynamic model that adjusts to varying user interactions and optimizes the balance between advertiser cost, user relevance, and platform revenue. Our results suggest significant improvements in ad placement accuracy and cost efficiency, demonstrating the model's applicability in real-world scenarios.

cs.LG↗

arXiv2023

Shell-Shaped Quantum Droplet in a Three-Component Ultracold Bose Gas

Shell-shaped Bose-Einstein condensate (BEC) is a typical quantum system in curved geometry. Here we propose a new type of shell-shaped BEC with self-bound character, thereby liberating it from stringent conditions such as microgravity or fine-tuned trap. Specifically, we consider a three-component (1,2,3) ultracold Bose gas where (1,2) and (2,3) both form quantum droplets. The two droplets are mutually immiscible due to strong 1-3 repulsion, while still linked by component-2 to form a globally self-bound object. The outer droplet then naturally develops a shell structure without any trapping potential. It is shown that the shell structure can significantly modify the equilibrium density of the core, and lead to unique collective excitations highlighting the core-shell correlation. All results have been demonstrated in a realistic $^{23}$Na-$^{39}$K-$^{41}$K mixture. By extending quantum droplets from flat to curved geometries, this work paves the way for future exploring the interplay of quantum fluctuations and non-trivial real-space topologies in ultracold gases.

cond-mat.quant-gas↗

arXiv2023

Self-bound vortex lattice in a rapidly rotating quantum droplet

A rapidly rotating Bose gas in the quantum Hall limit is usually associated with a melted vortex lattice. In this work, we report a self-bound and visible triangular vortex lattice without melting for a two-dimensional Bose-Bose droplet rotating in the quantum Hall limit, i.e., with rotation frequency $\Omega$ approaching the trapping frequency $\omega$. Increasing $\Omega$ with respect to interaction strength $U$, we find a smooth crossover of the vortex lattice droplet from a needling regime, as featured by small vortex cores and an equilibrium flat-top surface, to the lowest-Landau-level regime with Gaussian-extended cores spreading over the whole surface. The surface density of such a rotating droplet is higher than that of a static one, and their ratio is found to be a universal function of $\Omega/U$. We have demonstrated these results by both numerical and variational methods. The results pave the way for future experimental exploration of rapidly rotating ultracold droplets into the quantum Hall limit.

cond-mat.quant-gas↗

arXiv2023

Quartet Superfluid in Two-dimensional Mass-imbalanced Fermi Mixtures

Quartet superfluid (QSF) is a distinct type of fermion superfluidity that exhibits high-order correlation beyond the conventional BCS pairing paradigm. In this Letter, we report the emergent QSF in 2D mass-imbalanced Fermi mixtures with two-body contact interactions. This is facilitated by the formation of quartet bound state in vacuum that consists of a light atom and three heavy fermions. For an optimized heavy-light number ratio $3:1$, we identify QSF as the ground state in a considerable parameter regime of mass imbalance and 2D coupling strength. Its unique high-order correlation can be manifested in the momentum-space crystallization of pairing field and density distribution of heavy fermions. Our results can be readily detected in Fermi-Fermi mixtures nowadays realized in cold atoms laboratories, and meanwhile shed light on exotic superfluidity in a broad context of mass-imbalanced fermion mixtures.

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