arXiv subjects

Jieli Qin

Publications and source records attributed to Jieli Qin.

14 recordsLinked to original sources

arXiv2025

From elastic to inelastic deformation of a dipolar supersolid

Due to its peculiar superfluid-crystal duality feature, supersolid has received great research interest. Recently, researchers have paid much attention to its elastic response properties; however, the inelastic deformation has barely been explored. In this work, we study the transition from elastic to inelastic deformation of a dipolar supersolid Bose-Einstein condensate trapped in a box potential (i.e., a dipolar supersolid with finite size). We obtained the stationary supersolid states (both ground and excited) of the system, and examined the relation between the supersolid size and the number of unit cells it can accommodate, which can essentially help us to understand the dynamical responses of the supersolid during a dilation or compression process. We found that within a certain dilation or compression extent, the supersolid can retain its original crystal structure, that is, it endures an elastic deformation; however, when the extent exceeds a critical threshold, the original crystal structure of the supersolid will be disrupted, which signifies an inelastic deformation. Furthermore, we both analytically and numerically determined the critical point of the transition from elastic to inelastic deformation, and mapped out a phase diagram. These results open up new territory in the research of supersolid mechanical properties, and may find applications in quantum material science and quantum-based technologies.

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arXiv2025

Bi-Josephson Effect in a Driven-Dissipative Supersolid

The Josephson effect is a macroscopic quantum tunneling phenomenon in a system with superfluid property, when it is split into two parts by a barrier. Here, we examine the Josephson effect in a driven-dissipative supersolid realized by coupling Bose-Einstein condensates to an optical ring cavity. We show that the spontaneous breaking of spatial translation symmetry in supersolid makes the location of the splitting barrier have a significant influence on the Josephson effect. Remarkably, for the same splitting barrier, depending on its location, two different types of DC Josephson currents are found in the supersolid phase (compared to only one type found in the superfluid phase). Thus, we term it a bi-Josephson effect. We examine the Josephson relationships and critical Josephson currents in detail, revealing that the emergence of supersolid order affects these two types of DC Josephson currents differently -- one is enhanced, while the other is suppressed. The findings of this work unveil unique Josephson physics in the supersolid phase, and show new opportunities to build novel Josephson devices with supersolids.

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arXiv2023

Bright solitons in a spin-orbit-coupled dipolar Bose-Einstein condensate trapped within a double-lattice

By effectively controlling the dipole-dipole interaction, we investigate the characteristics of the ground state of bright solitons in a spin-orbit coupled dipolar Bose-Einstein condensate. The dipolar atoms are trapped within a double-lattice which consists of a linear and a nonlinear lattice. We derive the motion equations of the different spin components, taking the controlling mechanisms of the diolpe-dipole interaction into account. An analytical expression of dipole-dipole interaction is derived. By adjusting the dipole polarization angle, the dipole interaction can be adjusted from attraction to repulsion. On this basis, we study the generation and manipulation of the bright solitons using both the analytical variational method and numerical imaginary time evolution. The stability of the bright solitons is also analyzed and we map out the stability phase diagram. By adjusting the long-range dipole-dipole interaction, one can achieve manipulation of bright solitons in all aspects, including the existence, width, nodes, and stability. Considering the complexity of our system, our results will have enormous potential applications in quantum simulation of complex systems.

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arXiv2022

Supersolid Gap Soliton in a Bose-Einstein Condensate and Optical Ring Cavity coupling system

The system of a transversely pumped Bose-Einstein condensate (BEC) coupled to a lossy ring cavity can favor a supersolid steady state. Here we find the existence of supersolid gap soliton in such a driven-dissipative system. By numerically solving the mean-field atom-cavity field coupling equations, gap solitons of a few different families have been identified. Their dynamical properties, including stability, propagation and soliton collision, are also studied. Due to the feedback atom-intracavity field interaction, these supersolid gap solitons show numerous new features compared with the usual BEC gap solitons in static optical lattices.

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arXiv2022

Imaginary spin-orbital coupling in parity-time symmetric systems with momentum-dependent gain and loss

Spin-orbital coupling (SOC) and parity-time ($\mathcal{PT}$) symmetry both have attracted paramount research interest in condensed matter physics, cold atom physics, optics and acoustics to develop spintronics, quantum computation, precise sensors and novel functionalities. Natural SOC is an intrinsic relativistic effect. However, there is an increasing interest in synthesized SOC nowadays. Here, we show that in a $\mathcal{PT}$-symmetric spin-1/2 system, the momentum-dependent balanced gain and loss can synthesize a new type of SOC, which we call imaginary SOC. The imaginary SOC can substantially change the energy spectrum of the system. Firstly, we show that it can generate a pure real energy spectrum with a double-valleys structure. Therefore, it has the ability to generate supersolid stripe states. Especially, the imaginary SOC stripe state can have a high contrast of one. Moreover, the imaginary SOC can also generate a spectrum with tunable complex energy band, in which the waves are either amplifying or decaying. Thus, the imaginary SOC would also find applications in the engineering of $\mathcal{PT}$-symmetry-based coherent wave amplifiers/absorbers. Potential experimental realizations of imaginary SOC are proposed in cold atomic gases and systems of coupled waveguides constituted of nonlocal gain and loss.

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arXiv2021

Collision of two self-trapped atomic matter wave packets in an optical ring cavity

The interaction between atomic Bose-Einstein condensate (BEC) and light field in an optical ring cavity gives rise to many interesting phenomena such as supersolid and movable self-trapped matter wave packets. Here we examined the collision of two self-trapped atomic matter wave packets in an optical ring cavity, and abundant colliding phenomena have been found in the system. Depending on the magnitude of colliding velocity, the collision dynamics exhibit very different features compared with the cavity-free case. When the initial colliding velocities of the two wave packets are small, they correlatedly oscillate around their initial equilibrium positions with a small amplitude. Increasing the collision velocity leads to severe scattering of the BEC atoms; after the collision, the two self-trapped wave packets usually break into small pieces. Interestingly, we found that such a medium velocity collision is of great phase sensitivity, which may make the system useful in precision matter wave interferometry. When the colliding velocity is further increased, in the bad cavity limit, the two wave packets collide phenomenally similar to two classical particles -- they firstly approach each other, then separate with their shape virtually maintained. However, beyond the bad cavity limit, they experience severe spatial spreading.

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arXiv2020

Self-trapped atomic matter wave in a ring cavity

We studied a system of atomic Bose-Einstein condensate coupled to a ring cavity within the mean-field theory. Due to the interaction between atoms and light field, the atoms can be self-trapped. This is verified with both variational and numerical methods. We examined the stability of these self-trapped states. For a weakly pumped cavity, they spread during the evolution; while at strong pumping, they can maintain the shape for a long time. We also studied the moving dynamics of these self-trapped waves, and found out that it can be strongly affected by the cavity decay rate. For a small cavity decay rate, the self-trapped waves undergo a damped oscillation. Increasing the cavity decay rate will lead to a deceleration of the self-trapped waves. We also compared the main results with the semiclassical theory in which atoms are treated as classical particles.

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arXiv2020

Unidirectional spin transport of a spin-orbit-coupled atomic matter wave using a moving Dirac $δ$-potential well

We study the transport of a spin-orbit-coupled atomic matter wave using a moving Dirac $δ$-potential well. In a spin-orbit-coupled system, bound states can be formed in both ground and excited energy levels with a Dirac $δ$ potential. Because Galilean invariance is broken in a spin-orbit-coupled system, moving of the potential will induce a velocity-dependent effective detuning. This induced detuning breaks the spin symmetry and makes the ground-state transporting channel be spin-$\uparrow$ ($\downarrow$) favored while makes the excited-state transporting channel be spin-$\downarrow$ ($\uparrow$) favored for a positive-direction (negative-direction) transporting. When the $δ$-potential well moves at a small velocity, both the ground-state and the excited-state channels contribute to the transportation, and thus both the spin components can be efficiently transported. However, when the moving velocity of the $δ$-potential well exceeds a critical value, the induced detuning is large enough to eliminate the excited bound state, and makes the ground bound state the only transporting channel, in which only the spin-$\uparrow$ ($\downarrow$) component can be efficiently transported in a positive (negative) direction. This work demonstrates a prototype of unidirectional spin transport.

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arXiv2020

Bound states of spin-orbit coupled cold atoms in a Dirac delta-function potential

Dirac delta-function potential is widely studied in quantum mechanics because it usually can be exactly solved and at the same time is useful in modeling various physical systems. Here we study a system of delta-potential trapped spinorbit coupled cold atoms. The spin-orbit coupled atomic matter wave has two kinds of evanescent modes, one of which has pure imaginary wavevector and is an ordinary evanescent wave; while the other with a complex number wave vector is recognized as oscillating evanescent wave. We identified the eigenenergy spectra and the existence of bound states in this system. The bound states can be constructed analytically using the two kinds of evanescent modes and we found that they exhibit typical features of stripe phase, separated phase or zero-momentum phase. In addition to that, the properties of semi-bound states are also discussed, which is a localized wave packet on a plane wave background.

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arXiv2019

Non-spreading matter-wave packets in a ring

Non-spreading wave packets and matter-wave packets in ring traps both have attracted great research interests due to their miraculous physical properties and tempting applications for quite a long time. Here, we proved that there exists only one set of non-spreading matter-wave packets in a free ring, and this set of wave packets have been found analytically. These non-spreading matter-wave packets can be realized in a toroidal trapped Bose-Einstein condensate system with the help of Feshbach resonance to eliminate contact interaction between atoms. Since experimentally residual interaction noise will always exist, its effect on the stability of these non-spreading wave packets is also examined. Qualitatively, under weak residual interaction noise, these non-spreading wave packets can preserve their shape for quite a long time, while a stronger interaction noise will induce shape breathing of the wave packets. Shape-keeping abilities of these wave packets are further studied quantitatively. We found that this set of wave packets have the same shape-keeping ability against interaction noise. And, the shape-keeping ability is linearly related to the interaction noise strength.

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arXiv2019

Effect of spin-orbit coupling on tunnelling escape of Bose-Einstein condensate

We theoretically investigate quantum tunnelling escape of a spin-orbit (SO) coupled Bose-Einstein condensate (BEC) from a trapping well. The condensate is initially prepared in a quasi-one-dimensional harmonic trap. Depending on the system parameters, the ground state can fall in different phases --- single minimum, separated or stripe. Then, suddenly the trapping well is opened at one side. The subsequent dynamics of the condensate is studied by solving nonlinear Schrödinger equations. We found that the diverse phases will greatly change the tunneling escape behavior of SO coupled BECs. In single minimum and separated phases, the condensate escapes the trapping well continuously, while in stripe phase it escapes the well as an array of pulses. We also found that SO coupling has a suppressing effect on the tunnelling escape of atoms. Especially, for BECs without inter-atom interaction, the tunnelling escape can be almost completely eliminated when the system is tuned near the transition point between single minimum and stripe phase. Our work thus suggests that SO coupling may be a useful tool to control the tunnelling dynamic of BECs, and potentially be applied in realization of atom lasers and matter wave switches.

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arXiv2019

Tail-free self-accelerating solitons and vortices

Self-accelerating waves in conservative systems, which usually feature slowly decaying tails, such as Airy waves, have drawn great interest in studies of quantum and classical wave dynamics. They typically appear in linear media, while nonlinearities tend to deform and eventually destroy them. We demonstrate, by means of analytical and numerical methods, the existence of robust one- and two-dimensional (1D and 2D) self-accelerating tailless solitons and solitary vortices in a model of two-component Bose-Einstein condensates, dressed by a microwave (MW) field, whose magnetic component mediates long-range interaction between the matter-wave constituents, with the feedback of the matter waves on the MW field taken into account. In particular, self-accelerating 2D solitons may move along a curved trajectory in the coordinate plane. The system may also include the spin-orbit coupling between the components, leading to similar results for the self-acceleration. The effect persists if the contact cubic nonlinearity is included. A similar mechanism may generate 1D and 2D self-accelerating solitons in optical media with thermal nonlinearity.

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arXiv2016

Stable giant vortex annuli in microwave-coupled atomic condensates

Stable self-trapped vortex annuli (VAs) with large values of topological charge S (giant VAs) are not only a subject of fundamental interest, but are also sought for various applications, such as quantum information processing and storage. However, in conventional atomic Bose-Einstein condensates (BECs) VAs with S>1 are unstable. Here, we demonstrate that robust self-trapped fundamental solitons (with S=0) and bright VAs (with the stability checked up to S=5), can be created in the free space by means of the local-field effect (the feedback of the BEC on the propagation of electromagnetic waves) in a condensate of two-level atoms coupled by a microwave (MW) field, as well as in a gas of MW-coupled fermions with spin 1/2. The fundamental solitons and VAs remain stable in the presence of an arbitrarily strong repulsive contact interaction (in that case, the solitons are constructed analytically by means of the Thomas-Fermi approximation). Under the action of the moderate attractive contact interaction which, by itself, would lead to collapse, the fundamental solitons and VAs exist and are stable, respectively; it is interesting that higher-order VAs are more robust than their lower-order couterparts, on the contrary to what is known in other systems that may support stable self-trapped vortices. Conditions for the experimental realizations of the VAs are discussed.

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arXiv2015

Hybrid matter-wave-microwave solitons produced by the local-field effect

It was recently found that the electric local-field effect (LFE) can lead to strong coupling of atomic Bose-Einstein condensates (BECs) to off-resonant optical fields. We demonstrate that the magnetic LFE gives rise to a previously unexplored mechanism for coupling a (pseudo) spinor BEC or fermion gas to microwaves (MWs). We present a theory for the magnetic LFE, and find that it gives rise to a short-range attractive interaction between two components of the (pseudo) spinor, and a long-range interaction between them. The latter interaction, resulting from deformation of the magnetic field, is locally repulsive but globally attractive, in sharp contrast with its counterpart for the optical LFE, produced by phase modulation of the electric field. Our analytical results, confirmed by the numerical computations, show that the long-range interaction gives rise to modulational instability of the spatially uniform state, and creates stable ground states in the form of hybrid matter-wave-microwave solitons (which seem like one-dimensional magnetic monopoles), with a size much smaller than the MW wavelength, even in the presence of arbitrarily strong contact inter-component repulsion. The setting is somewhat similar to exciton-polaritonic condensates in semiconductor microcavities. The release of matter waves from the soliton may be used for the realization of an atom laser. The analysis also applies to molecular BECs with rotational states coupled by the electric MW field.

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