Non-Hermitian matter-wave mixing in Bose-Einstein condensates: Dissipation-induced amplification

Wüster, Sebastian; El‐Ganainy, Ramy

doi:10.1103/physreva.96.013605

Cited by 6 publications

(7 citation statements)

References 72 publications

(121 reference statements)

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“…Especially, reference [89] proposed a procedure to produce cold-atom beams with the Lorentzian profile of momentum distribution. And according to reference [90], exploiting the Doppler shift technique, atoms in the spin-↓ state can be velocity-selectively excited to narrow Rydberg or metastable states with a laser, and the following photon recoil could produce a momentum-dependent atomic loss. Denoting the momentum-dependent gain and loss by ±i γΘ p , the system can be readily described by the Hamiltonian (1).…”

Section: Experimental Realizationsmentioning

confidence: 99%

“…In these systems, the gain is usually realized by injecting atoms into the condensate using an atom laser [87], while the loss can be realized by exciting atoms firstly to an excited state with a laser beam and then ejecting them out from the condensate via photon recoil [84]. Due to the momentum distribution of the atom laser [88,89], and the Doppler effect in atom-light interaction [90], gain and loss realized in these ways have a distinct momentum-dependence. Besides, momentum-dependence of gain and loss also occurs in optical mediums, where spatially nonlocal gain and loss after a Fourier transformation are wavevector-dependent [91,92] (since in quantum mechanics, momentum equals Planck constant multiplying wavecector, that is equivalently momentumdependent), and this feature has been proposed to explore the topological physics in photonic system [93].…”

Section: Introductionmentioning

confidence: 99%

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

2022

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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 pseudo spin-1/2 system (in other words, two-state 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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Section: Experimental Realizationsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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

2022

View full text Add to dashboard Cite

show abstract

“…And according to ref. [76], exploiting the Doppler shift technique, atoms in the spin-↓ state can be velocity-selectively excited to narrow Rydberg or metastable states with a laser, and the following photon recoil could produce a momentum-dependent atomic loss. Denoting the momentum-dependent gain and loss by ±i γΘ ( p), the system can be readily described by the Hamiltonian (1).…”

Section: Experimental Realizationsmentioning

confidence: 99%

“…In cold atomic gas systems, the gain can be realized by injecting atoms into the condensate using an atom laser [72], while the loss can be realized by exciting atoms firstly to an excited state with a laser beam and then ejecting them out from the condensate via photon recoil [73]. Due to the momentum-distribution of the atom laser [74,75], and the Doppler effect in atom-light interaction [76], gain and loss realized in these ways have a distinct momentum-dependence. In the optical medium, spatially nonlocal gain and loss after a Fourier transformation are wavevector-dependent (or equivalently "momentum"-dependent) [77,78], and this feature has been proposed to explore the topological physics in photonic systems [79].…”

Section: Introductionmentioning

confidence: 99%

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

Qin,

Zhou,

Dong

2022

Preprint

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Spin-orbital coupling (SOC) and parity-time (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 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 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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“…In the realization of a PT -symmetric BEC system, the atomic gain and loss are usually momentum-dependent, due to the momentum distribution of the atom laser [59,60] and the Doppler effect in atom-light interaction [61]. It is proposed that when the two components of a spin-1/2 atomic BEC are respectively subjected to momentum-dependent balanced gain and loss, a PT -symmetric SOC can be artificially created [62].…”

Section: Introductionmentioning

confidence: 99%

Phonon and maxon instability in Bose–Einstein condensates with parity-time symmetric spin–orbit coupling

Qin,

Zhou,

Dong

2023

New J. Phys.

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Parity-time ( P T ) symmetry has drawn great research interest in non-Hermitian physics. Recently, there is an emerging model of P T -symmetric spin–orbit coupling (SOC) which could be realized with spin-1/2 atomic Bose–Einstein condensates (BECs) when the two spin components are respectively subjected to momentum-dependent gain and loss (Qin et al 2022 New J. Phys. 24 063025). In this model, inter-atom interaction has no influence on the P T -symmetric plane waves. Thus, collective excitation playing the role of fingerprint of inter-atom interaction is investigated in this paper. For the phonon excitation, it is shown that the repulsive interaction between atoms in different spin states, which tends to drive the atoms to populate in only one spin component, can break the P T -symmetry, and leads to a phonon instability. Whereas, for the case of the phonon-maxon-roton collective excitation spectrum, the repulsive interaction between atoms in different spin states can lead to a maxon instability, which does not occur in Hermitian BEC systems (dipolar BECs or BECs with Raman induced SOC). Simulation of the time evolution of the plane wave solution against small noise shows that the maxon instability can result in the formation of a supersolid-like stripe pattern at the initial stage, but the non-Hermitian nature of the system finally destroys the pattern. The phase diagram of stability shows that the Rabi coupling and repulsive interaction between the atoms in the same spin state can stabilize the system.

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Non-Hermitian matter-wave mixing in Bose-Einstein condensates: Dissipation-induced amplification

Cited by 6 publications

References 72 publications

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

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

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

Phonon and maxon instability in Bose–Einstein condensates with parity-time symmetric spin–orbit coupling

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