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Ground states of a Bose-Einstein Condensate in a one-dimensional laser-assisted optical lattice

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ABSTRACT

We study the ground-state behavior of a Bose-Einstein Condensate (BEC) in a Raman-laser-assisted one-dimensional (1D) optical lattice potential forming a multilayer system. We find that, such system can be described by an effective model with spin-orbit coupling (SOC) of pseudospin (N-1)/2, where N is the number of layers. Due to the intricate interplay between atomic interactions, SOC and laser-assisted tunnelings, the ground-state phase diagrams generally consist of three phases–a stripe, a plane wave and a normal phase with zero-momentum, touching at a quantum tricritical point. More important, even though the single-particle states only minimize at zero-momentum for odd N, the many-body ground states may still develop finite momenta. The underlying mechanisms are elucidated. Our results provide an alternative way to realize an effective spin-orbit coupling of Bose gas with the Raman-laser-assisted optical lattice, and would also be beneficial to the studies on SOC effects in spinor Bose systems with large spin.

No MeSH data available.


The ground state momentum km/λ (a,b) and interlayer polarization 〈Fz〉 (c,d) as functions of tunneling J/Eλ for given interactions g2D/Eλ = 0.05 (left panel) and g2D/Eλ = 0.2 (right panel) at N = 2. SP, PW and NP denote Stripe, Plane Wave and Normal phases, respectively.
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f4: The ground state momentum km/λ (a,b) and interlayer polarization 〈Fz〉 (c,d) as functions of tunneling J/Eλ for given interactions g2D/Eλ = 0.05 (left panel) and g2D/Eλ = 0.2 (right panel) at N = 2. SP, PW and NP denote Stripe, Plane Wave and Normal phases, respectively.

Mentions: In the dilute limit (g2D/Eλ ≪ 1), above a critical tunneling strength, i.e. J > Jc1 ≃ 0.5Eλ, the system is in the zero-momentum Normal phase. While for J < Jc2 ≃ 0.41Eλ, a Stripe phase is favored. Between them (Jc1 < J < Jc2), a Plane Wave phase is expected to have lower energy. The regime of such Plane Wave phase gets diminished with increasing of interaction g2D, and finally disappears at a tricritical point around (J/Eλ, g2D/Eλ) ≃ (0.38, 0.11), where three phases merge. Beyond the tricritical point, only Normal to Stripe phase transition survives (See Fig. (4b,d)). These features essentially reflect the competitions between kinetic and interaction energies of these states. In the weak interaction regime, the kinetic energy is dominant, and the system is always in a Normal phase when the single particle spectrum has only one minimum at k = 0. On the double minima side, the kinetic energies of Stripe and Plane Wave phases for the same km are degenerate, and would be further lifted by the atomic interactions.


Ground states of a Bose-Einstein Condensate in a one-dimensional laser-assisted optical lattice
The ground state momentum km/λ (a,b) and interlayer polarization 〈Fz〉 (c,d) as functions of tunneling J/Eλ for given interactions g2D/Eλ = 0.05 (left panel) and g2D/Eλ = 0.2 (right panel) at N = 2. SP, PW and NP denote Stripe, Plane Wave and Normal phases, respectively.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC5121596&req=5

f4: The ground state momentum km/λ (a,b) and interlayer polarization 〈Fz〉 (c,d) as functions of tunneling J/Eλ for given interactions g2D/Eλ = 0.05 (left panel) and g2D/Eλ = 0.2 (right panel) at N = 2. SP, PW and NP denote Stripe, Plane Wave and Normal phases, respectively.
Mentions: In the dilute limit (g2D/Eλ ≪ 1), above a critical tunneling strength, i.e. J > Jc1 ≃ 0.5Eλ, the system is in the zero-momentum Normal phase. While for J < Jc2 ≃ 0.41Eλ, a Stripe phase is favored. Between them (Jc1 < J < Jc2), a Plane Wave phase is expected to have lower energy. The regime of such Plane Wave phase gets diminished with increasing of interaction g2D, and finally disappears at a tricritical point around (J/Eλ, g2D/Eλ) ≃ (0.38, 0.11), where three phases merge. Beyond the tricritical point, only Normal to Stripe phase transition survives (See Fig. (4b,d)). These features essentially reflect the competitions between kinetic and interaction energies of these states. In the weak interaction regime, the kinetic energy is dominant, and the system is always in a Normal phase when the single particle spectrum has only one minimum at k = 0. On the double minima side, the kinetic energies of Stripe and Plane Wave phases for the same km are degenerate, and would be further lifted by the atomic interactions.

View Article: PubMed Central - PubMed

ABSTRACT

We study the ground-state behavior of a Bose-Einstein Condensate (BEC) in a Raman-laser-assisted one-dimensional (1D) optical lattice potential forming a multilayer system. We find that, such system can be described by an effective model with spin-orbit coupling (SOC) of pseudospin (N-1)/2, where N is the number of layers. Due to the intricate interplay between atomic interactions, SOC and laser-assisted tunnelings, the ground-state phase diagrams generally consist of three phases&ndash;a stripe, a plane wave and a normal phase with zero-momentum, touching at a quantum tricritical point. More important, even though the single-particle states only minimize at zero-momentum for odd N, the many-body ground states may still develop finite momenta. The underlying mechanisms are elucidated. Our results provide an alternative way to realize an effective spin-orbit coupling of Bose gas with the Raman-laser-assisted optical lattice, and would also be beneficial to the studies on SOC effects in spinor Bose systems with large spin.

No MeSH data available.