Browsing by Subject "Rydberg-dressed bosons"

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Open Access
Collective excitations and density-wave instabilities in one-dimensional soft-core boson systems
(2024-07) Mohammadi, Zohreh
We investigated the dynamics of bosons interacting with Rydberg-dressed potentials in single-wire and double-wire structures. Specifically, we aimed to understand how the addition of Rydberg dressing, with its soft-core nature and van der Waals tail at long distances, influences the behavior of single-wire and doublewire systems of bosons. This investigation was conducted using the random phase approximation (RPA) and the Bogoliubov-de Gennes (BdG) mean-field approximation at zero temperature, focusing on the emergence of collective modes and density-wave instabilities. We examined the dispersions of collective modes in single-wire and double-wire structures of bosons with Rydberg-dressed interactions. In the long-wavelength limit, symmetric and anti-symmetric modes show linear behavior in wave vectors with distinct sound velocities. A prominent maxon-roton feature appears at intermediate wave vectors, especially at large coupling constants. The influence of wire spacing on mode dispersion is significant: smaller spacings lead to the disappearance of the asymmetric mode with free-particle-like dispersion, while larger spacings result in mode degeneracy in symmetric bi-wires due to diminished inter-wire coupling. The system becomes unstable toward density-waves at strong couplings, indicated by the vanishing roton energy, affecting both symmetric and antiymmetric branches. Additionally, density imbalances between wires shift the energy of the excitation branches and destabilize the homogeneous superfluid phase at lower coupling constants. While the roton softening observed suggests instability toward densitymodulated phases, more sophisticated numerical methods are needed to characterize these phases accurately.
Open Access
Density and pseudo-spin rotons in a bilayer of soft-core bosons
(Institute of Physics, 2023-05-26) Pouresmaeeli, F.; Abedinpour, S. H.; Tanatar, Bilal
We study the dynamics of a bilayer system of bosons with repulsive soft-core Rydberg-dressed interactions within the mean-field Bogoliubov-de Gennes approximation. We find roton minima in both symmetric and asymmetric collective density modes of the symmetric bilayer. Depending on the density of bosons in each layer and the spacing between two layers, the homogeneous superfluid phase becomes unstable in either (or both) of these two channels, leading to density and pseudo-spin-density wave instabilities in the system. Breaking the symmetry between two layers, either with a finite counterflow or a density imbalance renormalizes the dispersion of collective modes and makes the system more susceptible to density-wave instability.