The Experts below are selected from a list of 696 Experts worldwide ranked by ideXlab platform
Ludwig Mathey - One of the best experts on this subject based on the ideXlab platform.
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Exotic roton excitations in quadrupolar Bose–Einstein condensates
New Journal of Physics, 2015Co-Authors: Martin Lahrz, Mikhail Lemeshko, Ludwig MatheyAbstract:We investigate the occurrence of Rotons in a quadrupolar Bose–Einstein condensate confined to two dimensions. Depending on the particle density, the ratio of the contact and quadrupole–quadrupole interactions, and the alignment of the quadrupole moments with respect to the confinement plane, the dispersion relation features two or four point-like roton minima or one ring-shaped minimum. We map out the entire parameter space of the roton behavior and identify the instability regions. We propose to observe the exotic Rotons by monitoring the characteristic density wave dynamics resulting from a short local perturbation, and discuss the possibilities to detect the predicted effects in state-of-the-art experiments with ultracold homonuclear molecules.
Rejish Nath - One of the best experts on this subject based on the ideXlab platform.
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Dynamical excitation of maxon and roton modes in a Rydberg-dressed Bose-Einstein condensate
Physical Review A, 2020Co-Authors: Gary Mccormack, Rejish NathAbstract:We investigate the dynamics of a three-dimensional Bose-Einstein condensate of ultracold atomic gases with a soft-core-shaped long-range interaction, which is induced by laser dressing the atoms to a highly excited Rydberg state. For a homogeneous condensate, the long-range interaction drastically alters the dispersion relation of the excitation, supporting both roton and maxon modes. Rotons are typically responsible for the creation of supersolids, while maxons are normally dynamically unstable in BECs with dipolar interactions. We show that maxon modes in the Rydberg-dressed condensate, on the contrary, are dynamically stable. We find that the maxon modes can be excited through an interaction quench, i.e., turning on the soft-core interaction instantaneously. The emergence of the maxon modes is accompanied by oscillations at high frequencies in the quantum depletion, while Rotons lead to much slower oscillations. The dynamically stable excitation of the roton and maxon modes leads to persistent oscillations in the quantum depletion. Through a self-consistent Bogoliubov approach, we identify the dependence of the maxon mode on the soft-core interaction. Our study shows that maxon and roton modes can be excited dynamically and simultaneously by quenching Rydberg-dressed long-range interactions. This is relevant to current studies in creating and probing exotic states of matter with ultracold atomic gases.
Martin Lahrz - One of the best experts on this subject based on the ideXlab platform.
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Exotic roton excitations in quadrupolar Bose–Einstein condensates
New Journal of Physics, 2015Co-Authors: Martin Lahrz, Mikhail Lemeshko, Ludwig MatheyAbstract:We investigate the occurrence of Rotons in a quadrupolar Bose–Einstein condensate confined to two dimensions. Depending on the particle density, the ratio of the contact and quadrupole–quadrupole interactions, and the alignment of the quadrupole moments with respect to the confinement plane, the dispersion relation features two or four point-like roton minima or one ring-shaped minimum. We map out the entire parameter space of the roton behavior and identify the instability regions. We propose to observe the exotic Rotons by monitoring the characteristic density wave dynamics resulting from a short local perturbation, and discuss the possibilities to detect the predicted effects in state-of-the-art experiments with ultracold homonuclear molecules.
Gary Mccormack - One of the best experts on this subject based on the ideXlab platform.
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Dynamical excitation of maxon and roton modes in a Rydberg-dressed Bose-Einstein condensate
Physical Review A, 2020Co-Authors: Gary Mccormack, Rejish NathAbstract:We investigate the dynamics of a three-dimensional Bose-Einstein condensate of ultracold atomic gases with a soft-core-shaped long-range interaction, which is induced by laser dressing the atoms to a highly excited Rydberg state. For a homogeneous condensate, the long-range interaction drastically alters the dispersion relation of the excitation, supporting both roton and maxon modes. Rotons are typically responsible for the creation of supersolids, while maxons are normally dynamically unstable in BECs with dipolar interactions. We show that maxon modes in the Rydberg-dressed condensate, on the contrary, are dynamically stable. We find that the maxon modes can be excited through an interaction quench, i.e., turning on the soft-core interaction instantaneously. The emergence of the maxon modes is accompanied by oscillations at high frequencies in the quantum depletion, while Rotons lead to much slower oscillations. The dynamically stable excitation of the roton and maxon modes leads to persistent oscillations in the quantum depletion. Through a self-consistent Bogoliubov approach, we identify the dependence of the maxon mode on the soft-core interaction. Our study shows that maxon and roton modes can be excited dynamically and simultaneously by quenching Rydberg-dressed long-range interactions. This is relevant to current studies in creating and probing exotic states of matter with ultracold atomic gases.
Francesca Ferlaino - One of the best experts on this subject based on the ideXlab platform.
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Observation of Roton Mode Population in a Dipolar Quantum Gas
Nature physics, 2018Co-Authors: Lauriane Chomaz, Rick Van Bijnen, D. Petter, Giulia Faraoni, Simon Baier, J. H. Becher, Manfred J. Mark, Falk Waechtler, Luis Santos, Francesca FerlainoAbstract:The concept of a roton, a special kind of elementary excitation, forming a minimum of energy at finite momentum, has been essential to understand the properties of superfluid $^4$He. In quantum liquids, Rotons arise from the strong interparticle interactions, whose microscopic description remains debated. In the realm of highly-controllable quantum gases, a roton mode has been predicted to emerge due to magnetic dipole-dipole interactions despite of their weakly-interacting character. This prospect has raised considerable interest; yet roton modes in dipolar quantum gases have remained elusive to observations. Here we report experimental and theoretical studies of the momentum distribution in Bose-Einstein condensates of highly-magnetic erbium atoms, revealing the existence of the long-sought roton mode. By quenching the interactions, we observe the roton appearance of peaks at well-defined momentum. The roton momentum follows the predicted geometrical scaling with the inverse of the confinement length along the magnetisation axis. From the growth of the roton population, we probe the roton softening of the excitation spectrum in time and extract the corresponding imaginary roton gap. Our results provide a further step in the quest towards supersolidity in dipolar quantum gases.
