Dynamics of correlations in a quasi-two-dimensional dipolar Bose gas following a quantum quench

Natu, Stefan S.; Campanello, Leonard; Sarma, S. Das

doi:10.1103/physreva.90.043617

Cited by 18 publications

(30 citation statements)

References 86 publications

(107 reference statements)

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“…In this regime, novel exciting many-body phenomena have been recently observed, as the formation of droplet states stabilised by quantum fluctuations [23][24][25], which may become self-bound [26]. Lanthanide dBECs hence open new roads toward the long-sought observation of roton modes.Prior to this work, dipolar rotons have been mostly connected to pancake-like geometries [3][4][5][6][8][9][10][11][12]. Here, we extend the study of roton physics to the case of a cigar-like geometry with trap elongation along only one direction (y) transverse to the magnetisation axis (z) (Fig.…”

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confidence: 99%

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Observation of roton mode population in a dipolar quantum gas

et al. 2018

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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 4He 1. In quantum liquids, rotons arise from the strong interparticle interactions, whose microscopic description remains debated 2. 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 3. This prospect has raised considerable interest 4–12; 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. Following an interaction quench, the roton mode manifests itself with the appearance of symmetric peaks at well-defined finite 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 13.

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confidence: 99%

“…Prior to this work, dipolar rotons have been mostly connected to pancake-like geometries [3][4][5][6][8][9][10][11][12]. Here, we extend the study of roton physics to the case of a cigar-like geometry with trap elongation along only one direction (y) transverse to the magnetisation axis (z) (Fig.…”

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confidence: 99%

Observation of roton mode population in a dipolar quantum gas

et al. 2018

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“…When long-range interactions are introduced, the dispersion relation corresponding to the quasiparticle spectrum of a BEC is qualitatively different, where the excitation energies of the collective modes depend nonmonotonically on the momentum. Previously BECs with dipole-dipole interactions have been extensively examined [16][17][18][19][20][21][22]. In two-dimensional (2D) dipolar BECs [23], roton and maxon modes emerge, where roton (maxon) modes correspond to local minima (maxima) in the dispersion relation.…”

Section: Introductionmentioning

confidence: 99%

“…Maxon modes, on the other hand, normally appear at lower momentum states [23]. It was shown however that the maxon modes in dipolar BECs are typically unstable and decay rapidly through the Beliaev damping [20,21].…”

Section: Introductionmentioning

confidence: 99%

Dynamical excitation of maxon and roton modes in a Rydberg-dressed Bose-Einstein condensate

McCormack

Nath

2020

Phys. Rev. A

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We investigate the dynamics of a three-dimensional Bose-Einstein condensate of ultracold atomic gases with a soft-core shape 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.

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“…The dispersion curve of such systems is related to a specific k-dependence of an effective interaction potential rather than to strong correlations. Possibility of changing the particles polarization as well as almost free tuning of the short-range interactions combined with the trap geometry modifications enables unprecedented flexibility in the study of the roton spectrum in dipolar gases [20][21][22][23][24][25][26][27][28][29][30][31][32][33][34][35][36][37][38][39] ending with a recent experimental confirmation of the phenomenon [40]. Usually the dipolar system is studied within the Bogoliubov approximation, so that there is no access to the detailed structure of the low-lying excitations.…”

Section: Introductionmentioning

confidence: 99%

Roton in a few-body dipolar system

Ołdziejewski¹,

Górecki²,

Pawłowski³

et al. 2018

New J. Phys.

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We solve numerically exactly the many-body 1D model of bosons interacting via short-range and dipolar forces and moving in the box with periodic boundary conditions. We show that the lowest energy states with fixed total momentum can be smoothly transformed from the typical states of collective character to states resembling single particle excitations. In particular, we identify the celebrated roton state. The smooth transition is realized by simultaneous tuning short-range interactions and adjusting a trap geometry. With our methods we study the weakly interacting regime as well as the regime beyond the range of validity of the Bogoliubov approximation.

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Dynamics of correlations in a quasi-two-dimensional dipolar Bose gas following a quantum quench

Cited by 18 publications

References 86 publications

Observation of roton mode population in a dipolar quantum gas

Observation of roton mode population in a dipolar quantum gas

Dynamical excitation of maxon and roton modes in a Rydberg-dressed Bose-Einstein condensate

Roton in a few-body dipolar system

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