| 1. |
- Bengtsson, J., et al.
(författare)
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Quantum Szilard Engine with Attractively Interacting Bosons
- 2018
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Ingår i: Physical Review Letters. - 0031-9007. ; 120:10
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Tidskriftsartikel (refereegranskat)abstract
- We show that a quantum Szilard engine containing many bosons with attractive interactions enhances the conversion between information and work. Using an ab initio approach to the full quantum-mechanical many-body problem, we find that the average work output increases significantly for a larger number of bosons. The highest overshoot occurs at a finite temperature, demonstrating how thermal and quantum effects conspire to enhance the conversion between information and work. The predicted effects occur over a broad range of interaction strengths and temperatures.
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| 2. |
- Bengtsson, J., et al.
(författare)
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Bosonic Szilard engine assisted by Feshbach resonances
- 2018
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Ingår i: Physical Review A. - 2469-9926. ; 97:6
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Tidskriftsartikel (refereegranskat)abstract
- It was recently found that the information-to-work conversion in a quantum Szilard engine can be increased by using a working medium of bosons with attractive interactions. In the original scheme, the work output depends on the insertion and removal position of an impenetrable barrier that acts like a piston, separating the chambers of the engine. Here, we show that the barrier removal process can be made fully reversible, resulting in a full information-to-work conversion if we also allow for the interaction strength to change during the cycle. Hence, it becomes possible to reach the maximum work output per cycle dictated by the second law of thermodynamics. These findings can be experimentally verified, for instance, with ultracold atoms as a working medium, where a change of interaction strength can be controlled by Feshbach resonances.
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| 3. |
- Mukherjee, K., et al.
(författare)
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Supersolid stacks in antidipolar Bose-Einstein condensates
- 2023
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Ingår i: Physical Review A. - 2469-9926. ; 108:2
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Tidskriftsartikel (refereegranskat)abstract
- We theoretically investigate a supersolid structure taking the form of stacked, disk-shaped superfluid droplets connected via a dilute superfluid, in an antidipolar condensate. A phase diagram is determined for varying the particle number and scattering length, identifying the regions of a regular dipolar superfluid, supersolid stacks, and isolated stacked disk-shaped droplets in an experimentally realizable trapping potential. The collective Bogoliubov excitation spectrum across the superfluid-supersolid phase transition is studied, and the transition point is found to be associated with the breaking of the degeneracy of the two lowest-lying modes. The dynamical generation of the supersolid stacks is also investigated by ramping down the scattering length across the phase transition. Moreover, we have studied the impact of vortex-line penetration on the phase transition. We have found that the presence of a vortex line causes the supersolid region to move towards weaker contact interactions. Our detailed numerical simulations highlight that an antidipolar condensate can create such supersolid stacks within an experimentally reachable parameter regime.
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| 4. |
- Nilsson Tengstrand, M., et al.
(författare)
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Rotating Binary Bose-Einstein Condensates and Vortex Clusters in Quantum Droplets
- 2019
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Ingår i: Physical Review Letters. - 0031-9007. ; 123:16
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Tidskriftsartikel (refereegranskat)abstract
- Quantum droplets may form out of a gaseous Bose-Einstein condensate, stabilized by quantum fluctuations beyond mean field. Determining the ground state of a rotating binary condensate, we show that multiple singly quantized vortices may form in these droplets at moderate angular momenta in two dimensions. Droplets carrying these precursors of an Abrikosov lattice remain self-bound for certain timescales after switching off an initial harmonic confinement. Intriguingly, we find evidence of a metastable persistent current in these new types of binary condensates. We discuss how this finding can be used to experimentally generate vortex-carrying quantum droplets.
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| 5. |
- Nilsson Tengstrand, M., et al.
(författare)
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Toroidal dipolar supersolid with a rotating weak link
- 2023
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Ingår i: Physical Review A. - 2469-9926. ; 107:6
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Tidskriftsartikel (refereegranskat)abstract
- Ring-shaped superfluids with weak links provide a perfect environment for studying persistent currents and dynamic stirring protocols. Here, we investigate the effects of a weak-link system on dipolar supersolids. By calculating the ground-state energy at fixed angular momenta, we find that metastable persistent currents may exist in the supersolid phase near the superfluid transition point. When stirring the weak link rapidly enough, we show that vortices can enter the supersolid. These vortex entries cause phase slips, emitting solitonic excitations that interfere with the crystalline structure of the supersolid, leading to a continuous melting and recrystallization of the droplets. Finally, we examine the release of vortex-carrying supersolids from the trap, observing that the released density exhibits a discrete structure associated with the density modulation and a central hole resulting from the vortex core.
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| 6. |
- Stürmer, P., et al.
(författare)
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Breathing mode in two-dimensional binary self-bound Bose-gas droplets
- 2021
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Ingår i: Physical Review A. - 2469-9926. ; 103:5
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Tidskriftsartikel (refereegranskat)abstract
- In this work, we study the stationary structures and the breathing mode behavior of a two-dimensional self-bound binary Bose droplet. We employ an analytical approach using a variational ansatz with a super-Gaussian trial order parameter and compare it with the numerical solutions of the extended Gross-Pitaevskii equation. We find that the super-Gaussian is superior to the often used Gaussian ansatz in describing the stationary and dynamical properties of the system. For sufficiently large nonrotating droplets the breathing mode is energetically favorable compared to the self-evaporating process. However, for small self-bound systems our results differ based on the ansatz. Inducing angular momentum by imprinting multiply quantized vortices at the droplet center, this preference for the breathing mode persists independent of the norm.
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| 7. |
- Stürmer, P., et al.
(författare)
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Mixed bubbles in a one-dimensional Bose-Bose mixture
- 2022
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Ingår i: Physical Review Research. - 2643-1564. ; 4:4
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Tidskriftsartikel (refereegranskat)abstract
- We investigate a Bose-Bose mixture across the miscible-immiscible phase transition governed by quantum fluctuations in one dimension. We find the recently predicted so-called mixed bubbles as ground states close to the mean-field miscible-immiscible threshold. These bubbles form a pocket of miscibility, separated by one of the components. The collective excitations reflect the symmetry breaking resulting from the bubble formation. The partial miscibility of the system allows for persistent currents in an annular confinement. Intriguingly, the mixed bubble acts like an intrinsic weak link, connecting the rotational behavior of the mixed bubble state to current efforts in atomtronic applications.
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| 8. |
- Tengstrand, M. Nilsson, et al.
(författare)
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Droplet-superfluid compounds in binary bosonic mixtures
- 2022
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Ingår i: Physical Review A. - 2469-9926. ; 105:3
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Tidskriftsartikel (refereegranskat)abstract
- While quantum fluctuations in binary mixtures of bosonic atoms with short-range interactions can lead to the formation of a self-bound droplet, for equal intracomponent interactions but an unequal number of atoms in the two components, there is an excess part that cannot bind to the droplet. Imposing confinement, as here through periodic boundary conditions in a one-dimensional setting, the droplet becomes amalgamated with a residual condensate. The rotational properties of this compound system reveal simultaneous rigid-body and superfluid behavior in the ground state and uncover that the residual condensate can carry angular momentum even in the absence of vorticity. In contradiction to the intuitive idea that the superfluid fraction of the system would be entirely made up of the excess atoms not bound by the droplet, we find evidence that this fraction is higher than what one would expect in such a picture. Our findings are corroborated by an analysis of the elementary excitations in the system, and shed new light on the coexistence of localization and superfluidity.
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| 9. |
- Nilsson Tengstrand, Mikael, et al.
(författare)
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Persistent Currents in Toroidal Dipolar Supersolids
- 2021
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Ingår i: Physical Review A. - 2469-9926. ; 103
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Tidskriftsartikel (refereegranskat)abstract
- We investigate the rotational properties of a dipolar Bose-Einstein condensate trapped in a toroidal geometry. Studying the ground states in the rotating frame and at fixed angular momenta, we observe that the condensate acts in distinctly different ways depending on whether it is in the superfluid or in the supersolid phase. We find that intriguingly, the toroidal dipolar condensate can support a supersolid persistent current which occurs at a local minimum in the ground state energy as a function of angular momentum, where the state has a vortex solution in the superfluid component of the condensate. The decay of this state is prevented by a barrier that in part consists of states where a fraction of the condensate mimics solid-body rotation in a direction opposite to that of the vortex. Furthermore, the rotating toroidal supersolid shows hysteretic behavior that is qualitatively different depending on the superfluid fraction of the condensate.
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| 10. |
- Sachdeva, Rashi, et al.
(författare)
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Self-bound supersolid stripe phase in binary Bose-Einstein condensates
- 2020
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Ingår i: Physical Review A. - 2469-9926. ; 102
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Tidskriftsartikel (refereegranskat)abstract
- Supersolidity—a coexistence of superfluidity and crystalline or amorphous density variations—has been vividly debated ever since its conjecture. While the initial focus was on helium-4, recent experiments uncovered supersolidity in ultracold dipolar quantum gases. Here we propose a self-bound supersolid phase in a binary mixture of Bose gases with short-range interactions, making use of the nontrivial properties of spin-orbit coupling. We find that a first-order phase transition from a self-bound supersolid stripe phase to a zero-minimum droplet state of the Bose gas occurs as a function of the Rabi coupling strength. These phases are characterized using the momentum distribution, the transverse spin polarization, and the superfluid fraction. The critical point of the transition is estimated in an analytical framework. The predicted density-modulated supersolid stripe and zero-minimum droplet phase should be experimentally observable in a binary mixture of 39K with spin-orbit coupling.
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