Arxiv Selection May 2020
May 1- May 7 Bhaskar Mukherjee, May 8- May 14 Zehan Li, May 15- May 21 Haiping Hu, May 22- May 28 Sayan Choudhury
May 8
arXiv:2005.03172 [pdf, other]
Skyrmion Ground States of Rapidly Rotating Few-Fermion Systems
Lukas Palm, Fabian Grusdt, Philipp M. Preiss
Comments: 15 pages, 5 figures
Subjects: Quantum Gases (cond-mat.quant-gas)
Abstract. We show that ultracold fermions in an artificial magnetic field open up a new window to the physics of the spinful fractional quantum Hall effect. We numerically study the lowest energy states of strongly interacting few-fermion systems in rapidly rotating optical microtraps. We find that skyrmion-like ground states with locally ferromagnetic, long-range spin textures emerge. To realize such states experimentally, rotating microtraps with higher-order angular momentum components may be used to prepare fermionic particles in a lowest Landau level. We find parameter regimes in which skyrmion-like ground states should be accessible in current experiments and demonstrate an adiabatic pathway for their preparation in a rapidly rotating harmonic trap. The addition of long range interactions will lead to an even richer interplay between spin textures and fractional quantum Hall physics.
May 11
arXiv:2005.03738 [pdf, other]
Ring solitons and soliton sacks in imbalanced fermionic systems
Mats Barkman, Albert Samoilenka, Thomas Winyard, Egor Babaev
Comments: main: 5 pages, 5 figures + supplementary: 4 pages, 1 figure
Subjects: Quantum Gases (cond-mat.quant-gas); Superconductivity (cond-mat.supr-con); Pattern Formation and Solitons (nlin.PS)
We show that in superfluids with fermionic imbalance and uniform ground state, there are solitons representing multiple local minima of the free energy landscape. These solitons have nontrivial soliton-soliton and soliton- vortex interactions and can form complicated bound states in the form of “soliton sacks".
May 12
arXiv:2005.04815 [pdf, other]
Geometrizing quantum dynamics of a Bose-Einstein condensate
Changyuan Lyu, Chenwei Lv, Qi Zhou
Comments: 5 pages, 4 figures
Subjects: Quantum Gases (cond-mat.quant-gas)
Geometry may arise from quantum systems in an unprecedented means such as the gauge the- ory/gravity dual. Whereas emergent geometries often occur in strongly correlated systems, one could ask whether simple quantum systems may also be used to unfold intriguing underlying geometries. Here, we show that quantum dynamics of Bose-Einstein condensates in the weakly interacting regime can be geometrized by a Poincar ́e disk. Each point on such a disk represents a thermofield double state, the fidelity between which equals the metric of this hyperbolic space. Our approach provides us with a unique geometric interpretation of the stable and unstable modes as closed and open trajectories on the Poincar ́e disk, respectively. In particular, the resonant modes, which follow geodesics, naturally equate fundamental quantities including the time, the length, and the temperature. Our work suggests a new geometric framework to coherently control quantum systems, including speeding up, slowing down, and reversing their dynamics using SU(1,1) echoes.
May 13
arXiv:2005.05718 [pdf, other]
Quantized vortices in dipolar supersolid Bose-Einstein condensed gases
A. Gallemì, S. M. Roccuzzo, S. Stringari, A. Recati
Subjects: Quantum Gases (cond-mat.quant-gas)
We investigate the properties of quantized vortices in a dipolar Bose-Einstein condensed gas by means of a generalised Gross-Pitaevskii equation. The size of the vortex core hugely increases by increasing the weight of the dipolar interaction and approaching the transition to the supersolid phase. The critical angular velocity for the existence of an energetically stable vortex decreases in the supersolid, due to the reduced value of the density in the interdroplet region. The angular momentum per particle associated with the vortex line is shown to be smaller than , reflecting the reduction of the global superfluidity. The real-time vortex nucleation in a rotating trap is shown to be triggered, as for a standard condensate, by the softening of the quadrupole mode. For large angular velocities, when the distance between vortices becomes comparable to the interdroplet distance, the vortices are arranged into a honeycomb structure, which coexists with the triangular geometry of the supersolid lattice and persists during the free expansion of the atomic cloud.
May 14
arXiv:2005.06120 [pdf, other]
Few-body physics of one-dimensional ultracold atoms with spin-exchange interaction
Cheng Peng, Xiaoling Cui
Comments: 9 pages with appendix, 3 figures
Subjects: Quantum Gases (cond-mat.quant-gas)
Motivated by recent progresses on ultracold alkaline-earth atoms towards the goal of simulating Kondo physics, in this work we exactly solve the few-body problem of one and two trapped fermions in one dimension interacting with a localized impurity under tunable spin-exchange interaction. It is found that depending on the sign of the spin-exchange coupling, ferromagnetic(FM) or anti- ferromagnetic(AFM), the attractive and repulsive branches can hold different magnetic structures. We demonstrate the Kondo screening effect for the attractive branch of three-body system with the AFM coupling, and show that such screening is absent for the ground state with FM coupling. Moreover, we find a sequence of FM upper branches in the AFM coupling side. These FM states are orthogonal to all other attractive branches and their wave functions feature a full spin-charge separation. The effect of an additional contact interaction and the extension of our results to many particles are also discussed. This work reveals the intriguing physics uniquely associated with the spin-exchange interaction in the few-body point of view, which are promisingly to be explored in the experiment of ultracold alkaline-earth atoms.
