Polarons and bipolarons in a two-dimensional square lattice

被引:8
|
作者
Ding, Shanshan [1 ]
Dominguez-Castro, G. A. [2 ,3 ]
Julku, Aleksi [1 ]
Camacho-Guardian, Arturo [2 ]
Bruun, Georg M. [1 ,4 ,5 ]
机构
[1] Aarhus Univ, Ctr Complex Quantum Syst, Dept Phys & Astron, DK-8000 Aarhus, Denmark
[2] Univ Nacl Autonoma Mexico, Inst Fis, Apartado Postal 20-364, Mexico City 01000, Mexico
[3] Leibniz Univ Hannover, Inst Theoret Phys, Appelstr 2, D-30167 Hannover, Germany
[4] Southern Univ Sci & Technol, Shenzhen Inst Quantum Sci & Engn, Shenzhen 518055, Peoples R China
[5] Southern Univ Sci & Technol, Dept Phys, Shenzhen 518055, Peoples R China
来源
SCIPOST PHYSICS | 2023年 / 14卷 / 06期
关键词
QUANTUM SIMULATIONS; PHYSICS; ATOMS;
D O I
10.21468/SciPostPhys.14.6.143
中图分类号
O4 [物理学];
学科分类号
0702 ;
摘要
Quasiparticles and their interactions are a key part of our understanding of quantum many-body systems. Quantum simulation experiments with cold atoms have in recent years advanced our understanding of isolated quasiparticles, but so far they have pro-vided limited information regarding their interactions and possible bound states. Here, we show how exploring mobile impurities immersed in a Bose-Einstein condensate (BEC) in a two-dimensional lattice can address this problem. First, the spectral properties of individual impurities are examined, and in addition to the attractive and repulsive po-larons known from continuum gases, we identify a new kind of quasiparticle stable for repulsive boson-impurity interactions. The spatial properties of polarons are calculated showing that there is an increased density of bosons at the site of the impurity both for repulsive and attractive interactions. We then derive an effective Schrodinger equation describing two polarons interacting via the exchange of density oscillations in the BEC, which takes into account strong impurity-boson two-body correlations. Using this, we show that the attractive nature of the effective interaction between two polarons com-bined with the two-dimensionality of the lattice leads to the formation of bound states - i.e. bipolarons. The wave functions of the bipolarons are examined showing that the ground state is symmetric under particle exchange and therefore relevant for bosonic impurities, whereas the first excited state is doubly degenerate and odd under particle exchange making it relevant for fermionic impurities. Our results show that quantum gas microscopy in optical lattices is a promising platform to explore the spatial properties of polarons as well as to finally observe the elusive bipolarons.
引用
收藏
页数:26
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