Measurable signatures and preparation of bosonic fractional Chern insulators in optical lattices with ultracold atoms
报告人：王波涛 博士后(布鲁塞尔自由大学)
邀请人：李朝红 教授
时 间：2024年07月11日（周四）10:30-12:00
地 点：深大粤海校区光电所 313会议室
报告摘要：
十几年来，冷原子实验在实现拓扑能带方面取得了长足的进展，这为在光晶格超冷原子系统中研究强关联拓扑物态奠定了基础，同时也将其带到了国际研究前沿。通过结合目前的量子气体显微镜技术，我们详细研究了填充数为1/2的分数量子霍尔态的实现条件。基于密度矩阵重整化群的数值方法，我们考察了利用静态在位束缚势和动态调控局域磁通两种方法来制备分数拓扑激发，并给出了实验观测的理想参数区间 [1]。考虑到有效地制备拓扑物态是对其进行研究的先决条件，我们最近提出了“冷原子升降机”这一量子态制备方案 [2]。基于目前成熟的箱势阱调控技术，我们考虑将整个系统分为目标系统和库两个部分。通过适当地调节库的势能大小，原子将被输运到目标系统中从而形成包括手征性边界态和分数陈绝缘体在内的新奇量子物态。与此同时，该方案还可以用来去除系统中的激发从而将目标系统冷却到拓扑基态。我们的工作为利用超冷原子系统制备和研究强关联拓扑物态提供了新的思路。
Recent progress in engineering topological band structures in optical lattice systems makes it promising to study fractional Chern insulators with ultracold atoms. Here we consider a realistic finite system of a few repulsively interacting bosons on a square lattice with magnetic flux and sharp edges, as it can be realized in quantum-gas microscopes. We investigate under which conditions a fractional Chern insulator state corresponding to the Laughlin-like state at filling \nu=1/2 can be stabilized. Using numerical simulations, we also find clear signatures of excitations with fractional charge in response both to static pinning potentials and dynamical flux insertion. Since the compressible edges, which are found to feature chiral currents, can serve as a reservoir, these observations are robust against various system parameters [1]. Meanwhile, we introduce a new way to prepare an topological states of matter, which is based on dynamically tuning box potentials in a sub-box configuration [2]. The scheme, dubbed "cold-atom elevator", consists in preparing a quantum gas in a box-shaped trap, specifically partitioned so as to connect a system of interest to adjustable atomic reservoirs. By properly lifting the elevator, atoms gently leave the reservoirs, hence building up the target quantum many-body state inside the quantum simulator. Moreover, this setting naturally incorporates a vacuum-cleaning scheme that effectively cools down the prepared quantum state, by repeatedly removing hot particles from the system in a highly-controllable manner. The prime assets of the cold-atom elevator lie in its practical simplicity and universality, which are expected to bring the quantum simulation of strongly-correlated quantum matter to a new level.
[1] Botao Wang , Xiaoyu Dong, and André Eckardt, Measurable signatures of bosonic fractional Chern insulator states and their fractional excitations in a quantum gas microscope, SciPost Phys. 12, 095 (2022).
[2] Botao Wang, Monika Aidelsburger, Jean Dalibard, André Eckardt, and Nathan Goldman, The cold-atom elevator: From edge-state injection to the preparation of fractional Chern insulators, Phys. Rev. Lett. 132, 163402 (2024).
报告人简介:
王波涛博士来自布鲁塞尔自由大学，目前在Nathan Goldman 教授课题组从事博士后研究。博士期间，王波涛师从André Eckardt教授，就读于德国马克思普朗克复杂系统物理研究所和柏林工业大学，并以优异成绩毕业 (summa cum laude)。王波涛共发表学术论文7篇（其中2篇Physical Review Letter为一作兼共同通讯作者），并参与撰写中文参考书1部（科学出版社）。其研究兴趣主要集中于冷原子中的人工规范场、拓扑物态的量子模拟、量子态的制备以及量子气体的动力学性质等。
Botao Wang is doing his postdoc in the group of Nathan Goldman at Université Libre de Bruxelles (ULB), Brussels. He did his PhD with André Eckardt at Max Planck Institute for the Physics of Complex Systems and Technische Universität Berlin, Germany. His main research topics include Floquet engineering and artificial gauge fields, topology in cold atoms, and dynamical properties of quantum gases.
欢迎各位老师和同学参加!
