Data from : Emergence of tunable periodic density correlations in a Floquet-Bloch system

In quantum gases, two-body interactions are responsible for a variety of instabilities that depend on the characteristics of both trapping and interactions. These instabilities can lead to the appearance of new structures or patterns. We report on the Floquet engineering of such a parametric instability, on a Bose-Einstein condensate held in a time-modulated optical lattice. The modulation triggers a destabilization of the condensate into a state exhibiting a density modulation with a new spatial periodicity. This new crystal-like order, which shares characteristic correlation properties with a supersolid, directly depends on the modulation parameters: the interplay between the Floquet spectrum and interactions generates narrow and adjustable instability regions, leading to the growth, from quantum or thermal fluctuations, of modes with a density modulation non commensurate with the lattice spacing. This study demonstrates the production of metastable exotic states of matter through Floquet engineering, and paves the way for further studies of dissipation in the resulting phase, and of similar phenomena in other geometries.在量子气体中，两体相互作用会引发多种不稳定性，这类不稳定性同时取决于囚禁条件与相互作用的特性。这些不稳定性可催生全新的结构或物相图案。我们报道了针对此类参量不稳定性（parametric instability）的弗洛凯工程（Floquet engineering）研究，实验对象为囚禁于时调光学晶格（time-modulated optical lattice）中的玻色-爱因斯坦凝聚体（Bose-Einstein condensate）。该周期性调制会触发凝聚体失稳，使其演化为呈现新型空间周期密度调制的物态。这种类晶体有序结构与超固体（supersolid）具有共通的关联特性，其形成直接依赖于调制参数：弗洛凯谱（Floquet spectrum）与相互作用之间的协同作用会产生窄幅且可调的不稳定性区域，使得源自量子涨落或热涨落的、空间周期与晶格间距不匹配的密度调制模式得以生长。本研究证明了通过弗洛凯工程可制备亚稳奇异物质态，同时为后续研究该衍生物相中的耗散现象，以及其他几何构型下的同类现象铺平了道路。