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A dynamical symmetry triad in high-harmonic generation revealed by attosecond recollision control
摘要： A key element of optical spectroscopy is the link between observable selection rules and the underlying symmetries of an investigated physical system. Typically, selection rules arise from the interaction of its constituents. In light-matter interaction, emergent phenomena are particularly prominent in strongly driven states of matter, as evident in light-induced variants of superconductivity, the Hall effect, and topological insulators in the condensed phase, as well as exceptional points in molecules, Kramers–Henneberger states in gases, and time-crystals in isolated many-body systems. Such emergent states are often governed by novel symmetry properties and topologies, which may be probed by external or emitted radiation fields. Here, we report on the experimental observation of an emergent class of symmetries in the electromagnetic field emitted by a strongly driven atomic system. Specifically, we analyze the sets of allowed and forbidden harmonic orders in high-harmonic generation from tailored bi-circular and bi-elliptical fields. Corroborated by theoretical modeling, the identified selection rules correspond to a complete triad of dynamical symmetries. We believe that the general principles underlying our observations will be equally relevant for other systems, including crystalline solids.
关键词： bi-elliptical fields,optical spectroscopy,high-harmonic generation,dynamical symmetries,selection rules,bi-circular fields,symmetries
更新于2025-09-19 17:13:59
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[IEEE 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - Munich, Germany (2019.6.23-2019.6.27)] 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - Multi-Scale Symmetries and Selection Rules in High Harmonic Generation
摘要： Symmetry-based analysis is very useful in many fields of science. In the case of time-dependent systems, the symmetries of interest are dynamical, and are maintained during the system’s evolution in time. Interestingly, such symmetries may manifest over several length scales, e.g. both microscopically and macroscopically. For example, in high harmonic generation (HHG), micro-scale dynamical symmetries (DSs) yield selection rules that forbid some harmonic orders and determine the polarizations of the allowed harmonics [1], as was formulated recently in a consistent group theory [2]. Macroscopically, DSs of the wave equation may induce selection rules with respect to phase-matching conditions and conservation of angular or linear momentum [3]. However, the DSs of these different length scales are generally thought to be non-interacting, and have so far only been described separately. Here we formulate and explore plethora of multi-scale dynamical symmetries (MSDS), where the symmetry operations involve both microscopic and macroscopic length scales. We derive all possible MSDS operations and their resulting selection rules in HHG, and experimentally demonstrate non-trivial selection rules of the new theory.
关键词： selection rules,dynamical symmetries,high harmonic generation,multi-scale dynamical symmetries,symmetry-based analysis
更新于2025-09-11 14:15:04