近日，韩国延世大学的Keun Su Kim及其研究团队取得一项新进展。经过不懈努力，他们发现具有两对亚晶格量子系统中的电子暗态。相关研究成果已于2024年7月29日在国际知名学术期刊《自然—物理学》上发表。
该研究团队报道了在二硒化钯中发现的一种凝聚态暗态，该系统作为具有两对亚晶格的原始细胞模型。通过角分辨光谱学技术，研究人员发现，在任意光子能量、偏振和散射平面上，整个布里渊区内的价带几乎无法被观测到。研究模型表明，位于半平移位置的两对亚晶格通过多个滑移镜像对称连接，导致它们的相对量子相仅偏振为四种状态，其中三种由于双重相消干涉而呈现暗态。
这一机制对于其他具有两对亚晶格的系统同样适用。研究人员进一步展示了铜酸盐、卤化铅、钙钛矿和密度波系统中观察到的现象如何通过暗态机制来解释。这项研究结果表明，在探究相关现象和光电子特性时，应充分考虑以往被忽视的亚晶格自由度。
据悉，物质的量子态被禁止与光子相互作用，因此无法通过光谱手段检测到，这种状态被称为暗态。这个基本概念可以应用于凝聚态，它表明整个布里渊带的量子态能带是无法探测到的。
附：英文原文
Title: Dark states of electrons in a quantum system with two pairs of sublattices
Author: Chung, Yoonah, Kim, Minsu, Kim, Yeryn, Cha, Seyeong, Park, Joon Woo, Park, Jeehong, Yi, Yeonjin, Song, Dongjoon, Ryu, Jung Hyun, Lee, Kimoon, Kim, Timur K., Cacho, Cephise, Denlinger, Jonathan, Jozwiak, Chris, Rotenberg, Eli, Bostwick, Aaron, Kim, Keun Su
Issue&Volume: 2024-07-29
Abstract: A quantum state of matter that is forbidden to interact with photons and is therefore undetectable by spectroscopic means is called a dark state. This basic concept can be applied to condensed matter where it suggests that a whole band of quantum states could be undetectable across a full Brillouin zone. Here we report the discovery of such condensed-matter dark states in palladium diselenide as a model system that has two pairs of sublattices in the primitive cell. By using angle-resolved photoemission spectroscopy, we find valence bands that are practically unobservable over the whole Brillouin zone at any photon energy, polarization and scattering plane. Our model shows that two pairs of sublattices located at half-translation positions and related by multiple glide-mirror symmetries make their relative quantum phases polarized into only four kinds, three of which become dark due to double destructive interference. This mechanism is generic to other systems with two pairs of sublattices, and we show how the phenomena observed in cuprates, lead halide perovskites and density wave systems can be resolved by the mechanism of dark states. Our results suggest that the sublattice degree of freedom, which has been overlooked so far, should be considered in the study of correlated phenomena and optoelectronic characteristics.
DOI: 10.1038/s41567-024-02586-x
Source: https://www.nature.com/articles/s41567-024-02586-x