近日，西班牙巴塞罗那科技学院的Jens Biegert及其研究团队取得一项新进展。经过不懈努力，他们揭示具有一个拓扑光场的块状二硫化钼中的谷电子学。相关研究成果已于2024年4月24日在国际权威学术期刊《自然》上发表。
该研究团队利用块状二硫化钼（一种在谷处没有贝里曲率的中心对称材料）实现了对谷偏振的全光学和非谐振控制。研究人员运用了一种通用方法，即通过自旋角动量形状的三叶草光控制脉冲来切换材料的电子拓扑，并通过简单的相位旋转瞬时破坏了时空反演对称性，从而诱导了谷极化。研究人员使用了非共线光学探针脉冲的二次谐波瞬态产生技术，该技术能够依赖于三叶草相位旋转来确认谷偏振的状态。研究表明，对谷自由度的直接光学控制并不局限于单层结构。
事实上，这种控制对于具有任意层数的系统和块状材料是可能的。这种非共振谷控制具有通用性，并且速度达到了光速，这为在量子相干时间尺度上工作的工程高效多材料谷电子器件的开发提供了可能。此外，他们开发的光学方法不仅可以设置和读取块状过渡金属二硫族半导体的谷极化电子状态，还具有潜在的实用价值，可应用于量子相干时间尺度的数字存储和量子计算等领域。
据悉，材料中电子的谷自由度不仅为节能信息存储开辟了新的途径，更为量子信息处理提供了诱人的前景。然而，当前利用谷偏振所面临的挑战在于，需要单层结构或特定材料工程来满足对称条件，同时需要避免能量耗散的非谐振光学控制，并具备以光速切换谷偏振的能力。
附：英文原文
Title: Valleytronics in bulk MoS2 with a topologic optical field
Author: Tyulnev, Igor, Jimnez-Galn, lvaro, Poborska, Julita, Vamos, Lenard, Russell, Philip St. J., Tani, Francesco, Smirnova, Olga, Ivanov, Misha, Silva, Rui E. F., Biegert, Jens
Issue&Volume: 2024-04-24
Abstract: The valley degree of freedom of electrons in materials promises routes towards energy-efficient information storage with enticing prospects for quantum information processing. Current challenges in utilizing valley polarization are symmetry conditions that require monolayer structures or specific material engineering, non-resonant optical control to avoid energy dissipation and the ability to switch valley polarization at optical speed. We demonstrate all-optical and non-resonant control over valley polarization using bulk MoS2, a centrosymmetric material without Berry curvature at the valleys. Our universal method utilizes spin angular momentum-shaped trefoil optical control pulses to switch the material’s electronic topology and induce valley polarization by transiently breaking time and space inversion symmetry through a simple phase rotation. We confirm valley polarization through the transient generation of the second harmonic of a non-collinear optical probe pulse, depending on the trefoil phase rotation. The investigation shows that direct optical control over the valley degree of freedom is not limited to monolayer structures. Indeed, such control is possible for systems with an arbitrary number of layers and for bulk materials. Non-resonant valley control is universal and, at optical speeds, unlocks the possibility of engineering efficient multimaterial valleytronic devices operating on quantum coherent timescales. We develop an optical method that can set and read the state of electrons in the valley polarization of bulk transition metal dichalcogenide semiconductors, with potential utility as digital storage at quantum coherent timescales and application in quantum computing.
DOI: 10.1038/s41586-024-07156-y
