结构相的非共振光机械控制
Nonresonant optomechanical control of structural phases
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中文总结 AI 辅助
本研究将非共振光机械原理应用于硒化锡，通过时域拉曼散射等实验证实其可诱导新结构相形成，为合成隐藏结构相提供了新方向。
中文摘要 AI 辅助
光镊展示了光如何在不吸收的情况下施加力来捕获、排斥和操控微观粒子。近期理论表明，这种力可从粒子操控延伸至驱动固体中的结构相变。本研究将该光机械原理应用于硒化锡（SnSe），该材料因接近多种不同结构相而具备高热电优值，是可切换拓扑晶体绝缘体的候选材料。常规光镊的力源于光场强度梯度，而光机械力由介电常数随声子坐标的梯度介导。与依赖共振激发及通过介电函数虚部吸收的常规方法不同，本方法通过实部色散作用，可直接由拉曼过程驱动，实现选择性跃迁，降低能量成本并具备超快响应。利用时域拉曼散射，研究发现在中红外场强超过临界值时，$A_g$拉曼模式会突然消失且无软化，标志着新结构相的形成。该相与加热或载流子激发诱导的相不同，其光学响应呈现大幅且长寿命的调制。作为补充，研究还通过原子探针层析成像获得了直流场驱动结构相变至更高对称相的证据。本研究验证了非共振光机械相控制的概念，为合成具有独特功能特性的隐藏结构相提供了新机遇。
英文摘要
Optical tweezers demonstrate how light can exert forces to trap, repel, and manipulate microscopic particles without absorption. Recent theory has suggested that such forces can extend beyond particle manipulation to drive structural phase transitions in solids. Here we apply this optomechanical principle to tin selenide (SnSe), a material where proximity to several different structural phases gives rise to its high thermoelectric figure of merit and makes it a candidate for a switchable topological crystalline insulator. Whereas the force for standard optical tweezers arises from a gradient in the intensity of a light field, the optomechanical force is mediated by a gradient in the dielectric constant as a function of phonon coordinate. Unlike conventional methods that rely on resonant excitation and absorption through the imaginary part of the dielectric function, this approach operates dispersively through the real part and can be directly driven by Raman processes, enabling selective transitions with reduced energy cost and ultrafast response. Using time-domain Raman scattering, we show that above a critical mid-infrared field strength the $A_g$ Raman modes disappear abruptly without softening, signaling the formation of a new structural phase. This phase, distinct from those induced by heating or carrier excitation, exhibits large-amplitude and long-lived modulations in its optical response. Complementing this observation, we show also evidence for an equivalent DC-field-driven structural phase transformation to a higher symmetry phase, as observed by atom probe tomography. Our study demonstrates the concept of nonresonant optomechanical phase control and defines novel opportunities for synthesizing hidden structural phases with unique functional properties.
