Photoinduced phase transitions in matters have gained tremendous attention over the past few years. However, their ultrashort lifetime makes their study and possible control very challenging. Here, we report on highly anisotropic d-d excitonic excitations yielding photoinduced metal-insulator transitions (MITs) in quasi-one-dimensional metals Sr_1-yNbO_x using Mueller-Matrix spectroscopic ellipsometry, transient ultraviolet Raman spectroscopy, transient mid-infrared reflectivity and angular-resolved photoemission spectroscopy supported with density functional theory. Interestingly, the MITs are driven by photo-pumping of d-d excitons, causing the metallic a-axis to become insulating while the insulating b- and c-axis concomitantly become a correlated metal. We assign these effects to an interplay between the melting of charge and lattice orderings along the different anisotropic optical axes and Bose-Einstein-like condensation of the photoinduced excitons. The long lifetime in the order of several seconds of the metastable MITs gives greater flexibility to study and manipulate the transient excitonic state for potential applications in exciton-based optoelectronic devices.

在过去的几年中，物质中的光诱导相变已经引起了极大的关注。但是，它们的超短寿命使他们的研究和可能的控制变得非常困难。在这里，我们报道了使用Mueller-Matrix光谱椭偏仪，瞬态紫外拉曼光谱，瞬态中红外反射率和准一维金属Sr _{1- y} NbO _x产生光诱导金属-绝缘体跃迁（MITs）的高度各向异性dd激子激发。密度泛函理论支持的角分辨光发射光谱。有趣的是，MIT的通过的光泵浦从动d - d激子，从而导致金属一轴变为绝缘，同时绝缘b轴和c轴同时成为相关金属。我们将这些效应分配给沿不同各向异性光轴的电荷熔化和晶格有序之间的相互作用，以及光诱导激子的玻色-爱因斯坦样凝聚。亚稳态MIT的几秒钟的长寿命为研究和操纵瞬态激子态提供了更大的灵活性，以用于基于激子的光电器件中的潜在应用。