Stoica V A, Laanait N, Dai C, Hong Z, Yuan Y, Zhang Z, Lei S, McCarter M R, Yadav A, Damodaran A R, Das S, Stone G A, Karapetrova J, Walko D A, Zhang X, Martin L W, Ramesh R, Chen L-Q, Wen H, Gopalan V, Freeland J W
Department of Materials Science and Engineering, Pennsylvania State University, University Park, PA, USA.
Center for Nanophase Materials Sciences, Oak Ridge, TN, USA.
Nat Mater. 2019 Apr;18(4):377-383. doi: 10.1038/s41563-019-0311-x. Epub 2019 Mar 18.
Stimulation with ultrafast light pulses can realize and manipulate states of matter with emergent structural, electronic and magnetic phenomena. However, these non-equilibrium phases are often transient and the challenge is to stabilize them as persistent states. Here, we show that atomic-scale PbTiO/SrTiO superlattices, counterpoising strain and polarization states in alternate layers, are converted by sub-picosecond optical pulses to a supercrystal phase. This phase persists indefinitely under ambient conditions, has not been created via equilibrium routes, and can be erased by heating. X-ray scattering and microscopy show this unusual phase consists of a coherent three-dimensional structure with polar, strain and charge-ordering periodicities of up to 30 nm. By adjusting only dielectric properties, the phase-field model describes this emergent phase as a photo-induced charge-stabilized supercrystal formed from a two-phase equilibrium state. Our results demonstrate opportunities for light-activated pathways to thermally inaccessible and emergent metastable states.
用超快光脉冲进行刺激可以实现并操控具有新兴结构、电子和磁现象的物质状态。然而，这些非平衡相通常是瞬态的，挑战在于将它们稳定为持久状态。在此，我们表明，在交替层中平衡应变和极化状态的原子尺度的PbTiO₃/SrTiO₃超晶格，通过亚皮秒光脉冲被转换为一种超晶相。该相在环境条件下无限期持续存在，并非通过平衡途径形成，并且可以通过加热消除。X射线散射和显微镜显示，这种不寻常的相由具有高达30纳米的极性、应变和电荷有序周期性的相干三维结构组成。通过仅调整介电特性，相场模型将这种新兴相描述为由两相平衡态形成的光诱导电荷稳定超晶。我们的结果展示了通向热不可及和新兴亚稳态的光激活途径的机会。
