以飛秒光譜探測系統研究鐵酸鉍(001)薄膜的超快動力學行為

Abstract

多鐵材料為同時表現出鐵電性質和磁性有序，此種材料具有不尋常的物理特性。鐵酸鉍為常溫的磁電多鐵材料，因此這種材料的應用以及物理特性十分重要。在本論文中，我們與朱英豪老師的團隊合作，請他們提供我們良好的鐵酸鉍薄膜。D. S. Rana的團隊在超快雷射產生THz的實驗中觀測到超快去極化的現象，並且認為此現象為電子與晶格間的交互作用。因此利用超快激發-探測光譜量測不同溫度下材料的瞬時反射率變化ΔR/R隨著時間延遲變化的情形，藉此我們可以觀察材料中電子、晶格與自旋的超快動力行為，並且了解多鐵材料複雜的物理機制，並且可以觀測到超快去極化的現象。

Multiferroic materials, which show simultaneous ferroelectric and magnetic ordering, exhibit unusual physical properties. Bismuth ferrite is a room temperature magnetoelectric multiferroic material. Therefore its applications and physical properties are very important. In this thesis, we cooperate with Professor Y. H. Chu’s group. We requested them to provide good bismuth ferrite films. D. S. Rana’s group in the experiment, which is THz emission by ultrafast laser, observe phenomenon of ultrafast depolarization, and they consider the phenomenon is about electron-lattice interaction. Using ultrafast pump-probe spectroscopy, we measure the transient reflectivity change ΔR/R of the material as a function of a pump-probe delay at various temperatures. We can observe the ultrafast dynamic behaviors of electron, lattice and spin, and we can understand complex physical mechanism in this material. And we can observe the phenomenon of ultrafast depolarization.