複雜自適應物質研究---子計四：超快光譜技術應用於複雜自適應物質之物理特性之研究

Abstract

複雜自適應物質的詭異物理行為，近年來已引起凝態物理界的廣泛興 趣和研究熱潮。在本三年計畫中，我們將延續前面幾年有關利用超快光譜 技術量測高溫超導體物理特性的經驗，繼續研究一些複雜自適應物質中的 強關聯電子材料薄膜(包含鈣鈦礦超導薄膜、鈉鈷氧薄膜、鈣鈦礦磁性薄 膜、鐵磁多鐵薄膜、和其他鐵電薄膜等)、半導體薄膜和光電聚合物薄膜等 的超快光學動力學，以瞭解這些材料的基本物理特性。 使用的超快光譜量測系統除了已建立的時間解析光激發-光檢測系 統、兆赫波時域光譜量測系統外，本計畫擬建立時間解析光激發-兆赫波檢 測系統。在時間解析的激發-探測研究方面，我們將研究上述樣品的超快弛 緩行為，包含電子與聲子作用、載子弛緩行為、超導能隙與虛能隙的弛緩 行為、電子自旋、電荷和軌道弛緩行為等。 在赫波時域光譜量測研究方面，可得到樣品在兆赫波頻域內的介電特 性，包含複數折射率、介電函數和導電率等的頻譜分佈。理論上，在兆赫 波時域光譜量測系統的入射光路徑中，加一分光鏡、延遲移動平台和反射 鏡等，引導光至樣品，即可建立時析光激發-兆赫波探測量測系統。樣品受 光激發時，則可得到其實部和虛部導電率的瞬時變化率，利用此導電率動 態行為隨溫度和頻率的變化關係，可探討這些材料的基本物理特性。

The emergent behaviors of the complex adaptive materials have been extensively studied in modern condensed matter physics recently. In this three-year project, we shall extend our experience in studying the physical properties of high Tc superconductors by ultrafast laser spectroscopy to investigate the ultrafast dynamics of complex adaptive matter (including strongly correalated electron materials: high-Tc superconductors, NaxCoO2:yH2O, colossal-magnetoresistance manganites, multiferroic, ferroelectric thin films etc), semicoductors and electrooptic polymers, which have been developed in our deparment. In addition to the time-resolved optical pump-optical probe (OPOP) and THz time domain spectroscopy (THz TDS) measurement systems, which have been built in our laboratory, we shall build a time-resolved optical pump-THz probe (OPTP) measurement system in this project. In the case of OPOP experiments, the ultrafast dynamics, such as electron-phonon interaction, relaxation dynamics of carriers, superconducting gap (pseudogap), spin, charge, and orbital ordering of the samples will be investigated. In the case of THz TDS experiments, the measured results provide the direct information on the dielectric properties of the sample in the THz range, including the complex index of refraction, dielectric function, and conductivity. In principle, the THz TDS system can be extended to OPTP system simply. All that is required is the addition of a beam splitter, a mechanical delay line and a mirror in the optical path to guide the optical pulses to the sample.With the optical excitation, the measured results reveal the dynamics of dielectric properties of the sample, and the changes in the conductivity can be obtained directly. The physical properties of these materials then can be investigated from the temperature and frequency dependence of the conductivity dynamics.