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標題: | 複雜氧化物之縱波聲學聲子動力學 Longitudinal Acoustic Phonon Dynamics in Complex Oxides |
作者: | Chi-Yuan Yang 楊濟源 |
指導教授: | 張嘉升(Chia-Seng Chang) |
共同指導教授: | 林宮玄(Kung-Hsuan Lin) |
關鍵字: | 鈦酸鍶,釕酸鍶,銥酸鍶,激發探測光譜,超快聲學, strontium titanate,strontium ruthenate,strontium iridate,time-resolved pump-probe spectroscopy,ultrafast acoustics, |
出版年 : | 2020 |
學位: | 博士 |
摘要: | 複雜氧化物為多種元素與氧組成之化合物,其組成相當多元,結構上可以有豐富的變化,也因此在複雜氧化物系統中發現了許多特殊的物理現象,包含:超導性、鐵磁性、鐵電性及光激反應等。透過研究材料聲子特性,可以進而了解新穎現象的產生機制。 本論文建構時間解析激發探測光譜技術,配合先進晶體製成技術,得以透過飛秒雷射產生高頻聲子。選擇複雜氧化物中常見的鈦酸鍶(SrTiO3)當作最先研究的對象且利用具導電性的釕酸鍶(SrRuO3)當作光與聲子的轉換材料。在第一部分中,我們藉由時間尺度布里淵散射研究鈦酸鍶聲子隨溫度變化的行為。變溫範圍涵蓋了105K的鈦酸鍶結構相變溫度,發現吉赫茲(GHz)波段聲子與鈦酸鍶的聲子軟模態有耦合現象。 第二部分,將兩種不同的複雜氧化物製作超晶格,同樣透過脈衝光激發後,可產生兆赫波段聲子且頻率可由改變超晶格的空間周期來調整。由鈦酸鍶(SrTiO3)/釕酸鍶(SrRuO3)堆疊出的的超晶格所產生同調聲子頻率最高,可達約1兆赫(THz)。除了釕酸鍶,另一個備受矚目的材料為銥酸鍶(SrIrO3)同樣具有顯著光致伸縮效應,也因此制備其超晶格樣品與釕酸鍶相比較。此外,我們也展示了同調調控技術,引入另一道控制脈衝光,即可改變同調聲子的強度及相位。研究高頻同調聲子與其衰減時間,對奈米尺度樣品的熱傳導機制可以有更深入的了解。 Complex oxides comprise oxygen and plenty other elements, and display in a variety of structures that lead to exotic phenomena, including superconductivity, ferromagnetism, ferroelectrics, and photo-material interaction. Better understanding of phonon dynamics is a pathway to unveil the mechanisms of novel properties. In this dissertation, time-domain pump-probe spectroscopy is established in order to study hypersound dynamics. Thanks to the advanced technique of crystal fabrication, hypersound in the regime of GHz and THz can be generated by excitation of femtosecond laser. Strontium titanate (SrTiO3, STO) commonly used as a substrate caught our attention. By utilizing metallic strontium ruthenate (SrRuO3, SRO) as the phonon transduce, photo-induced acoustic phonons can probe lattice properties of STO. In the first part, we adopt time-domain Brillouin scattering to investigate temperature dependent phonon dynamics in STO. The variation of temperature covers the STO structural phase transition at 105 K, and we found that the generated GHz acoustic phonon could couple with STO soft mode. In the second part, two different materials are adopted to construct superlattice specimens which is capable of launching hypersound with frequency in THz, and frequency can be tuned by altering the spatial modulation of superlattice. SRO/STO superlattices trigger the phonon with 1 THz. Besides SRO, strontium iridate (SrIrO3, SIO) exhibits more prominent photostriction and is taken as transducer as well for comparison. In the third part, we demonstrate coherent control by introducing an additional control pulse. As a result, the amplitude and phase of coherent phonon can be modified. Investigation on hypersound attenuation offers a different perspective in thermal transport in materials of nanometer scale. |
URI: | http://tdr.lib.ntu.edu.tw/jspui/handle/123456789/8370 |
DOI: | 10.6342/NTU202001996 |
全文授權: | 同意授權(全球公開) |
電子全文公開日期: | 2025-07-28 |
顯示於系所單位: | 物理學系 |
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U0001-2807202020033400.pdf 此日期後於網路公開 2025-07-28 | 5.09 MB | Adobe PDF |
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