三維無序金屬之非彈性電子散射時間及量子傳輸現象之研究

Abstract

電子在無序系統中的傳輸性質，在凝態物理是一重要課題。在低溫下，三維弱無序系統( )中，實驗及理論一致認為電子非彈性散射機制是以電子-聲子散射為主。但非彈性電子-聲子散射率卻未有一致的結論。根據Belitz-Wysokinsk理論，隨無序度增加，在三維接近金屬-絕緣體轉變的強無序系統，非彈性散射將以電子-電子散射為主。我們以熱蒸鍍方式製作一系列從強無序到弱無序的ScAg和ScAu三維合金樣品，試圖連接兩區域，探討電子非彈性散射機制的轉變。 在這一系列的ScAg和ScAu三維合金樣品中，我們控制良導體Ag和Au的摻雜量，來改變電阻率，達到無序度的改變。而磁電阻的量測與弱局域磁電阻函數的分析，可讓我們得到電子非彈性散射率 。實驗結果是隨無序度減少(Ag或Au含量的增加)，自旋-軌域散射率增加，我們發現電子非彈性散射率將會由 轉變成 ，表示電子非彈性散射機制由電子-電子散射為主漸轉變成電子-聲子散射為主。 另外我們量測一系列的TiGeSc和ScZr合金的電阻對溫度關係數據，探討因無序而增強的電子-電子交互作用。兩組的樣品的數據大致上均符合電子-電子交互作用對電阻的修正。

The quantum transport of disordered electronic systems is a very important topic in condensed matter physics. In three-dimensional weakly disordered conductors ( ), both theoretical and experimental studies have found that electron-phonon scattering is the sole, dominant inelastic scattering process at low temperature. However, the electron-phonon scattering rate is not clear. According to Belitz-Wysokinsk theory, while the system is three-dimensional strong-disordered conductors near mobility edge, electron-electron scattering is dominant inelastic scattering process, causing .In this work, we performed transport measurements in a series of three-dimension at ScAg and ScAu samples spanning from strongly to weakly disordered regime to study the evolution of inelastic scattering mechanisms. In this ScAg and ScAu alloy samples, the degree of disorder can be controlled by adjusting the doping concentration of Ag or Au. We can extract the inelastic electron scattering rate from the measurements of magnetoresistivities and analysis of weakly-localization magnetoresistivity function. We observed that the inelastic electron scattering rate would have transition from to with decreasing degree of disorder (increasing doping concentration of the Ag or Au). This result establishes a crossover of the inelastic electron dephasing from electron-electron scattering to electron-phonon scattering. In addition, we have fabricated a series TiGeSc and ScZr alloy samples. By measuring R(T) at low temperature, we have studied the disordered-enhanced electron-electron interaction. The data confirms the prediction of disordered-enhanced electron-electron interaction theory.