許多研究指出電荷密度波通常發生於低維度材料，因其擁有特殊異向的晶體結構和電子能帶結構。電荷密度波主要是由於電荷密度週期性的分佈，導致費米面能隙的形成，又由於較強的電子-聲子交互作用，造成系統因交互作用能量的不同而可能產生不同的基態 (絕緣體或半導體)，以及不同的物理特性。
本研究針對稀土碲化物RTe3 (R = Tb, Er) 系列樣品，於10 K至400 K區間進行電阻率(𝜌)、熱導率(κ)、熱電勢(S)與比熱(CP)之量測。比較不同稀土離子半徑對CDW相變之影響。電阻率顯示TbTe3與ErTe3在高溫處皆有金屬性轉半導體性行為，此為不相稱之電荷密度波 (incommensurate CDW) 所致。相較TbTe3，ErTe3電阻率在低溫處同樣受不相稱之電荷密度波影響而有相似行為。熱導率於高溫電荷密度波相變溫度附近有一明顯轉折，我們透過Wiedemann-Franz Law計算電子熱導率，可得知電子熱導率為主要貢獻。熱電勢於量測溫度區間內皆為正值，顯示其主要傳輸載子為電洞，相變時受費米面附近態度密影響而有明顯變化，此結果也顯示出費米面對電荷密度波變化很敏感。從比熱量測結果可得知電荷密度波相變為二階相變，並利用愛因斯坦模型擬合出背景曲線，得知相變之熵值變化量。比熱實驗結果也可以比較平均場理論預測之比熱變化量。綜合實驗結果顯示，RTe3系列樣品是屬於強耦合的二維電荷密度波系統。

Charge-density waves (CDW) usually occur in low-dimensional materials because of their special anisotropic crystal structure and electronic band structure. In this thesis, we report on the measurements of electrical resistivity (), Seebeck coefficient (S), thermal conductivity (), and specific heat (CP) on the rare-earth tellurides RTe3 (R = Tb, Er) in the temperature range 10 - 400 K. For all measured thermal and transport properties, pronounced anomalous features due to CDW formation were observed in TbTe3. On the other hand, ErTe3 was found to have a second CDW transition at a lower temperature. Comparing the mean-field prediction of the specific-heat jump and BCS weak electron-phonon coupling, the strong electron-phonon coupling plays a significant role in the CDW in TbTe3 and ErTe3.

第一章 前言 1
1-1 簡介 1
1-2 實驗動機 5
第二章 實驗原理 7
2-1 電荷密度波 7
2-2 電阻率 10
2-2-1 電子的碰撞機制 12
2-3 Seebeck效應 15
2-3-1 Seebeck 係數 18
2-4 熱導率 21
2-4-1 電子對熱導率的影響 23
2-4-2 聲子對熱導率的影響 25
2-5 比熱 28
2-5-1 晶格比熱 29
2-5-2 電子比熱 30
第三章 實驗方法 31
3-1 量測系統與方法 31
3-1-1 低溫冷卻系統 31
3-1-2 電阻率量測方法 33
3-1-3 熱導率量測方法 34
3-1-4 Seebeck係數量測方法 36
3-1-5 比熱量測方法 37
3-1-6 比熱運作頻率之選擇方法 42
3-2 實驗控制程式 44
第四章 實驗結果與討論 51
4-1 電阻率(Electrical resistivity) 51
4-2 比熱(Specific heat) 54
4-3 熱導率(Thermal conductivity) 58
4-4 熱電勢(Seebeck coefficient) 60
第五章 結論 63

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