本實驗透過利用物理性質測量系統(Physics Property Measurement System，PPMS)，針對拓樸絕緣體(topological insulator)Sb2SeTe2進行量測，藉由改變溫度以及外加磁場的大小，觀察線性磁阻(linear magneto-resistance, LMR)和載子濃度(carrier concentration)的變化，探討線性磁阻可能的成因，嘗試了解拓樸絕緣體內部的傳輸性質。
實驗結果顯示在外加磁場達到9 T以及在10 K~250 K的溫度區間內，磁阻皆呈現線性且非飽和(non-saturating)的趨勢。此外，根據實驗結果發現線性磁阻的臨界磁場(critical field，B*)與線性磁阻會隨著溫度改變產生變化。
進一步的研究發現線性磁阻的斜率與載子移動率(mobility)成正比，臨界磁場(B*)與載子移動率成反比，此現象符合Parish-Littlewood 的理論模型預測。推論其原因為樣品內部的不均勻性(fluctuation)導致載子移動率產生浮動，因而造成線性磁阻現象。

The non-saturated and linear magneto-resistance (MR) is observed in Sb2SeTe2 topological insulators from 10 K to 250 K within the external magnetic field reaches 9 T. The crossover magnetic field, B*, of the linear magneto-resistance(MR) increases as temperature increases. The experimental results show that the B* is proportional to the inverse Hall mobility and the magneto-resistance(MR) slope is proportional to the Hall mobility. The experimental result is consistent with the prediction of Parish-Littlewood model.

論文審定書............................................................................................................i
摘要.......................................................................................................................ii
Abstract………................................................................................................…...iii
目錄.......................................................................................................................iv
圖次.......................................................................................................................vi
表次.......................................................................................................................viii
第一章 簡介...........................................................................................................1
1-1前言................................................................................................................1
1-2動機................................................................................................................2
1-3文獻回顧.........................................................................................................3
第二章 基本理論....................................................................................................4
2-1霍爾效應(Hall effect) [7]..................................................................................4
2-2量子霍爾效應(Quantum Hall effect)................................................................5
2-3量子自旋霍爾效應(Quantum spin Hall effect)..................................................7
2-4拓樸絕緣體(topological insulator)....................................................................8
2-5線性磁阻(Linear magneto-resistance)............................................................10
2-5-1 Abrikosov量子線性磁阻(Quantum linear magnetoresistance) [17]...........10
2-5-2 Wang & Lei 線性磁阻模型 [19]..................................................................12
2-5-3 Parish & Littlewood理論 [22].....................................................................14
第三章 實驗流程與儀器介紹.................................................................................16
3-1樣品製備..........................................................................................................16
3-2物理性質量測系統(PPMS)...............................................................................17
第四章 實驗結果與討論.........................................................................................20
4-1實驗架構..........................................................................................................20
4-2電阻隨溫度的變化............................................................................................21
4-3霍爾量測結果...................................................................................................22
4-4線性磁阻(linear magnetoresistance)分析........................................................24
4-4-1線性磁阻定義.............................................................................................24
4-4-2 Abrikosov量子線性磁阻理論.....................................................................25
4-4-3 Wang & Lei理論........................................................................................31
4-4-4 Parish & Littlewood 理論..........................................................................33
第五章 結論............................................................................................................35
參考文獻.................................................................................................................36

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