施溫格玻色子之平均場理論在螺旋自旋系統中的應用

Wei-Cheng Su; 蘇偉誠

請用此 Handle URI 來引用此文件： http://tdr.lib.ntu.edu.tw/jspui/handle/123456789/65769

完整後設資料紀錄

DC 欄位	值	語言
dc.contributor.advisor	胡崇德(Chong-Der Hu)
dc.contributor.author	Wei-Cheng Su	en
dc.contributor.author	蘇偉誠	zh_TW
dc.date.accessioned	2021-06-17T00:11:20Z	-
dc.date.available	2014-08-01
dc.date.copyright	2012-08-01
dc.date.issued	2012
dc.date.submitted	2012-07-12
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dc.identifier.uri	http://tdr.lib.ntu.edu.tw/jspui/handle/123456789/65769	-
dc.description.abstract	我們使用施溫格玻色子之平均場理論來分析在二或三維下具有螺旋自旋結構的布拉菲晶格系統。透過對此晶格系統的漢彌爾頓量做對角化計算，我們得到其平均場下的自由能和低激發態的色散關係，進而找出此系統的磁性序參量。除此之外，我們亦發現一條令人驚艷的關係式，其可說明(反)鐵磁序參量和自旋量之間的關連，且可減少在解此系統的熱力學量時所出現的變數。接著，我們把得到的結果應用在實際的系統上，像是磁電鈣鈦礦—RMnO3 (R為稀土族元素)，來計算其系統的尼爾相變溫度和其它的物理量。在低於尼爾溫度時會發生施溫格玻色子的玻色—愛因斯坦凝聚現象。我們發現其理論計算的數值結果和實驗量測的量很吻合。	zh_TW
dc.description.abstract	We have analyzed the quantum Heisenberg model on the two and three dimensional Bravais lattice in the spiral spin state using the Schwinger boson mean-field theory. By diagonalizing the system’s Hamiltonian, we obtain the general form of the mean-field free energy and the low-lying excitation dispersion relation, and then can find its magnetic order parameters. We have also found the surprising relation between the (anti)ferromagnetic order parameters and the spin quantum order by this model. It can reduce the number of variables in the calculating process. Next, we apply this model to the real systems such as RMnO3 (R denoting rare-earth ions) lattice structure to calculate the Neel temperature and other physical quantities. Below this temperature Bose-Einstein condensation of Schwinger bosons can occur. We find that it has good agreement with the experiment results.	en
dc.description.provenance	Made available in DSpace on 2021-06-17T00:11:20Z (GMT). No. of bitstreams: 1 ntu-101-R99222010-1.pdf: 2172180 bytes, checksum: 6cea237c8c23428c82c42d6569cd6e39 (MD5) Previous issue date: 2012	en
dc.description.tableofcontents	1. Introduction...........................................1 2. Heisenberg Model.......................................4 2.1 General Form..........................................4 2.2 Classical Approach....................................5 3. Theoretical Method.....................................7 3.1 Rotation..............................................7 3.2 Schwinger Boson Representation........................8 3.3 Mean-Field Approximation..............................11 3.4 Transformation and Diagonalization....................14 3.5 Mean-Field Free Energy and Thermodynamic Quantities...16 4. Bose-Einstein Condensation In The Spiral Spin State....19 4.1 Low Temperature Behavior..............................19 4.2 Application to RMnO3 Materials........................21 5. Conclusion.............................................24 Bibliography..............................................26
dc.language.iso	en
dc.subject	螺旋自旋結構	zh_TW
dc.subject	平均場理論	zh_TW
dc.subject	尼爾溫度	zh_TW
dc.subject	施溫格玻色子	zh_TW
dc.subject	玻色—愛因斯坦凝聚	zh_TW
dc.subject	磁電鈣鈦礦	zh_TW
dc.subject	(反)鐵磁	zh_TW
dc.subject	Neel temperature	en
dc.subject	mean-field	en
dc.subject	spiral spin	en
dc.subject	(anti)ferromagnetic	en
dc.subject	RMnO3	en
dc.subject	Schwinger bosons	en
dc.subject	Bose-Einstein condensation	en
dc.title	施溫格玻色子之平均場理論在螺旋自旋系統中的應用	zh_TW
dc.title	The application of the mean-field theory of Schwinger bosons to the spiral spin systems	en
dc.type	Thesis
dc.date.schoolyear	100-2
dc.description.degree	碩士
dc.contributor.oralexamcommittee	張明哲,陳智泓,郭光宇,吳文欽
dc.subject.keyword	施溫格玻色子,平均場理論,螺旋自旋結構,(反)鐵磁,磁電鈣鈦礦,尼爾溫度,玻色—愛因斯坦凝聚,	zh_TW
dc.subject.keyword	Schwinger bosons,mean-field,spiral spin,(anti)ferromagnetic,RMnO3,Neel temperature,Bose-Einstein condensation,	en
dc.relation.page	27
dc.rights.note	有償授權
dc.date.accepted	2012-07-12
dc.contributor.author-college	理學院	zh_TW
dc.contributor.author-dept	物理研究所	zh_TW
顯示於系所單位：	物理學系

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