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    Title: 自旋電子元件之內部效應與外界作用對自旋分裂現象的影響
    Other Titles: Internal Effects and External Forces on Spin Splitting of Spintronics
    Authors: 陳俊男
    Contributors: 淡江大學物理學系
    Keywords: 自旋電子;自旋分裂;Dresselhaus;Rashba;磁場;電場;應力;摻雜濃度;Spintronics;Spin Splitting;Dresselhaus;Rashba;Magnetic Field;Electrical Field;Strain;Doping Concentration
    Date: 2007
    Issue Date: 2009-03-16 12:04:52 (UTC+8)
    Abstract: 自旋電子之自旋分裂現象,其受到內部效應﹝Dresselhaus,Rashba,和應力效應﹞與外界作用﹝電場,磁場,和摻雜濃度﹞的影響,將被探討。在無磁場與電場情況下,自旋軌道耦合與反非對稱性﹝Rashba與Dresselhaus效應﹞亦能造成自旋分裂。而自旋分裂的大小,可以用外界作用﹝電場,磁場,和摻雜濃度﹞來控制。經由閘極電壓變化來改變電場,因而造成能帶結構對稱性不同程度的變化,進而產生自旋分裂的變化。外加磁場可產生額外的Zeeman分裂,其可減低對稱性量子井﹝不存在分裂﹞與非對稱性量子井﹝存在分裂﹞的差異。摻雜可造成半導體能帶結構的彎曲變化,因而增進或減低自旋電子元件的自旋分裂大小。適度的應力可降低自旋分裂的大小,其作用力學原因為:應力造成重電洞與輕電洞能帶的位移,進而減低能帶混成程度,因此影響自旋分裂。這些內部效應與外界作用將被探討,進而改進自旋電子元件的功能。 Internal effects (Dresselhaus, Rashba, and strain effects) and external forces (electrical field, magnetic field, and doping concentration) will be explored their effects on the spin splitting of spintronics. Spin-orbit coupling combined with inversion asymmetry (Rashba and Dresselhaus effects) give rise to spin splitting even in the absence of an applied magnetic and electrical field. The size of this spin splitting can be controlled by changing the external forces, such as: electrical field, magnetic field, and doping concentration. The electrical field can change the degree of asymmetry using a gate voltage, and thus the spin splitting can be controlled by the electrical field. An applied magnetic field causes an additional Zeeman splitting, which can erase the difference between a symmetric quantum well (without subband splitting) and an asymmetric quantum well. Doping can induce the band bending of semiconductor heterostructure, and thus it will enhance or decrease the magnitude of the spin splitting of spintronic devices. Applying moderate strain can easily decrease the spin splitting by an order of magnitude. The mechanism is the strain-induced energy shift of the heavy-hole and light-hole subbands, which diminishes the degree of band mixing and found to be strongly correlated to the spin splitting. Those internal effects and external forces will be explored to improve the performance of spintronic devices.
    Appears in Collections:[Graduate Institute & Department of Physics] Research Paper

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