本文關(guān)鍵詞：拓撲材料中拓撲量子相變和輸運性質(zhì)的研究　出處：《南京大學(xué)》2017年博士論文　論文類型：學(xué)位論文

  更多相關(guān)文章： 拓撲絕緣體 自旋陳數(shù) 拓撲晶態(tài)絕緣體 拓撲量子相變 谷電子學(xué) 拓撲泵浦 逆自旋霍爾效應(yīng) 逆Edelstein效應(yīng)

【摘要】：拓撲絕緣體是一種新奇的物質(zhì)的態(tài),它們的體能帶與普通絕緣體一樣存在能隙,但在邊界處存在無能隙的邊界態(tài),這是由其能帶結(jié)構(gòu)的非平庸拓撲性質(zhì)決定的。拓撲絕緣體由拓撲不變量Z2或自旋陳數(shù)來刻畫。它的邊界態(tài)由能帶拓撲性和時間反演對稱性所保護,因此不被非磁雜質(zhì)散射,另外,邊界態(tài)還具有螺旋結(jié)構(gòu),即動量和自旋是綁定的,這些性質(zhì)在自旋電子學(xué)領(lǐng)域有廣泛的應(yīng)用。拓撲絕緣體在理論預(yù)言后不久,就在實驗上被證實,并被推廣到三維系統(tǒng)。它的迅速發(fā)展吸引的廣泛的興趣。受拓撲絕緣體的啟發(fā),人們將能帶結(jié)構(gòu)的分類擴展到了另一個方向——包括晶格對稱性,并稱這類由晶格對稱性保護的拓撲絕緣體為“拓撲晶態(tài)絕緣體”。人們還預(yù)言了存在拓撲晶態(tài)絕緣相的真實材料,相關(guān)預(yù)言已被實驗證實。另外,在二維蜂房格子系統(tǒng)中除了電荷自由度和自旋自由度,還存在著谷自由度,最近很多與谷相關(guān)的拓撲相變已經(jīng)在理論上提出來了,利用這些谷相關(guān)的拓撲相,人們還設(shè)計了有趣的電子器件。在第二章中,我們討論了在Zeeman場下拓撲晶態(tài)絕緣體SnTe表面態(tài)的拓撲性質(zhì)。發(fā)現(xiàn)通過調(diào)節(jié)Zeeman場的方向,可以實現(xiàn)谷相關(guān)的拓撲相變。用贗自旋陳數(shù)描寫系統(tǒng)的拓撲性質(zhì),我們得到半徑為B的相球,其中包含陳數(shù)C=2的量子反常霍爾態(tài),陳數(shù)C=1的量子反�；魻枒B(tài),量子贗自旋霍爾態(tài),以及平庸拓撲絕緣體態(tài)。在C=1量子反�；魻枒B(tài)和平庸絕緣體態(tài)中,兩個谷處于不同的拓撲態(tài)。這種谷相關(guān)的拓撲相為設(shè)計低耗散的電子學(xué)器件以及基于拓撲晶態(tài)絕緣體的谷電子學(xué)應(yīng)用提供了新的平臺。拓撲絕緣體由拓撲不變量Z2指標(biāo)或自旋陳數(shù)來刻畫。然而,不同于描寫量子霍爾效應(yīng)的第一類陳數(shù),到目前為止,這些拓撲不變量還未被直接測量和利用,雖然有幾個方案已經(jīng)提出來去觀察它們。所以,測量這些拓撲不變量的更簡單實用方法是值得期待的。在第三章,我們提出在硅烯中的拓撲泵浦效應(yīng),以直接測量系統(tǒng)的拓撲不變量。我們考慮在硅烯中施加兩個含時電場,其中一個交變電場處于硅原子所在平面內(nèi),大小為Ey,另一個電場垂直平面,包含兩部分,靜電場和交變場,大小分別為E0z和E1z。使用自旋-谷陳數(shù)特征系統(tǒng)的拓撲性質(zhì),我們可以看到這個系統(tǒng)可以處于純的谷泵浦態(tài),混合的自旋-谷泵浦態(tài),以及平庸泵浦態(tài),由垂直電場的強度E0z和E1z決定。由散射矩陣計算的每個循環(huán)泵浦的谷和自旋總量與自旋-谷陳數(shù)描寫完全一致。這個總量正比于樣品的寬度,對材料參數(shù)不敏感,這說明了泵浦是一種體效應(yīng),與邊緣態(tài)無關(guān)。自旋霍爾效應(yīng)是由于自旋-軌道耦合,電荷流引起橫向自旋流的物理現(xiàn)象。這種效應(yīng)為產(chǎn)生自旋流提供了一種電學(xué)方法。基于相同的物理機制,純自旋流也可以產(chǎn)生橫向電荷流或可測量的電勢差,這稱為逆自旋霍爾效應(yīng)。在第四章,我們發(fā)展了一套理論來描寫B(tài)i2Se3薄膜表面態(tài)的逆自旋霍爾效應(yīng)。我們將Bi2Se3連接到電子庫,對電子庫施加自旋偏壓,自旋偏壓通過它在通道本征態(tài)子空間的投影驅(qū)動電子輸運。我們說明了拓撲表面態(tài)是逆自旋霍爾效應(yīng)的理想平臺,由于拓撲絕緣體表面態(tài)的自旋-動量綁定,這里自旋偏壓完全可以轉(zhuǎn)換為可測量的橫向電壓,使拓撲絕緣體內(nèi)縱向自旋流為零。我們的理論解釋了實驗上在拓撲絕緣體內(nèi)觀察到的大自旋霍爾角。此外,完美的逆Edelstein效應(yīng),即完整的自旋-電荷轉(zhuǎn)換也可發(fā)生在表面態(tài)。在本文的最后一章,我們做了一個簡單的總結(jié)和展望。
[Abstract]:Topological insulator is a kind of novel material state, and there exists a gap in their ordinary insulator as the Fitness Zone, but there are gapless boundary state at the boundary, which is decided by the non trivial topological properties of its band structure. The topological invariants of topological insulator Z2 or spin numbers to describe boundary state it. Chen the band topology and time reversal symmetry protection, and therefore is not a nonmagnetic impurity scattering, in addition, the boundary state also has spiral structure, namely momentum and spin is bound, these properties have been widely applied in the field of spintronics. Topological insulator shortly after the theoretical prediction is confirmed in. In experiment, and was extended to three-dimensional system. Its rapid development attracted wide interest. Inspired by the topological insulator, the classification of the band structure of people will extend to another direction, including the lattice symmetry, and called it by Topological insulator lattice symmetry protection "topological crystalline insulator". People also predicted the existence of amorphous insulating material phase real topology, the relevant predictions have been experimentally verified. In addition, in the two-dimensional honeycomb lattice system in addition to the degrees of freedom of charge and spin degrees of freedom, there are still many degrees of freedom and the valley, the valley recently in the theory of topological phase has been proposed, using the topology corresponding to the valley, people also design interesting electronic devices. In the second chapter, we discuss the Zeeman in the field of topological insulator amorphous surface states of SnTe topological properties. By adjusting the Zeeman field direction, can achieve Valley topological phase correlation the description of topological properties of systems with pseudo spin Chen Shu, we obtain the radius of ball B, which contains the quantum anomalous Holzer state Chen Shu C=2, Holzer Chen Shu C=1 state quantum anomalous, quantum pseudo self Holzer spin state, and the insulating body. Trivial topology in C=1 quantum anomalous Holzer state and mediocre insulation posture, two in the valley. The valley of different topological state related topological phase for electronics design and application of low dissipation valleytronics amorphous insulator based on topology provides a new platform to characterize topological insulators. A topological invariant Z2 index or spin Chen Shu. However, different from the first class Chen Shu description of quantum Holzer effect, so far, these topological invariants have not been directly measured and utilized, although several solutions have been proposed to observe them. Therefore, more simple and practical method for measuring these topological invariants is worth looking forward to. The third chapter, we propose the topology in the pump effect of silylenes, with topological invariants of a direct measurement system. We consider two applied time-dependent electric field in silylenes, one of the An alternating electric field in silicon atoms within the plane, vertical plane size is Ey, another electric field, consists of two parts, electrostatic field and magnetic field, the size of topological properties of E0z and E1z. using spin - Chen Shu Valley features of the system, we can see that this system can be in the valley of pumped state pure, mixed spin the valley - pumped state and mediocre pumped state by the vertical electric field strength of E0z and E1z. Each cycle pump is calculated from the scattering matrix of the valley and the total spin and spin Valley Chen Shu describes exactly the same. The total amount is proportional to the width of the sample, is not sensitive to the material parameters, which indicates that the pump is a kind of body the effect that has nothing to do with the edge state. The Holzer effect is due to the spin spin orbit coupling, charge flow caused by the physical phenomenon of transverse spin flow. This effect provides a method for producing electrical spin current based on the same physical mechanism, Pure spin can also produce potential lateral charge flow or can be measured, which is called the inverse spin Holzer effect. In the fourth chapter, the inverse spin Holzer effect, we develop a theory to describe the surface state of Bi2Se3 thin films. We connect the Bi2Se3 to the electronic library, electronic, and spin spin bias, bias drive the electron transport in the eigenstates of the subspace projection channel through it. We show that the topological state is an ideal platform for the inverse Holzer effect due to spin, spin momentum topological insulator surface state binding, here the spin bias can be converted to a completely transverse voltage can be measured, the topological insulator longitudinal spin current is zero our theory explains the experimental topology in the insulation of large spin Holzer observed in vivo angle. In addition, inverse Edelstein effect is perfect, i.e. complete spin charge transfer can also occur in the surface state in this paper. In the last chapter, we have made a simple summary and prospect.

【學(xué)位授予單位】：南京大學(xué)
【學(xué)位級別】：博士
【學(xué)位授予年份】：2017
【分類號】：O469

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