本文選題：二維材料 + 拓?fù)浣^緣體�。� 參考：《山東大學(xué)》2017年博士論文

【摘要】：石墨烯(graphene)是一種由sp2雜化軌道特點的碳原子構(gòu)成的具有六邊形蜂巢結(jié)構(gòu)的二維晶體材料。伴隨著石墨烯的成功剝離,以石墨烯為代表的二維材料成為材料科學(xué)和凝聚態(tài)物理等領(lǐng)域的研究新熱點。石墨烯在費米能級附近的電子能帶結(jié)構(gòu)呈現(xiàn)線性的能量一動量色散關(guān)系,因其滿足描述相對論粒子的狄拉克方程,這種能帶結(jié)構(gòu)被稱為狄拉克錐。石墨烯中的狄拉克錐為二維材料的基礎(chǔ)和應(yīng)用研究提供了一個理想的模型,進(jìn)而促進(jìn)了自旋電子學(xué)和超導(dǎo)現(xiàn)象等領(lǐng)域的發(fā)展�；谑┚Ц竦腍aldane模型和Kane-Mele模型是描述量子反常霍爾態(tài)和量子自旋霍爾態(tài)的最早理論模型,為二維材料中拓?fù)潆娮討B(tài)的后續(xù)研究打下了重要的理論基礎(chǔ);通過應(yīng)變和電荷摻雜可以有效地調(diào)節(jié)石墨烯中電子—聲子耦合強度,這為提高二維超導(dǎo)材料的超導(dǎo)轉(zhuǎn)變溫度提供了新的途徑,推動了超導(dǎo)現(xiàn)象在新型二維材料中的研究進(jìn)展。另外,狄拉克錐特點的能帶結(jié)構(gòu)使石墨烯本身具有優(yōu)異的導(dǎo)熱導(dǎo)電性,促進(jìn)了對其他新型二維狄拉克材料的探索和研究。在二維材料拓?fù)潆娮討B(tài)和超導(dǎo)特性的研究領(lǐng)域,最大程度的增大拓?fù)浞瞧接箮逗统瑢?dǎo)能隙是研究的重點之一。尋找實驗上合成的、具有更大能隙的二維拓?fù)浣^緣體和超導(dǎo)體有利于在更高的工作溫度下實現(xiàn)上述奇異的電子行為,從而為相應(yīng)電子態(tài)的實際應(yīng)用提供材料選擇。同時,探究二維拓?fù)潆娮討B(tài)和超導(dǎo)特性的產(chǎn)生和調(diào)控機制,對于提高拓?fù)鋷逗统瑢?dǎo)能隙或者產(chǎn)生新奇的量子現(xiàn)象具有重要意義,從而為設(shè)計、然后制備出具有更優(yōu)異性能的二維材料提供理論指導(dǎo)。本論文以一系列新型二維材料為研究對象,采用基于密度泛函理論的第一性原理計算方法,對自旋—軌道耦合所導(dǎo)致的拓?fù)浞瞧接剐院碗娮印曌玉詈纤鶎?dǎo)致的超導(dǎo)特性展開了系統(tǒng)的理論預(yù)測和調(diào)控。所取得的代表性成果如下:1、揭示了二維類石墨烯氮化碳材料(Graphitic Carbon Nitrides)中電子能帶結(jié)構(gòu)的調(diào)控規(guī)律,并成功證明了量子反常霍爾態(tài)在這種輕質(zhì)元素材料中存在的可能性。針對實驗上以Heptazine為結(jié)構(gòu)單元合成的二維類石墨烯氮化碳材料(g-C3N4),探討了空穴摻雜和拉伸應(yīng)變對電子自旋極化和磁性耦合方式的調(diào)控規(guī)律。在此基礎(chǔ)上,預(yù)言了兩種具有自旋極化零帶隙半導(dǎo)體(Spin-Gapless Semiconductor)性質(zhì)的二維類石墨烯氮化碳材料:g-C10N9和g-C14N12。這兩種材料具有穩(wěn)定的鐵磁耦合基態(tài),較強的自旋—軌道耦合效應(yīng)在費米能級處打開了陳數(shù)(Chern number)為-1的拓?fù)浞瞧接箮?比石墨烯的拓?fù)鋷洞笕齻�量級,對應(yīng)著更高的工作溫度。因此,量子反常霍爾效應(yīng)有望在這種不含金屬的輕質(zhì)元素材料中實現(xiàn),為氮化碳材料的應(yīng)用打開了新的領(lǐng)域。2、金屬原子和有機配體組成的二維金屬—有機材料(Metal-Organic Frameworks,MOF),具有豐富的晶體結(jié)構(gòu)構(gòu)型和新奇的物理特性。本論文針對具有Kagome晶格的二維有機拓?fù)浣^緣體材料:HTT-Pt,探究了電荷摻雜對這種二維材料的電子自旋極化和拓?fù)涮匦缘恼{(diào)控規(guī)律。從理論上預(yù)言了改變電子摻雜濃度可以導(dǎo)致HTT-Pt發(fā)生從普通絕緣體到量子自旋霍爾絕緣體、再到量子反常霍爾絕緣體的轉(zhuǎn)變。同時,重金屬元素鉑(Pt)使HTT-Pt具有較強的自旋—軌道耦合作用,拓?fù)浞瞧接箮犊梢赃_(dá)到～42.5 meV。因此,通過適當(dāng)?shù)碾娮訐诫s,HTT-Pt有望在較高溫度下實現(xiàn)量子自旋甚至是量子反�；魻栃�(yīng)。3、得益于近年來實驗納米技術(shù)手段的提高,關(guān)于二維材料或者原子層厚度材料超導(dǎo)特性的研究被建立起來,并且取得了巨大的進(jìn)步�；趯嶒炆虾铣傻�、具有優(yōu)異導(dǎo)電性的金屬—有機材料:Cu-BHT,我們首次從理論上預(yù)言了超導(dǎo)特性在MOF中存在的可能性。二維單層Cu-BHT的超導(dǎo)轉(zhuǎn)變溫度(T。)約為4.43K,高于相應(yīng)三維塊體材料的轉(zhuǎn)變溫度(Tc≈1.58K)。對于這種異常的溫度—維度變化規(guī)律,我們也進(jìn)行了相應(yīng)的討論。對于單層Cu-BHT,銅原子和硫原子的低頻振動模式與費米能級附近恰當(dāng)?shù)碾娮討B(tài)之間具有較強的耦合作用;當(dāng)單層Cu-BHT堆垛成三維塊體材料時,較強的層間相互作用破壞了上述電子態(tài),從而削弱了電子—聲子耦合強度。這與界面效應(yīng)等方式提高二維材料超導(dǎo)轉(zhuǎn)變溫度的機制不同,對進(jìn)一步提升二維超導(dǎo)材料的超導(dǎo)能隙具有重要意義。4、基于實驗上合成的C36富勒烯薄膜,成功預(yù)言了一種由準(zhǔn)sp2-sp3軌道雜化碳原子形成的二維狄拉克材料:ph-graphene。與石墨烯類似,碳原子的pz軌道在費米能級處形成了自旋簡并的狄拉克錐,費米速度可以達(dá)到2.8×105m/s。氫原子吸附可以有效調(diào)控其電學(xué)性質(zhì),包括產(chǎn)生電子自旋極化和打開帶隙等。同時,ph-graphene具有"柔軟"特性,面內(nèi)剛度(In-plane Stiffness)不到石墨烯的十分之一,因此有望在柔性電子學(xué)領(lǐng)域得到應(yīng)用。
[Abstract]:Shi Moxi (graphene) is a two-dimensional crystal material with hexagonal honeycomb structure composed of carbon atoms characterized by SP2 hybrid orbits. With the successful stripping of graphene, the two-dimensional material, represented by graphene, has become a new hot spot in the field of material science and condensed matter physics. The band structure presents a linear energy momentum dispersion relation, which satisfies the Dirac equation describing the relativistic particles. This band structure is called the Dirac cone. The Dirac cone in the graphene provides an ideal model for the basis and application of two-dimensional materials, and thus promotes the fields of spintronics and superconductivity. Development. The Haldane model and Kane-Mele model based on the graphene lattice are the earliest theoretical models describing the quantum anomalous Holzer state and the quantum spin Holzer state, which lays an important theoretical basis for the subsequent study of the topological electronic states in the two-dimensional material; the electron phonon coupling in graphene can be effectively regulated through the strain and charge doping. Strength, which provides a new way to improve the superconducting transition temperature of two dimensional superconducting materials, promotes the research progress of superconducting phenomenon in the new two-dimensional material. In addition, the band structure of Dirac cone has made Shi Moxi itself have excellent thermal conductivity and conduce to the exploration and research of his new two-dimensional Dirac material. The research field of the topological electronic state and superconducting properties of two dimensional materials is one of the key points in the study of the maximum increase of topological non mediocre bandgap and superconducting gap. The practical application of the corresponding electronic states provides material selection. At the same time, it is of great significance to explore the generation and regulation mechanism of the two-dimensional topological electronic state and superconducting properties. It is of great significance to improve the topological band gap and superconducting gap, or to produce novel quantum phenomena, thus providing theoretical guidance for the design, and then the preparation of two dimensional materials with more excellent properties. In this paper, a series of new two-dimensional materials are taken as the research object. Using the first principle calculation method based on the density functional theory, the theoretical prediction and regulation of the superconductivity caused by the topological non mediocre and electron phonon coupling caused by the spin orbit coupling are theoretically predicted and regulated. The representative achievements are as follows: 1 The regulation of the electronic band structure in Graphitic Carbon Nitrides is shown, and the possibility of the existence of the quantum abnormal Holzer state in this light element material is proved successfully. On the basis of the regulation of doping and tensile strain on the electron spin polarization and magnetic coupling mode, two two-dimensional graphite like carbon nitride materials with spin polarized zero band gap semiconductor (Spin-Gapless Semiconductor) properties are predicted. The two materials of g-C10N9 and g-C14N12. have stable ferromagnetic coupling ground state, and the stronger self The spin orbit coupling effect opens the topological non ordinary band gap of Chen Shu (Chern number) at Fermi level, which is three orders of magnitude larger than the topological band gap of graphene, corresponding to the higher working temperature. Therefore, the quantum anomalous Holzer effect is expected to be realized in this non metallic light element material and opens the application of the carbon nitride material. A new field of.2, a two-dimensional metal organic material (Metal-Organic Frameworks, MOF), consisting of metal atoms and organic ligands, has a rich crystal structure and novel physical properties. In this paper, a two-dimensional organic topological insulator with Kagome lattice, HTT-Pt, is used to explore the electronic charge doping to this two-dimensional material. The regulation of spin polarization and topological properties has been predicted theoretically that the change of the electron doping concentration can lead to the transformation of HTT-Pt from ordinary insulators to quantum spin Holzer insulators and to quantum abnormal Holzer insulators. At the same time, the heavy metal element platinum (Pt) has a strong spin orbit coupling effect on the HTT-Pt, and the topology is not flat. The mean band gap can reach to 42.5 meV., so HTT-Pt is expected to achieve quantum spin and even quantum abnormal Holzer effect at higher temperatures by proper electron doping. Thanks to the improvement of the experimental nanotechnology in recent years, the study of the superconductivity of two dimensional materials or atomic layer thickness materials has been established and obtained. Great progress. Based on an experimentally synthesized metal organic material with excellent conductivity, Cu-BHT, we have theoretically predicted the possibility of the existence of superconductivity in MOF for the first time. The superconductivity transition temperature (T.) of a two-dimensional single layer Cu-BHT is about 4.43K, higher than the transition temperature of the corresponding three-dimensional bulk material (Tc 1.58K). For a single Cu-BHT, the low-frequency vibration modes of copper and sulfur atoms are strongly coupled with the appropriate electronic states near the Fermi level for a single layer of copper. When a single layer of Cu-BHT is stacked into a three-dimensional bulk material, the strong interlayer interaction destroys the above electronic state. It weakens the electron phonon coupling strength, which is different from the mechanism of improving the superconducting transition temperature of two-dimensional materials, such as the interface effect, and is of great significance to the further enhancement of the superconducting gap of the two-dimensional superconducting material. Based on the experimental synthesis of the C36 fullerene film, a kind of quasi sp2-sp3 orbital hybrid carbon atoms has been successfully prefaced. The two-dimensional Dirac material: ph-graphene. is similar to graphene. The PZ orbit of the carbon atom forms a spin degenerate Dirac cone at Fermi level. The Fermi velocity can reach 2.8 * 105m/s. hydrogen adsorption, which can effectively regulate its electrical properties, including the generation of electron spin polarization and opening of the band gap. At the same time, the ph-graphene has "softness". The In-plane Stiffness is less than 1/10 of graphene, so it is expected to be applied in the field of flexible electronics.
【學(xué)位授予單位】：山東大學(xué)
【學(xué)位級別】：博士
【學(xué)位授予年份】：2017
【分類號】：O469

【參考文獻(xiàn)】

相關(guān)期刊論文 前1條

1 Jinying Wang;Shibin Deng;Zhongfan Liu;Zhirong Liu;;The rare two-dimensional materials with Dirac cones[J];National Science Review;2015年01期

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本文編號：1913831