硼或氮掺杂的锯齿型石墨烯纳米带的非共线磁序与电子输运性质
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摘要
基于非共线磁序密度泛函/非平衡格林函数方法,研究了硼或氮掺杂的锯齿型石墨烯纳米带的非共线磁序与电子透射系数.未掺杂的石墨烯纳米带的计算结果表明磁化分布主要遵循类似于Neel磁畴壁的螺旋式磁化分布.相比于未掺杂的情况,硼/氮掺杂的石墨烯纳米带的磁化分布出现了双区域的特征,即杂质原子附近的磁化较小,杂质原子左(右)侧区域的磁化分布更接近于左(右)电极的磁化方向,这为通过掺杂手段在石墨烯纳米带边缘上构建不同磁畴壁提供了可能性.与未掺杂的透射系数不同的是,硼/氮掺杂的石墨烯纳米带的透射系数在费米面附近随着磁化偏转角增大而减小,表明非共线磁序引起的自旋翻转散射占据主导地位.而在E=±0.65 eV处,出现了一个较宽的dip结构,投影电子态密度的分析表明其来源于杂质原子形成的束缚态所引起的背散射.我们的研究结果对于理解石墨烯纳米带中的非共线磁序与杂质散射以及器件设计具有一定的意义.
Zigzag graphene nanoribbon(ZGNR) is important for novel carbon-based spintronic applications.Currently, most of ZGNR spintronic studies focus on the collinear magnetism where the up-spin and down-spin are separated clearly. But in some cases, e.g. doping and adsorption, the magnetization profile can be modulated and thus noncollinear magnetism can occur. In order to shed light on possible noncollinear magnetism in ZGNR,we study non-collinear magnetism and electronic transport of boron or nitrogen-doped zigzag graphene nanoribbon based on noncollinear density functional theory and non-equilibrium Green's function method. For pristine ZGNR, our results show that the ZGNR presents helical magnetization distribution due to noncollinear magnetization in left and right lead. As the ZGNR is doped with boron and nitrogen atoms, the ZGNR shows a characteristic two-zone feature in the magnetization distribution. Near the dopant site, the magnetic moment of carbon atom is small. However, the magnetic moments of carbon atoms in the left(right) region of dopant are close to those of the left(right) lead. Such a feature provides the possibility of constructing domain walls with various widths on the edge of ZGNR. Moreover, the transmission at the Fermi level(E = 0 eV) decreases with the increase of relative angle between magnetizations of left and right lead, indicating that the spin-flip scattering dominates the electronic transport. However, at E = ±0.65 eV, there is a transmission dip with low transmission, which implies that the dopant induces the strong backscattering. To understand the origin of this dip, we calculate the density of states(DOS) and project the DOS onto each atom of doped ZGNR. The projected DOS shows a large and broad peak at E =-0.65 eV for N-doped ZGNR but at E = +0.65 eV for Bdoped ZGNR. The consistency between the position of dip in transmission and the position of peak in DOS indicates that the transmission dip mentioned above is attributed to strong backscattering from the dopantinduced bound state. Our theoretical results are expected to be useful for understanding the noncollinear magnetism and spin scattering in the doped ZGNR-based devices. Also, our work provides a considerable insight into the design of ZGNR-based nanoelectronic devices, such as the transistor based on spin transfer torque effect.
Zigzag graphene nanoribbon(ZGNR) is important for novel carbon-based spintronic applications.Currently, most of ZGNR spintronic studies focus on the collinear magnetism where the up-spin and down-spin are separated clearly. But in some cases, e.g. doping and adsorption, the magnetization profile can be modulated and thus noncollinear magnetism can occur. In order to shed light on possible noncollinear magnetism in ZGNR,we study non-collinear magnetism and electronic transport of boron or nitrogen-doped zigzag graphene nanoribbon based on noncollinear density functional theory and non-equilibrium Green's function method. For pristine ZGNR, our results show that the ZGNR presents helical magnetization distribution due to noncollinear magnetization in left and right lead. As the ZGNR is doped with boron and nitrogen atoms, the ZGNR shows a characteristic two-zone feature in the magnetization distribution. Near the dopant site, the magnetic moment of carbon atom is small. However, the magnetic moments of carbon atoms in the left(right) region of dopant are close to those of the left(right) lead. Such a feature provides the possibility of constructing domain walls with various widths on the edge of ZGNR. Moreover, the transmission at the Fermi level(E = 0 eV) decreases with the increase of relative angle between magnetizations of left and right lead, indicating that the spin-flip scattering dominates the electronic transport. However, at E = ±0.65 eV, there is a transmission dip with low transmission, which implies that the dopant induces the strong backscattering. To understand the origin of this dip, we calculate the density of states(DOS) and project the DOS onto each atom of doped ZGNR. The projected DOS shows a large and broad peak at E =-0.65 eV for N-doped ZGNR but at E = +0.65 eV for Bdoped ZGNR. The consistency between the position of dip in transmission and the position of peak in DOS indicates that the transmission dip mentioned above is attributed to strong backscattering from the dopantinduced bound state. Our theoretical results are expected to be useful for understanding the noncollinear magnetism and spin scattering in the doped ZGNR-based devices. Also, our work provides a considerable insight into the design of ZGNR-based nanoelectronic devices, such as the transistor based on spin transfer torque effect.
引文
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[2] Wang W X, Zhou M, Li X Q, Li S Y, Wu X S, Duan W H,He L 2016 Phys. Rev. B 93 241403
[3] Cui P, Zhang Q, Zhu H B, Li X X, Wang W Y, Li Q X, Zeng C G, Zhang Z Y 2016 Phys. Rev. Lett. 116 026802
[4] Pan J B,Du S X,Zhang Y Y,Pan L D,Zhang Y F,Gao H J, Pantelides S T 2015 Phys. Rev. B 92 205429
[5] Chen X B, Liu Y Z, Gu B L, Duan W H, Liu F 2014 Phys.Rev. B 90 121403
[6] Wang Z F, Jin S, Liu F 2013 Phys. Rev. Lett. 111 096803
[7] Yue Q, Chang S G, Tan J C, Qin S Q, Kang J, Li J B 2012Phys. Rev. B 86 235448
[8] Hu X H, Zhang W, Sun L T, Krasheninnikov A V 2012 Phys.Rev. B 86 195418
[9] Hu T, Zhou J, Dong J M, Kawazoe Y 2012 Phys. Rev. B 86125420
[10] Zheng X H, Wang X L, Huang L F, Hao H, Lan J, Zeng Z2012 Phys. Rev. B 86 081408
[11] Zhou J, Hu T, Dong J M, Kawazoe Y 2012 Phys. Rev. B 86035434
[12] Liu Y, Wang G, Huang Q S, Guo L W, Chen X L 2012 Phys.Rev. Lett. 108 225505
[13] Cheng Y C, Wang H T, Zhu Z Y, Zhu Y H, Han Y, Zhang X X, Schwingenschlgl U 2012 Phys. Rev. B 85 073406
[14] Xiang H J, Huang B, Li Z Y, Wei S H, Yang J L, Gong X G2012 Phys. Rev. X2 011003
[15] Zhang J C, Huang X P, Yue Y A, Wang J M, Wang X W2011 Phys. Rev. B 84 235416
[16] Lin X Q, Ni J 2011 Phys. Rev. B 84 075461
[17] Li Y C, Chen X B, Zhou G, Duan W H, Kim Y, Kim M, Ihm J 2011 Phys. Rev. B 83 195443
[18] Li W, Sevinli H, Roche S, Cuniberti G 2011 Phys. Rev. B 83155416
[19] Zhang Z H, Guo W L, Zeng X C 2010 Phys. Rev. B 82235423
[20] Wang Z F, Li Q X, Zheng H X, Ren H, Su H B, Shi Q W,Chen J 2007 Phys. Rev. B 75 113406
[21] Fujita M, Wakabayashi K, Nakada K, Kusakabe K 1996 J.Phys. Soc. Jpn. 65 1920
[22] Tombros N, Jozsa C, Popinciuc M, Jonkman H T, van Wees B J 2007 Nature 448 571
[23] Huang B, Liu F, Wu J, Gu B L, Duan W H 2008 Phys. Rev.B 77 153411
[24] Ozaki T, Nishio K, Weng H M, Kino H 2010 Phys. Rev. B 81075422
[25] Deng X Q, Sun L, Li C X 2016 Acta Phys. Sin. 65 068503(in Chinese)[邓小清,孙琳,李春先2016物理学报65 068503]
[26] Li B, Xu D H, Zeng H 2014 Acta Phys. Sin. 63 117102(in Chinese)[李彪,徐大海,曾晖2014物理学报63 117102]
[27] Lin Q, Chen Y X, Wu J B, Kong Z M 2011 Acta Phys. Sin.60 097103(in Chinese)[林琦,陈余行,吴建宝,孔宗敏2011物理学报60 097103]
[28] Li J, Zhang Z H, Wang C Z, Deng X Q, Fan Z Q 2013 Acta Phys.Sin. 62 036103(in Chinese)[李骏,张振华,王成志,邓小清,范志强2013物理学报62 036103]
[29] Hu X H, Xu J M, Su L T 2012 Acta Phys. Sin. 61 047106(in Chinese)[胡小会,许俊敏,孙立涛2012物理学报61 047106]
[30] Wang D, Zhang Z H, Deng X Q, Fan Z Q 2013 Acta. Phys.Sin. 62 207101(in Chinese)[王鼎,张振华,邓小清,范志强2013物理学报62 207101]
[31] Yazyev 0 V, Katsnelson M I 2008 Phys. Rev. Lett. 100047209
[32] Zhang Y, Yan X H, Guo Y D, Xiao Y 2017 J. Appl. Phys.121 174303
[33] Li H D, Wang L, Lan Z H, Zheng Y S 2009 Phys. Rev. B 79155429
[34] Xu B, Yin J, Weng H G, Xia Y D, Wan X G, Liu Z G 2010Phys. Rev. B 81 205419
[35] Wang B, Wang J, Guo H 2009 Phys. Rev. B 79 165417
[36] Ozaki T, Kino H 2005 Phys. Rev. B 72 045121
[37] Tersoff J, Hamann D R 1985 Phys. Rev. B 31 805
[38] Chantis A N, Smith D L, Fransson J, Balatsky A V 2009Phys. Rev. B 79 165423
[39] Slonczewski J C 1989 Phys. Rev. B 39 6995
[40] Press M R, Liu F, Khanna S N, Jena P 1989 Phys. Rev. B 40399