氮化硼纳米带功能化碳纳米管的热自旋输运性质
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摘要
热自旋电子学器件结合了自旋电子学和热电子学各自的优点,对人类可持续发展具有重要作用.本文研究了锯齿形BN纳米带(ZBNRs)共价功能化碳纳米管(SWCNT)的电子结构,发现ZBNRs-B-(6,6)SWCNT为磁性半金属,nZBNRs-B-(6,6)SWCNT(n=2—8)为磁性金属;nZBNRs-N-(6,6)SWCNT(n=1—8)为双极化铁磁半导体;4ZBNRs-B-(4,4)SWCNT和4ZBNRs-N-(4,4)SWCNT为磁性半金属,4ZBNRs-B-(m,m)SWCNT(m=5—9)为磁性金属;4ZBNRs-N-(m,m)SWCNT(m=5—9)为双极化铁磁半导体.然后,基于锯齿形BN纳米带共价功能化碳纳米管设计了新型热自旋电子学器件,发现基于ZBNRs-N-(6,6)SWCNT的器件具有热自旋过滤效应;而8ZBNRs-N-(6,6)SWCNT和nZBNRs-B-(6,6)SWCNT(n=1,8)都存在自旋相关塞贝克效应.这些发现表明BN纳米带功能化碳纳米管在热自旋电子学器件方面具有潜在的应用.
The spin caloritronics device, because of the characteristics of spintronics and thermoelectronics, plays an important role in human sustainable development. A lot of spin caloritronic devices based carbon materials(such as graphene nanoribbons, carbon nanotubes) have been reported. However, there are few studies of the thermal spin transport properties in a hybrid structure of single-walled carbon nanotubes and zigzag-edge BN nanoribbons, and the thermal spin transport mechanism of this structure is still unclear. In this paper, using the nonequilibrium Green's function(NEGF) combined with the first principle calculations, the electronic structures and the thermal spin transport properties of the zigzag edge BN nanoribbons functionalized single-walled carbon nanotubes are studied. It is shown that the ZBNRs-N-(6, 6)SWCNT is a half-metal, while the n ZBNRs-N-(6,6)SWCNT are magnetic metals(n = 2-8), and the n ZBNRs-B-(6, 6)SWCNT are bipolar magnetic semiconductors(n = 1-8). The 4 ZBNRs-N-(4, 4)SWCNT and 4 ZBNRs-B-(4, 4)SWCNT are half-metals, while the 4 ZBNRs-B-(m, m)SWCNT(m = 5-9)are magnetic metals, and the 4 ZBNRs-N-(m, m)SWCNT(m = 5-9)are bipolar magnetic semiconductors. Then, some novel spin caloritronicdevices are designed based on n ZBNRsN-(6, 6)SWCNT and n ZBNRs-B-(6, 6)SWCNT(n = 1, 8). For the ZBNRs-B-(6, 6)SWCNT, when the temperature of the left electrode is increased above a critical value, the thermal spin-up current then increases remarkably from zero. Meanwhile the thermal spin-down current remains approximately equal to zero in the entire temperature region, thus indicating the formation of a thermal spin filter. For the 8 ZBNRs-N-(6,6)SWCNT and n ZBNRs-B-(6, 6)SWCNT(n = 1, 8), when a temperature gradient is produced between two electrodes, the spin-up and spin-down currents are driven in the opposite directions, which indicates that the spin-dependent Seebeck effect(SDSE) appears. In order to obtain the fundamental mechanism of thermal spin filter effect and SDSE, the Landauer-Büttiker formalism is adopted. It is found that the currents(Iup and Idn)mainly depend on two factors: 1)the transport coefficient; 2) the difference between the Fermi-Dirac distributions of the left and right electrode. Additionally, the electron current Ie and the hole current Ih will be generated when a temperature gradient is produced between the left and right lead. Furthermore, the Iup and Idn have the opposite directions for the spin up transmission peaksbelow the Fermi level while they have the opposite directions for the spin down transmission peaks above the Fermi level in the transmission spectrum,which demonstrates the presence of the SDSE in the 8 ZBNRs-B-(6, 6)SWCNT and n ZBNRs-N-(6, 6)SWCNT(n = 1, 8). Finally, the results indicate that n ZBNR-N-(m, m)SWCNT and n ZBNR-B-(m, m)SWCNT can have potential applications in thermospin electronic devices.
The spin caloritronics device, because of the characteristics of spintronics and thermoelectronics, plays an important role in human sustainable development. A lot of spin caloritronic devices based carbon materials(such as graphene nanoribbons, carbon nanotubes) have been reported. However, there are few studies of the thermal spin transport properties in a hybrid structure of single-walled carbon nanotubes and zigzag-edge BN nanoribbons, and the thermal spin transport mechanism of this structure is still unclear. In this paper, using the nonequilibrium Green's function(NEGF) combined with the first principle calculations, the electronic structures and the thermal spin transport properties of the zigzag edge BN nanoribbons functionalized single-walled carbon nanotubes are studied. It is shown that the ZBNRs-N-(6, 6)SWCNT is a half-metal, while the n ZBNRs-N-(6,6)SWCNT are magnetic metals(n = 2-8), and the n ZBNRs-B-(6, 6)SWCNT are bipolar magnetic semiconductors(n = 1-8). The 4 ZBNRs-N-(4, 4)SWCNT and 4 ZBNRs-B-(4, 4)SWCNT are half-metals, while the 4 ZBNRs-B-(m, m)SWCNT(m = 5-9)are magnetic metals, and the 4 ZBNRs-N-(m, m)SWCNT(m = 5-9)are bipolar magnetic semiconductors. Then, some novel spin caloritronicdevices are designed based on n ZBNRsN-(6, 6)SWCNT and n ZBNRs-B-(6, 6)SWCNT(n = 1, 8). For the ZBNRs-B-(6, 6)SWCNT, when the temperature of the left electrode is increased above a critical value, the thermal spin-up current then increases remarkably from zero. Meanwhile the thermal spin-down current remains approximately equal to zero in the entire temperature region, thus indicating the formation of a thermal spin filter. For the 8 ZBNRs-N-(6,6)SWCNT and n ZBNRs-B-(6, 6)SWCNT(n = 1, 8), when a temperature gradient is produced between two electrodes, the spin-up and spin-down currents are driven in the opposite directions, which indicates that the spin-dependent Seebeck effect(SDSE) appears. In order to obtain the fundamental mechanism of thermal spin filter effect and SDSE, the Landauer-Büttiker formalism is adopted. It is found that the currents(Iup and Idn)mainly depend on two factors: 1)the transport coefficient; 2) the difference between the Fermi-Dirac distributions of the left and right electrode. Additionally, the electron current Ie and the hole current Ih will be generated when a temperature gradient is produced between the left and right lead. Furthermore, the Iup and Idn have the opposite directions for the spin up transmission peaksbelow the Fermi level while they have the opposite directions for the spin down transmission peaks above the Fermi level in the transmission spectrum,which demonstrates the presence of the SDSE in the 8 ZBNRs-B-(6, 6)SWCNT and n ZBNRs-N-(6, 6)SWCNT(n = 1, 8). Finally, the results indicate that n ZBNR-N-(m, m)SWCNT and n ZBNR-B-(m, m)SWCNT can have potential applications in thermospin electronic devices.
引文
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[3]Ezawa M 2009 Eur.Phys.B 67 543
[4]Borlenghi S,Wang W W,Fangohr H,Bergqvist L,Delin A2014 Phys.Rev.Lett.112 047203
[5]Fu H H,Wu D D,Gu L,Wu M H,Wu R 2015 Phys.Rev.B92 045418
[6]Ren J 2013 Phys.Rev.B 88 220406(R)
[7]Ren J,Zhu J X 2013 Phys.Rev.B 87 241412(R)
[8]Fu H H,Gu L,Wu D D 2016 Phys.Chem.Chem.Phys.1812742
[9]Ren J,Fransson J,Zhu J X 2014 Phys.Rev.B 89 214407
[10]Wu D D,Liu Q B,Fu H H,Wu R 2017 Nanoscale 9 18334
[11]Liu Q B,Wu D D,Fu H H 2017 Phys.Chem.Chem.Phys.1927132
[12]Avouris P,Chen Z,Perebeinos V 2007 Nat.Nanotechnol.2605
[13]Nair R R,Blake P,Grigorenko A N,Novoselov K S,Booth TJ,Stauber T,Peres N M R,Geim A K 2008 Science 320 1380
[14]Cai J,Ruffieux P,Jaafar R,Bieri M,Braun T,Blankenburg S,Muoth M,Seitsonen A P,Saleh M,Feng X,Müllen K,Fasel R 2010 Nature 466 470
[15]Zeng M G,Feng Y P,Liang G C 2011 Nano Lett.11 1369
[16]Zeng M G,Shen L,Zhou M,Zhang C,Feng Y P 2011 Phys.Rev.B 83 115427
[17]Zeng M,Feng Y,Liang G 2011 Appl.Phys.Lett.99 123114
[18]Ni Y,Yao K L,Fu H H,Gao G Y,Zhu S C,Wang S L 2013Sci.Rep.3 1380
[19]Li J W,Wang B,Xu F M,Wei Y D,Wang J 2016 Phys.Rev.B 93 195426
[20]Liu Q B,Wu D D,Fu H H 2017 Phys.Chem.Chem.Phys.1927132
[21]Tang X Q,Ye X M,Tan X Y,Ren D H 2018 Sci.Rep.8 927
[22]Lou P 2014 Phys.Status Solidi RRL 8 187
[23]Zeng H L,Gou Y D,Yan X H,Zhou J 2017 Phys.Chem.Chem.Phys.19 21507
[24]Taylor J,Guo H,Wang J 2001 Phys.Rev.B 63 121104(R)
[25]Padilha J E,Lima M P,Silva A J R D,Fazzio A 2011 Phys.Rev.B 84 113412
[26]Soler J M,Artacho E,Gale J D,García A,Junquera J,Ordejón P,Sánchez-Portal D 2002 J.Phys.:Condens.Matter14 2745
[27]Perdew J P,Wang Y 1992 Phys.Rev.B 46 12947
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[29]Yao K,Fu H 2012 Appl.Phys.Lett.100 13502
[30]Wang B G,Wang J,Gou H 2001 J.Phys.Soc.Jpn.70 2645
[31]Rejec T,Ramsak A,Jefferson J H 2002 Phys.Rev.B 65235301
[32]Broido D A,Mingo N 2005 Phys.Rev.Lett.95 096105
[33]Saha K K,Markussen T,Thygesen K S,Nikolic B K 2011Phys.Rev.B 84 041412(R)
[34]Du A,Chen Y,Zhu Z,Lu G,Smith S C 2009 J.Am.Chem.Soc.131 1682
[35]Dutta S,Manna A,Pati S 2009 Phys.Rev.Lett.102 096601
[36]He J,Chen K Q,Fan Z Q,Tang L M,Hu W P 2010 Appl.Phys.Lett.97 193305
[37]Tang S,Cao Z 2010 Phys.Chem.Chem.Phys.12 2313
[38]Yu Z,Hu M L,Zhang C X,He C Y,Sun L Z,Zhong J 2011J.Phys.Chem.C 115 10836
[39]Liu Y,Wu X,Zhao Y,Zeng X C,Yang J 2011 J.Phys.Chem.C 115 9442
[40]Wang Y,Ding Y,Ni J 2012 J.Phys.Chem.C 116 5995
[41]Tang C,Kou L,Chen C 2012 Chem.Phys.Lett.523 98
[42]Christenholz C L,Obenchain D A,Peebles R A,Peebles S A2014 J.Phys.Chem.C 118 16104
[43]WangY,Li Y,Chen Z 2014 J.Phys.Chem.C 118 25051
[44]Zhu L,Li R,Yao K L 2017 Phys.Chem.Chem.Phys.194085