正常金属-分子量子点-超导耦合系统的介观输运
|
摘要
运用非平衡格林函数理论、正则变换以及BCS平均场理论研究了正常金属-分子量子点-超导耦合系统(N-MQD-S)的介观输运,得到了系统的电流公式并选择适当的参数进行了数值计算.数值计算结果表明:电声子耦合强度λ与线宽函数Γ对系统的输运行为有较大影响.当λ增大时,由声子辅助隧穿所产生的共振峰将高于分子量子点自身能级产生的共振峰;当线宽函数Γ增大时,在Andreev反射共振峰的两侧将出现新的边峰.
We have investigated the mesoscopic transport through the normal metal-molecule quantum dot-superconductor(N -MQD-S)system by using nonequilibrium Green's function and canonical transformation of the electron-phonon interaction.We employ BCS theory to describe the Hamiltonian of the superconducting lead.The coupling strength A of electron-phonon interaction(EP1)has huge influence on the current.As the A increases,the peak caused by the phonon-assisted transport is higher than the main peak.This is different from N-MQD -N system.We also find that the linewidth function Γ affect the transport properties of the system.As the F increases,side peaks emerge around the peak caused by Andreev reflection.
We have investigated the mesoscopic transport through the normal metal-molecule quantum dot-superconductor(N -MQD-S)system by using nonequilibrium Green's function and canonical transformation of the electron-phonon interaction.We employ BCS theory to describe the Hamiltonian of the superconducting lead.The coupling strength A of electron-phonon interaction(EP1)has huge influence on the current.As the A increases,the peak caused by the phonon-assisted transport is higher than the main peak.This is different from N-MQD -N system.We also find that the linewidth function Γ affect the transport properties of the system.As the F increases,side peaks emerge around the peak caused by Andreev reflection.
引文
[1] Park H.A mesoscale phytoplankton bloom in the polar Southern Ocean stimulated iron fertilization[J].Nature,2000,407:57;Park J.Coulomb blockade and the Kondo effect in single-atom transistors[J].Nature,2002,417:722
[2] Reichert J,et al.Driving current through single organic molecules[J].Phys.Rev.Lett.,2002,88:176804
[3] Liang W,et al.Kondo resonance in a single-molecule transistor[J].Nature,2002,417:725．
[4] Reed M A,et al.Conductance of a molecular junction[J].Science,1997,278:252
[5] Tsukagoshi K,Alphenaar B W,Ago H.Coherent transport of electron spin in a ferromagnetically contacted carbon nanotube[J].Nature,1999,401:572
[6] Petta J R,Slater S K,D.C.Spin-dependent transport in molecular tunnel junctions[J].Phys.Rev.Lett.,2004,93:136601
[7] Zhang L Y,Wang C Y,Wei Y G,et al.Spin-polarized electron transport through nanometer-scale Al grains[J].Phys.Rev.B,2005,72:155445
[8] Chen J,Reed M A,Rawlett A M,et al.Large onoff ratios and negative differential resistance in a molecular electronic device[J].Science,1999,286:155
[9] McCarthy K D,et al.Incoherent dynamics of vibrating single-molecule transistors[J].Phys.Rev.B,2003,67:245415
[10] Mitra A,Aleiner I,Millis A J.Phonon effects in molecular transistors:quantal and classical treatment[J].Phys.Rev.B,2004,69:245302
[11] Wingreen N S,Jacobsen,K.W J,Wilkins W.Inelastic scattering in resonant tunneling[J].Phys.Rev.B,1989,40:11834
[12] Yang K H,Liu C Z,Wu Y P.Influence of strength of electron-phonon coupling on shot noise in a quantum dot system.[J].J.At.Mol.Phys.(原子与分子物理学报),2009,26(3) :585
[13] Cornaglia P S,Ness H,Grempel R.Many-body effects on the transport properties of single-molecule devices[J].Phys.Rev.Lett.,2004,93:147201
[14] Cornaglia P S,Grempel D R.Magnetoconductance through a vibrating molecule in the Kondo regime[J].Phys.Rev.B,2003,71:245326
[15] Sun Q F,Wang J,Lin T H.Resonant Andreev reflection in a normal-metal-quantum-dot-superconductor system[J].Phys.Rev.B,1999,59:3831
[16] Sun Q F,Wang J,Lin T H.Photon-assisted Andreev tunneling through a mesoscopic hybrid system[J].Phys.Rev.B,1999,59:13126
[17] Zhao H K,Gehlen G V.Mesoscopic transport through a normal-metal-quantum-dot-superconductor system with ac responses[J].Phys.Rev.B,1998,58:13660
[18] Zhao H K,Wang J.Zeeman-split mesoscopic transport through a normal-metal-quant-um-dot-superconductor system with ac response[J].Phys.Rev.B,2001,64:094505
[19] Chen Z Z,Lu R,Zhu B F.Effects of electron-phonon interaction on nonequilibrium transport through a single-molecule transistor[J].Phys.Rev.B,2005,71:165324
[20] Jauho A P.Wingreen N S,Meir Y.Time-dependent transport in interacting and noninteracting resonant-tunneling systems[J].Phys.Rev.B,1994,50:5528
[21] Zhang P,Li Y X.Andreev reflection and shot noise in a quantum dot with phonon modes[J].J.Phys.:Condens.Matter,2009,21:095602
[2] Reichert J,et al.Driving current through single organic molecules[J].Phys.Rev.Lett.,2002,88:176804
[3] Liang W,et al.Kondo resonance in a single-molecule transistor[J].Nature,2002,417:725．
[4] Reed M A,et al.Conductance of a molecular junction[J].Science,1997,278:252
[5] Tsukagoshi K,Alphenaar B W,Ago H.Coherent transport of electron spin in a ferromagnetically contacted carbon nanotube[J].Nature,1999,401:572
[6] Petta J R,Slater S K,D.C.Spin-dependent transport in molecular tunnel junctions[J].Phys.Rev.Lett.,2004,93:136601
[7] Zhang L Y,Wang C Y,Wei Y G,et al.Spin-polarized electron transport through nanometer-scale Al grains[J].Phys.Rev.B,2005,72:155445
[8] Chen J,Reed M A,Rawlett A M,et al.Large onoff ratios and negative differential resistance in a molecular electronic device[J].Science,1999,286:155
[9] McCarthy K D,et al.Incoherent dynamics of vibrating single-molecule transistors[J].Phys.Rev.B,2003,67:245415
[10] Mitra A,Aleiner I,Millis A J.Phonon effects in molecular transistors:quantal and classical treatment[J].Phys.Rev.B,2004,69:245302
[11] Wingreen N S,Jacobsen,K.W J,Wilkins W.Inelastic scattering in resonant tunneling[J].Phys.Rev.B,1989,40:11834
[12] Yang K H,Liu C Z,Wu Y P.Influence of strength of electron-phonon coupling on shot noise in a quantum dot system.[J].J.At.Mol.Phys.(原子与分子物理学报),2009,26(3) :585
[13] Cornaglia P S,Ness H,Grempel R.Many-body effects on the transport properties of single-molecule devices[J].Phys.Rev.Lett.,2004,93:147201
[14] Cornaglia P S,Grempel D R.Magnetoconductance through a vibrating molecule in the Kondo regime[J].Phys.Rev.B,2003,71:245326
[15] Sun Q F,Wang J,Lin T H.Resonant Andreev reflection in a normal-metal-quantum-dot-superconductor system[J].Phys.Rev.B,1999,59:3831
[16] Sun Q F,Wang J,Lin T H.Photon-assisted Andreev tunneling through a mesoscopic hybrid system[J].Phys.Rev.B,1999,59:13126
[17] Zhao H K,Gehlen G V.Mesoscopic transport through a normal-metal-quantum-dot-superconductor system with ac responses[J].Phys.Rev.B,1998,58:13660
[18] Zhao H K,Wang J.Zeeman-split mesoscopic transport through a normal-metal-quant-um-dot-superconductor system with ac response[J].Phys.Rev.B,2001,64:094505
[19] Chen Z Z,Lu R,Zhu B F.Effects of electron-phonon interaction on nonequilibrium transport through a single-molecule transistor[J].Phys.Rev.B,2005,71:165324
[20] Jauho A P.Wingreen N S,Meir Y.Time-dependent transport in interacting and noninteracting resonant-tunneling systems[J].Phys.Rev.B,1994,50:5528
[21] Zhang P,Li Y X.Andreev reflection and shot noise in a quantum dot with phonon modes[J].J.Phys.:Condens.Matter,2009,21:095602