Ballistic conductance of suspended nanowires: An ab initio description
description
Transcript of Ballistic conductance of suspended nanowires: An ab initio description
Ballistic conductance of suspended nanowires: An ab initio description
ADMOL Dresden , 23.-27.02.2004
M. Czerner1, A. Bagrets1, N. Papanikolaou2, V.S. Stepanyuk3 and I. Mertig1
1Martin-Luther-Universität Halle, Germany2Institute of Material Science, National Center for Scientific Research „Demokritos“,
Athens, Greece3 Max-Planck-Institute Mikrostrukturphysik Halle, Germany
Content
• Motivation
• Method
• Parity oscillations
• Relaxation and conductance
• Impurity scattering
• Ballistic magnetoconductance
• Summary
ADMOL Dresden , 23.-27.02.2004
KKR-Workshop 2004 München, 13.-15.02.2004
Motivation
H. Ohnishi, Yu. Kondo, K. Takayanagi, Nature 395, 780 (1998)
Metallic Nanowires
Conductance
KKR Green‘s function method
Semi-infinite leads Suspended nanowire
ADMOL Dresden , 23.-27.02.2004
Landauer theory with Green‘s functions
Matrix elements
H.U. Baranger and A.D. Stone, Phys. Rev. B 40, 8169 (1989)
1 Sample 2
Conductance
Landauer formula
ADMOL Dresden , 23.-27.02.2004
Conductance of Cu wires
Conductance histogram at T=4.2K for Cu, A. I. Yanson, PhD. Thesis, Leiden University, the Netherlands, 2001.
CuCu
fcc
[100
]fc
c [1
00]
G = 1.10 G0
Local partial DOS at central Cu atom
ADMOL Dresden , 23.-27.02.2004
Local partial DOS at central Cu atom
G = 2.59 G0CuCu
fcc
[100
]fc
c [1
00]
Conductance of Cu wires
ADMOL Dresden , 23.-27.02.2004
Conductance histogram at T=4.2K for Cu, A. I. Yanson, PhD. Thesis, Leiden University, the Netherlands, 2001.
Parity oscillation in the conductance of Cu wires
KKR calculation
M. Czerner, diploma thesis, MLU Halle (2003)R.H.M. Smit et al., Phys. Rev. Lett. 91,
076805-1 (2003)
Experiment
ADMOL Dresden , 23.-27.02.2004
Even-odd parity effect in the density of states
s-LDOS p-LDOS
ADMOL Dresden , 23.-27.02.2004
Stress and conductance in a Cu wire
11 12 13 14 15
-0.6
-0.4
-0.2
0.0
0.2
0.4
0.6
Ave
rage
str
ess
per
Cu
ato
m (
ev/Å
³)
Distance d (Å)
a
b
c
Averaged stress Conductance
V.S.Stepanyuk et al., Phys. Rev. B (2003)
ADMOL Dresden , 23.-27.02.2004
M. Czerner, diploma thesis, MLU Halle (2003)
spsp impurity impurity(Z = 11 ... 16)(Z = 11 ... 16)
Conductance through sp-atoms
ADMOL Dresden , 23.-27.02.2004
Conductance through sp-atoms
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spsp impurity impurity(Z = 11 ... 16)(Z = 11 ... 16)
Conductance through sp-atoms
ADMOL Dresden , 23.-27.02.2004
spsp impurity impurity(Z = 11 ... 16)(Z = 11 ... 16)
Conductance through 3d transition metal atoms
3d3d impurity impurity(Z = 21 ... 30)(Z = 21 ... 30)
ADMOL Dresden , 23.-27.02.2004
Conductance through 3d transition metal atoms
3d3d impurity impurity(Z = 21 ... 30)(Z = 21 ... 30)
ADMOL Dresden , 23.-27.02.2004
Conductance through 3d transition metal atoms
3d3d impurity impurity(Z = 21 ... 30)(Z = 21 ... 30)
ADMOL Dresden , 23.-27.02.2004
Conductance through 3d transition metal atoms
3d3d impurity impurity(Z = 21 ... 30)(Z = 21 ... 30)
ADMOL Dresden , 23.-27.02.2004
Conductance through 3d transition metal atoms
ADMOL Dresden , 23.-27.02.2004
Conductance through 3d transition metal atoms
ADMOL Dresden , 23.-27.02.2004
Conductance through 3d transition metal atoms
ADMOL Dresden , 23.-27.02.2004
Conductance of Co wires
ADMOL Dresden , 23.-27.02.2004
DOS Conductance
Ballistic Magnetoconductance
Parallel configuration (P)
MR =(gP – gAP)/gAP x 100%
linear zig-zag
Co 29 38 Cu 16 18 Al 49 19 Si 50 21
Antiparallel configuration (AP)
ADMOL Dresden , 23.-27.02.2004
Ballistic Magnetoconductance of Co wires
ADMOL Dresden , 23.-27.02.2004
MR = 38 % MR = 29 %
Summary
I. Conductance depends strongly on geometry of the junction
II. Parity oscillations
III. Relaxation enhances conductance
III. Impurity scattering modulates conductance
IV. Ballistic magnetoconductance is ~50 %
ADMOL Dresden , 23.-27.02.2004