ballistic conductance of suspended nanowires: an ab initio description admol dresden, 23.-27.02.2004...

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


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


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


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


Local partial DOS at central Cu atom

G = 2.59 G0CuCu

fcc

[100

]fc

c [1

00]

Conductance of Cu wires


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


Even-odd parity effect in the density of states

s-LDOS p-LDOS


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)


M. Czerner, diploma thesis, MLU Halle (2003)

spsp impurity impurity(Z = 11 ... 16)(Z = 11 ... 16)

Conductance through sp-atoms


Conductance through sp-atoms


spsp impurity impurity(Z = 11 ... 16)(Z = 11 ... 16)

Conductance through 3d transition metal atoms

3d3d impurity impurity(Z = 21 ... 30)(Z = 21 ... 30)


Conductance through 3d transition metal atoms


Conductance of Co wires


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)


Ballistic Magnetoconductance of Co wires


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 %


ballistic conductance of suspended nanowires: an ab initio description admol dresden, 23.-27.02.2004...

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