Table Of ContentElectron Transport in Nanosystems
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Series B: Physics and Biophysics
Electron Transport in Nanosystems
Edited by
Janez Bonca
J. Stefan Institute,
Ljubljana, Slovenia
and
Sergei Kruchinin
Bogolyubov Institute for Theoretical Physics,
Kiev, Ukraine
123
Published in cooperation with NATO Public Diplomacy Division
ˆ
Proceedings of the NATO Advanced Research Workshop on
Electron Transport in Nanosystems
Yalta, Ukraine
17–21 September 2007
Library of Congress Control Number: 2008936556
ISBN 978-1-4020-9145-2 (PB)
ISBN 978-1-4020-9144-5 (HB)
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PREFACE
These proceedings of the NATO-ARW “Electron transport in nanosystems”
held at the “Russia” Hotel, Yalta, Ukraine from 17–21 September 2007
resulted in many discussions between various speakers.
The wide range of topics discussed at the Yalta NATO meeting included
the new nanodevice applications, novel materials, superconductivity and sen-
sors. There have been many significant advances in the past 2 years and some
entirely new directions of research in these fields are just opening up. Recent
advances in nanoscience have demonstrated that fundamentally new physi-
cal phenomena are found when systems are reduced in size with dimensions,
comparable to the fundamental microscopic length scales of the investigated
material. Late developments in nanotechnology and measurement techniques
now allow experimental investigation of transport properties of nanodevices.
Great interest in this research is focused on development of spintronics,
molecular electronics and quantum information processing and graphene. At
the workshop, important open problems concerning cuprate superconductity,
mesoscopic superconductors and novel superconductors such MgB2, CeCoIn5
where considered. There was much discussion of the mechanism and symmetry
of pairing for cuprate superconductors as well as the nature of the pseudogap.
In the session on novel superconductors, the physical properties of MgB2 were
discussed. There were also lively debates about two-gap superconductivity in
MgB2.
We would like to thank the NATO Science Committee for the essential
financial support, without which the meeting could not have taken place. We
also acknowledge the National Academy of Science of Ukraine, Ministry of
Ukraine for Education and Science, J. Stefan Institute, Ljubljana, Slovenia
and Faculty of Mathematics and Physics, University of Ljubljana, Slovenia
for their generous support.
Ljubljana, Kiev, Janez Bonˇca
June 2008 Sergei Kruchinin
CONTENTS
Part I Electron transport in nanodevices
1 Optical properties and electronic structure
of organic-inorganic nano-interface
A. Fujiwara, A. Konishi, and E. Shikoh . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
1.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
1.1.1 Organic field effect transistor . . . . . . . . . . . . . . . . . . . . . . . . . 4
1.1.2 Interface effects on organic field effect transistor . . . . . . . . 5
1.2 Experimental details . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
1.2.1 Sample structure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
1.2.2 Experimental procedure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
1.3 Results and discussion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
1.3.1 Interface between C60 and Au . . . . . . . . . . . . . . . . . . . . . . . . 8
1.3.2 Interface between C60 and ITO . . . . . . . . . . . . . . . . . . . . . . . 10
1.4 Conclusion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13
2 Electron transport in nanowires – an engineer’s view
W. Nawrocki . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17
2.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17
2.2 Ballistic electron transport . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18
2.3 Electrical conductance measurements . . . . . . . . . . . . . . . . . . . . . . . . . 21
2.4 Measurement results on electrical conductance in metallic
nanowires . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22
2.5 Thermal problems in nanowires . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23
References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25
VIII Contents
3 Nanoporous anodic alumina wire templates
for nanowire devices
T.L. Wade, A.A. Abdulla, M.C. Ciornei, D. Pribat, C. Cojocaru,
and J.-E. Wegrowe . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27
3.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27
3.2 Background . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28
3.3 Experimental . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31
3.4 Results . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32
3.5 Conclusion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33
References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33
4 Friedel oscillations in nanowires at finite bias voltage
A. Gorczyca, M. Ma´ska, and M. Mierzejewski . . . . . . . . . . . . . . . . . . . . . . 37
4.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 37
4.2 Model . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 38
4.3 Results and discussion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 39
References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 46
5 Spin orbit interaction induced spin-separation
in platinum nanostructure
Koong Chee Wen, N. Chandrasekhar, C. Miniatura,
and Berthold-Georg Englert . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 49
5.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 49
5.2 Spin-orbit interaction and its effect on electron spin . . . . . . . . . . . . 50
5.3 Experimental procedure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 52
5.4 Results and discussion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 54
5.5 Conclusion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 56
References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 57
6 The problem of true macroscopic charge quantization
in the coulomb blockade
I.S. Burmistrov and A.M.M. Pruisken . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 59
6.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 59
6.2 AES model . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 61
6.3 Kubo formulae for the observable parameters . . . . . . . . . . . . . . . . . . 62
′
6.4 Weak coupling regime, g ≫ 1 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 63
′
6.5 Strong coupling regime, g ≪ 1 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 64
6.6 Summary and conclusions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 66
References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 67
Contents IX
Part II Superconductivity
7 High-field flux dynamics in disordered two-band
superconductivity
J.M. Knight and M.N. Kunchur . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 71
7.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 71
7.2 Electric field penetration depth . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 72
7.3 Viscous drag coefficient . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 74
7.4 Parameters . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 75
7.5 Discussion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 76
References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 77
8 Superconductivity in the quantum-size regime
A.A. Shanenko, M.D. Croitoru, and F.M. Peeters . . . . . . . . . . . . . . . . . . . 79
8.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 79
8.2 Bogoliubov-de Gennes equations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 81
8.3 Quantum-size oscillations and resonances . . . . . . . . . . . . . . . . . . . . . 83
8.4 Superconducting nanofilms in the quantum-size regime . . . . . . . . . 85
8.5 Superconducting nanowires in the quantum-size regime . . . . . . . . . 91
8.6 New Andreev-type states induced by quantum confinement . . . . . 95
8.7 Superconducting-to-normal transition induced
by a magnetic field . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 98
8.8 Conclusion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 101
References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 102
9 Kondo effect coupled to superconductivity in ultrasmall
grains
H. Nagao and S.P. Kruchinin . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 105
9.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 105
9.2 Kondo regime coupled to superconductivity . . . . . . . . . . . . . . . . . . . 106
9.2.1 Model . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 107
9.2.2 Mean field approximation . . . . . . . . . . . . . . . . . . . . . . . . . . . . 108
9.3 Discussion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 108
9.3.1 Critical level spacing in Kondo effect . . . . . . . . . . . . . . . . . . 109
9.3.2 Kondo effect coupled to superconductivity . . . . . . . . . . . . . 110
9.3.3 Exact solution for kondo regime . . . . . . . . . . . . . . . . . . . . . . 111
9.4 Concluding remarks . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 112
References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 114
10 Emerging measurement techniques
for studies of mesoscopic superconductors
A. Rydh, S. Tagliati, R.A. Nilsson, R. Xie, J.E. Pearson,
U. Welp, W.-K. Kwok, and R. Divan . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 117
10.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 117
10.2 Traditional techniques review . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 118
X Contents
10.2.1 Four-point probes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 118
10.2.2 Bridges . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 119
10.2.3 Lock-in amplifiers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 119
10.3 Differential Micro Calorimetry . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 120
10.3.1 Technique overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 120
10.3.2 Device construction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 121
10.3.3 Measurement example . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 121
10.4 Synchronization of FPGA-based lock-in amplifiers . . . . . . . . . . . . . 123
10.4.1 Technique overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 123
10.4.2 Measurement example . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 124
10.5 Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 125
References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 125
11 Interplay of magnetism and superconductivity
in CeCoIn5
R. Movshovich, Y. Tokiwa, F. Ronning, A. Bianchi, C. Capan,
B.L. Young, R.R. Urbano, N.J. Curro, T. Park, J.D. Thompson,
E. Bauer, and J.L. Sarrao . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 127
11.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 127
11.2 Magnetism in CeCoIn5 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 132
11.3 CeRhIn5 under pressure: Close relative to CeCoIn5 . . . . . . . . . . . . . 134
11.4 HFLT phase and magnetism in CeCoIn5 under pressure . . . . . . . . 136
11.5 Conclusions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 137
References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 137
12 Bipolaronic Proximity and Other Unconventional
Effects in Cuprate Superconductors
A.S. Alexandrov . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 139
12.1 Polarons in high-temperature superconductors . . . . . . . . . . . . . . . . . 139
12.2 Unconventional proximity effects . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 141
12.3 Quantum magneto-oscillations, d-wave symmetry
and checkerboard modulations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 145
12.4 Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 150
References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 151
13 Interlayer tunneling in stacked junctions of high
temperature superconductors, CDW materials
and graphite
Yu.I. Latyshev . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 155
13.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 155
13.2 Interlayer tunneling in HTS materials . . . . . . . . . . . . . . . . . . . . . . . . 156
13.3 Interlayer tunneling in the CDW state . . . . . . . . . . . . . . . . . . . . . . . . 160
13.4 Fabrication of the stacked nanostructures . . . . . . . . . . . . . . . . . . . . . 161
13.5 CDW gap features on interlayer tunneling spectra of NbSe3 . . . . . 163
13.6 The intragap states in NbSe3 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 166
13.7 Amplitude solitons in o-TaS3 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 168
