Computational Solid State Physics 計算物性学特論

1. Computational Solid State Physics計算物性学特論 Purpose To understand fundamental solid state physics in nanostructures with computer simulation 計算機シミュレーションを用いて、ナノスケール原子構造の物性の基礎を理解する。 Akiko Natori 名取　晃子

2. Nanotechnology for electronics • How to make nanometer-scale structure? • What featuresof electronic properties are expected in nanometer-scale structure? • How to use the electronic properties for creating novel devices?

3. Study • Atomic structure: Interaction between atoms Homogeneous structure: Gas, liquid and solid Solid: crystal, quasi-crystal and amorphous Heterogeneous structure: growth mode of thin films, quantum well, superlattice • Electronic properties in nanometer-scale structure: Electronic structure Transport properties

4. Recommended textbooks • The physics of low-dimensional semiconductors, J.H. Davies, Cambridge University press • Mesoscopic electronics in solid state nanostructures, T.Heinzel, WILEY-VCH • Physics and applications of semiconductor microstructures, M.Jaros, Oxford Science Publications • Simulation for solid state physics, R.H.Silsbee and J.Drager, Cambridge University press

5. Acknowledgements My students, M. Hirayama, J. Ito, H. Masu and S. Wakui, helped to shape this e-Learning text. I am grateful for their help. I would also like to thank Prof. K. Natori in Tsukuba University for permitting me to use CASTEP. It is a pleasure to thank Prof. T. Okamoto and Prof. K. Nakayama in The University of Electro-Communications for giving me a chance and various convenience to make e-Learning text.

6. 1. Introduction: What is nanotechnology? 2. Interactions between atoms and the lattice properties of crystals 3. Covalent bond and morphology of crystals, surfaces and interfaces 4. Electronic structure of crystals 5. Band offsets at hetero-interfaces and effective mass approximation 6. Pseudopotential 7. Many-body effect I: Hartree approximation, Hartree-Fock approximation and density functional method 8. Many-body effect II: Quantum Monte Carlo method 9. Transport properties I: Diffusive transport 10.Transport properties II: Ballistic transport A1. Solutions A2. Electronic properties of crystals: Calculation results by CASTEP A3.Simulation for solid state physics CONTENTS

7. Computational Solid State Physics 計算物性学特論　第１回 1. Introduction What is nonotechnology?

8. What is nano? • 10-3 : m (Milli) • 10-6 : μ (Maicro) 微 （び） • 10-9 : n (Nano)　 　塵　 （じん） • 10-12 : p (Pico) 　　 漠　 （ばく） • 10-15 : f (Femto)　 須臾　（しゅゆ） • 10-18 : a (Atto)　 　刹那 （せつな） • 10-21 : 　 清浄 （せいじょう）

9. What is nanotechnology? Nanometer scale control of materials which requires to manipulate atoms and molecules. 1nm=10-9m Size of atoms：　a spread of electron cloud0.1nm structure control in atomic scale： Top-down method、bottom-up method

10. Expected effects for electrons in nanostructures • Quantum confinement effect • Charge discreteness and strong electron-electron Coulomb interaction effects • Tunneling effects • Strong electric field effects • Ballistic transport effects

11. Application fields of nanotechnology

12. Miniaturization of electron devices • High integration • High speed • Low consumption electric power • Low cost Miniaturization by top-down method

13. 1950 1970 1980 2000 Application to electronic devices Ge transistor Quantum corral Carbon nanotube Point contact LSI L.L.Sohn, Nature 394(1998)131

14. Roadmap for Si MicroelectronicsMoor’s Low: M.Schulz, Nature 399(1999)729

15. Moor’s law and number of electrons per device Moor’sLaw: Device size 2/3, Chip size 1.5, Integration 4-times / new chip（3 years）

16. I-V Charactaristics of resonant-tunneling diodes

17. Resonant tunneling diode resonant tunneling quasi-bound state Fermi sea of electrons Profile through a three-dimensional resonant-tunneling diode.

18. Quantum point contact GaAs/AlGaAsinterface : two-dimensional electron gas Quantum conductance

19. Conductance of a quantum point contact

20. ・Electrons are wave with wave vector ・Interference stripe with STM images of electron flow close to a quantum point contact

21. [110] gold contact TEM image

22. Quantized conductance atomic switch(QCAS) Nature, 433(’05)47

23. Switching results of the QCAS

24. Quantum conductance of QCAS

25. Si single-electron CCD Electron device using Coulomb blockade caused by electron-electron Coulomb interaction SEM image

26. Manipulation of elementary charge

27. Sensing of a single hole

28. Kondo corral STM image Bottom-up method Interference pattern of two-dimensional electron gas on Co/Cu(111) D.M.Eigler et al. PRL 86(2001)2392

29. Molecualr abacus STM image of molecules

30. Quantum computer Computer which uses principles of “superposition” in quantum mechanics Classical bit：　 １　or 0 Quantum bit： superposition of 0 and 1 N qubit： express 2n states simultaneously Examples of qubit：　electron spin, nuclear spin

31. Quantum computer by Kane’s model STM image Qubit: Nuclear spin of 31P in Si

32. T.Yamamoto et al. Nature 425 (2003) Controlled not gate qubit:superconducting Cooper pairs SEM image

33. Spin coupling in a double-dots Qubit: electron spin in a dot TEM image