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Department of Electronics

Nanoelectronics 03. Atsufumi Hirohata. Department of Electronics. 17:00 17/January/2014 Friday (P/L 001). Quick Review over the Last Lecture. ( Electric ) field. ( Magnetic ) field. Propagation direction. Maxwell equations :.

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Department of Electronics

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  1. Nanoelectronics 03 Atsufumi Hirohata Department of Electronics 17:00 17/January/2014 Friday (P/L 001)

  2. Quick Review over the Last Lecture ( Electric ) field ( Magnetic ) field Propagation direction Maxwell equations :  Time-independent case : ( Ampère’s / Biot-Savart ) law  ( Faraday’s ) law of induction ( Time-dependent equations )  ( Gauss ) law ( Initial conditions )  ( Gauss ) law for magnetism ( Assumptions ) Electromagnetic wave : propagation speed : in a vacuum,

  3. Contents of Nanoelectronics I. Introduction to Nanoelectronics (01) 01 Micro- or nano-electronics ? II. Electromagnetism (02 & 03) 02 Maxwell equations 03 Scalar and vector potentials III. Basics of quantum mechanics (04 ~ 06) IV. Applications of quantum mechanics (07, 10, 11, 13 & 14) V. Nanodevices (08, 09, 12, 15 ~ 18)

  4. 03 Scalar and Vector Potentials • Scalar potential  • Vector potential A • Lorentz transformation

  5. Maxwell Equations Maxwell equations : E : electric field, B : magnetic flux density, H : magnetic field, D : electric flux density, J : current density and  : charge density Supplemental equations for materials :  Definition of an electric flux density  Definition of an magnetic flux density  Ohm’s law

  6. Electromagnetic Potentials Scalar potential  and vector potential A are defined as (1) (2) By substituting these equations into Eq. (2), (3) (4) Here,  Similarly, y- and z-components become 0. Also,  Satisfies Eq. (2).

  7. Electromagnetic Potentials (Cont'd) (1) (2) By substituting these equations into Eq. (4), (3) (4)  Satisfies Eq. (4).

  8. Electromagnetic Potentials (Cont'd) By assuming x as a differentiable function, we define  Gauge transformation Here, A’ and ’ provide E and B as the same as A and . Therefore, electromagnetic potentials A and  contains uncertainty of x. In particular, when A and  satisfies the following condition :  Laurentz gauge Under this condition, Eqs. (1) and (3) are expressed as (1) (2) (3)  Equation solving at home (4)

  9. Einstein's Theory of Relativity In 1905, Albert Einstein proposed the theory of special relativity : Lorentz invariance for Maxwell’s equations (1900) Poincaré proved the Lorentz invariance for dynamics.  Lorentz invariance in any inertial coordinates Speed of light (electromagnetic wave) is constant. * http://www.wikipedia.org/

  10. Scalar Potential  Scholar potential holds the following relationship with a force : The concept was first introduced by Joseph-Louis Lagrange in 1773, and named as scalar potential by George Green in 1828. * http://www12.plala.or.jp/ksp/vectoranalysis/ScalarPotential/ ** http://www.wikipedia.org/

  11. Scalar Potential  and Vector Potential A Scalar potential holds the following relationship with a force : Electrical current Voltage potential induced by a positive charge Vector potential around a current rot A Magnetic field Vector potential A (decrease with increasing the distance from the current) Electric field E (induced along the direction to decrease the voltage potential) Magnetic field H (induced along the axis of the rotational flux of the vector potential, rot A) * http://www.phys.u-ryukyu.ac.jp/~maeno/cgi-bin/pukiwiki/index.php

  12. Vector Potential A Faraday found electromagnetic induction in 1831 : Faraday considered that an “electronic state” of the coil can be modified by moving a magnet.  induces current flow. In 1856, Maxwell proposed a theory with using a vector potential instead of “electronic state.”  Rotational spatial distribution of A generates a magnetic flux B.  Time evolution of A generates an electric field E. * http://www.physics.uiowa.edu/~umallik/adventure/nov_06-04.html

  13. Maxwell's Vector Potential magnetic line of force vector potential magnetic field electrical current electrical current • By the rotation of the vector potentials in the opposite directions, rollers between the vector potentials move towards one direction.  Ampère’s law After the observation of a electromagnetic wave, E and B : physical quantities A : mathematical variable * http://www.ieice.org/jpn/books/kaishikiji/200012/20001201-2.html

  14. Aharonov-Bohm Effect electron source coil shield phase shift magnetic field interference Yakir Aharonov and David Bohm theoretically predicted in 1959 : Electron can modify its phase without any electrical / magnetic fields. * http://www.wikipedia.org/; http://www.physics.sc.edu/~quantum/People/Yakir_Aharonov/yakir_aharonov.html ** http://www.ieice.org/jpn/books/kaishikiji/200012/20001201-3.html

  15. Observation of the Vector Potential Nb NiFe In 1982, Akira Tonomura proved the Aharonov-Bohm effect : No phase shift Phase shift = wavelength / 2 * http://www.nanonet.go.jp/japanese/mailmag/2003/009a.html ** http://www.ieice. org/jpn/books/kaishikiji/200012/20001201-4.html

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