Lecture 09

Lecture 09 - EEE 434/591Quantum Mechanics L9:1 Tunneling...

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EEE 434 Quantum Mechanics http://www.eas.asu.edu/~ferry/EEE434.htm L9:1 EEE 434/591—Quantum Mechanics David K. Ferry Regents’ Professor Arizona State University Tunneling microscope
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EEE 434 Quantum Mechanics http://www.eas.asu.edu/~ferry/EEE434.htm L9:2 Tunneling Classically: A particle will bounce off the wall and be reflected Quantum mechanically: part of the wave will “tunnel” through just as a wave goes through a dielectric interface.
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EEE 434 Quantum Mechanics http://www.eas.asu.edu/~ferry/EEE434.htm L9:3
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EEE 434 Quantum Mechanics http://www.eas.asu.edu/~ferry/EEE434.htm L9:4 Tunneling arises when we think about the particle as being a wave. That is, there is a classical phenomenon in optics known as total internal reflection. We see this in the swimming pool, where there is a critical angle beyond which we cannot see out of the water. This angle is given by the difference between the dielectric constant in water and that in air. However, there is an evanescent wave, and if we are close enough, we can couple to another high dielectric constant medium. This process is known as frustrated total internal reflection.
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EEE 434 Quantum Mechanics http://www.eas.asu.edu/~ferry/EEE434.htm L9:5 There is total internal reflection of this light in this media, yet … we see some light coming out the back side.
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EEE 434 Quantum Mechanics http://www.eas.asu.edu/~ferry/EEE434.htm L9:6 The evanescent wave decays exponentially.
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EEE 434 Quantum Mechanics http://www.eas.asu.edu/~ferry/EEE434.htm L9:7 In fact, we can use the evanescent wave to couple into another propagating media, such as a surface wave shown here.
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http://www.eas.asu.edu/~ferry/EEE434.htm L9:8 This makes for wave couplers in optical fibers. How does this appear for quantum waves?
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This note was uploaded on 10/03/2010 for the course EEE 434 taught by Professor Roedel during the Fall '08 term at ASU.

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Lecture 09 - EEE 434/591Quantum Mechanics L9:1 Tunneling...

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