Playing pool with electrons

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Playing pool with electrons
www.tallpoppies.net.au
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What is an electron?

• Electrons are the tiny negatively charged
  particles that orbit the nucleus in atoms.

• The electricity that comes out of your wall
  socket at home is basically a flow of these
  electrons, just like the water that comes out of
  your tap at home is a flow of water molecules.

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Kill your computer (or playstation)!
? 50 million

• If you smash your computer, somewhere inside you
  will find 50 million or so transistors on a
  silicon chip

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The transistor is just a tap for electrons
Interesting fact the 1s and 0s that represent
data in your computer are just the on and off
states of the transistors in the computer chips.
Gate
Gate
Insulator (oxide)
n-Si
p-typesilicon substrate

• The voltage applied to the gate allows control of
  the current flowing in the channel.

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Progress in electronics

• The number of transistors on a computer chip
  doubles roughly every 18 months, until

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The same development happens for video games

• Everyone knows computers were really made for
  video games!

• This development even holds for video games, both
  for CPU and memory.

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Fancy a snack?
Video www.youtube.com
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Computers are getting too hot

• The current generation of computers really do
  produce enough heat to fry an egg!

• The heat problem has brought the usual speed
  increases to a grinding halt ? Core 2 Duo, etc.

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Where does the heat come from?
Interesting fact the 1s and 0s that represent
data in your computer are just the on and off
states of the transistors in the computer chips.
Gate
Gate
Insulator (oxide)
n-Si
p-typesilicon substrate

• The voltage applied to the gate allows control of
  the current flowing in the channel.

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Two Solutions
Better cooling, but it will only take you so far,
and it doesnt help for laptops, etc.
We find a new way to do computing that doesnt
involve so much heat ?spintronics.
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How can we do this?
One way to make spintronics is to use magnetic
materials, but this doesnt work well when you
want to put lots of tiny devices close together
(imagine putting two fridge magnets together).

-
Another trick is to use a special property of
some materials that makes the different spins
bounce off walls in different ways in a sense,
we make a transistor that is basically a tiny
pool table!
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What my research is about

• Were now reaching the point where transistors
  are becoming so small that the quantum mechanical
  properties of the electron become very important.
  Some strange things can happen when this occurs,
  but you might also be able to do some really
  useful things too!

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How to make a real pool table

• There are some things well need to make an
  electron pool table

1. You need a flat table for the balls to roll on.

1. You need balls on the table.

1. You need walls at the side for the balls to
   bounce off.

1. You need pockets too.

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How to make an electron pool table

• Our electron pool table is really just a tiny
  transistor with some shape to it.

1. You need a flat table for the electrons to roll
   on (or in, as it turns out).

1. You need balls (i.e., electrons) on the table.

1. You need walls at the side for the electrons to
   bounce off.

1. You need pockets too (which as youll see serve
   many other important functions in our electron
   billiards).

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Some problems we need to deal with
We need to be able to stop this and get this
instead
If we want to be able to do this

• The electrons bounce off various things we dont
  want them to. These include

1. Impurities in the material.

1. Vibrating atoms in the material

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Incredibly tiny tables
10000? mag

• Our devices are much smaller than the width of a
  human hair. Actually, the contain nanometer
  (billionth of a meter) scale features and are
  part of nanotechnology.

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Nanotechnology
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Nanotechnology
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Coldest place in the universe

• Finally, the get rid of the vibrations, we need
  to make our samples really cold, less than a
  hundredth of a degree above absolute zero!

Hot! (-50C)
Cold (-270C or 3K)
Really cold (-273C or 0.01K)
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Electrons are waves not particles

• Electrons are strange creatures their wavelike
  properties mean that they can go around obstacles
  in a way that larger objects cant

• And they can then interfere with themselves just
  like in Youngs double slit experiment.

• If we apply a magnetic field, we can change this
  interference from constructive to destructive and
  back again, and this allows us to watch the
  electrons in the pool table!

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Electron pool tables
The little bumps are due to different possible
paths coming out of the exit hole. Were watching
thousands of electrons per second going through
our billiard here!
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But in all seriousness

• Our research is basically about finding out what
  happens at the outer limits of electronics,
  simply to see what happens.

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The Moral of the Story
But why, some say, the moon? Why choose this as
our goal? And they may well ask why climb the
highest mountain? Why, 35 years ago, fly the
Atlantic? Why does Rice play Texas? We choose to
go to the moon. We choose to go to the moon in
this decade and do the other things, not because
they are easy, but because they are hard, because
that goal will serve to organize and measure the
best of our energies and skills, because that
challenge is one that we are willing to accept,
one we are unwilling to postpone, and one which
we intend to win, and the others, too. John
F. Kennedy
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A change of topic
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So how did I end up in physics?
Video www.youtube.com
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So how did I end up in physics?

• My parents were too worried Id blow up the house
  or myself, so I wasnt allowed to have a
  chemistry set.

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Some of the perks of science

• The hours are flexible and the environment is
  good (even if you do have to work hard)

• You can get to play with expensive toys

• You can have a job you really enjoy with a lot
  of variety and challenges

• The travel is definitely a good part

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So how did I do it?

• First up, I did my HSC. Lots of science subjects,
  in my case phys, chem and maths. Oh, and english,
  no point doing science if you cant communicate!

• Went to university and did a Bachelor of Science
  degree majoring in Physics. I wanted to do
  experiments mostly, so I took as many lab
  subjects as I could.

• I stayed on to do an honours year as part of my
  B.Sc. and took two projects on semiconductor
  physics, to start specialising.

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So how did I do it?

• Next up, I started my Ph.D., which took 3 years.
  During my Ph.D. I spent four months working, on
  exchange, at the University of Cambridge in the
  U.K.

• International experience is important these days,
  so after that I took off to work in the U.S. for
  a couple of years, doing physics research at the
  University of Oregon.

• Came back a few years ago, now I spend roughly
  50 of my time teaching physics and the other 50
  of my time on research, mostly supervising
  research students.

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WHO should be doing physics research for a living?
Myth You need to be an Einstein to be
successful in Physics
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Playing pool with electrons
www.tallpoppies.net.au