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If we take the double slit experiment as a way of demonstrating the wave-particle duality, which types of particles would show an interference pattern?

For example, I know that electrons show such a pattern. But do protons, too? What about atoms? Where is the boundary between "wavey particles" and "classical particles"?

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The largest thing I have heard of is buckyballs: univie.ac.at/qfp/research/matterwave/c60 –  DJBunk Mar 11 '14 at 22:39
Wow, this is impressive! –  buschtoens Mar 12 '14 at 12:39

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up vote 4 down vote accepted

All of them. Even molecules show their wave-like nature, as does, in principle, every object. Speaking of these topics an interesting read about diffraction of C60 molecules is: http://www.univie.ac.at/qfp/research/matterwave/c60/

The point is that the wave-like nature of objects can only be observed at lengths comparable the object's De Broglie wavelength, defined by:

$$ \lambda = \frac{h}{p} $$

where $h$ is the Planck constant and $p$ is the object momentum. For an object moving at non-relativistic speeds you may remember that the momentum is defined as $\vec{p}=m\vec{v}$; the De Broglie wavelength is then inversely proportional to the object mass. The bigger an object is, the less relevant its wave-like nature is, and that's why in everyday experience we are not used to observing the wave-like nature of massive objects.

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I think the OP was mainly interested in the experimental side of things, so maybe you could expand a little on that? –  Danu Mar 11 '14 at 22:57
The theoretical explanation is already quite sufficent. Thank you! But yes, some experimental examples would also be very interesting. –  buschtoens Mar 12 '14 at 12:38
I'm not that expert on experiments... However there are "standard" double slit experiments, and in recent times people have tried to see wave-like behaviors for bigger particles... The furthest we got is the Zwillinger's experiments (C60 diffraction, the experiment I was quoting) as far as I know. –  zakk Mar 12 '14 at 18:39

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