Thread by @PnictogenHorses

I would like to talk about this business of *holes* in #semiconductor physics.

these _holes_ furnish us with a valuable lesson in how one can model the *absence* of something as though it were the *presence* of something else—as physical objects with discrete properties.

(1/x)

https://twitter.com/PnictogenHorses/status/1612545834285166592

an ideal crystal of silicon, or any other material used in making semiconductors, defines a fixed and predictable structure of nuclei in a rigid lattice. these nuclei might oscillate slightly about their mean positions within the lattice but mostly, their places are *set*.

(2/x)

the lattice of nuclei, in turn, defines an expected and predictable cloud of electron density that surrounds the positively charged nuclei. the overall charge balance through this structure is zero.

excess electrons, or *missing* electrons, produce deviations from zero.

(3/x)

when subjected to an electrical field, the free electrons are capable of moving through the rigid lattice.

electrons are *also* capable of temporarily occupying, and then leaving, the _holes_ in the lattice. the holes, in a sense, move around; they disappear and reappear.

(4/x)

but the hole is a vacancy, a gap; it's a place where an electron *would* be found, if the crystal lattice were perfect, but instead there's an empty spot.

does that mean the hole isn't "real"? a lot of #STEM nerds would probably say that. (@ID_AA_Carmack, any opinion?)

(5/x)

yet if you read the Wikipedia article on electron holes (en.wikipedia.org/wiki/Electron_…) you'll find that they're referred to as "quasiparticles": the holes can be physically modelled as though they were positive charge carriers moving through an otherwise neutral material.

(6/x)

I point out also that the hole is not just a *void*; if you could somehow examine the hole closely you'd observe that it contained electron density (simply _less_ than expected for a perfect crystal lattice) and other measurable physical properties. so, is the hole "real"?

(7/x)

I would argue that here—and in many similar cases—is where the distinction between "real" and "unreal", a distinction which Western culture and especially #STEM lord culture of the @JeffDean / @ID_AA_Carmack / @antoniogm sort, simply breaks down. "real" becomes arbitrary.

(8/x)

the person who defends the proposition that electron holes "aren't real" is now arguing against an entire body of physical theory that treats the holes as if they were real objects, real charge carriers. I doubt that's an argument that @JeffDean &c. are apt to win.

~Mona Drafter

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