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Ranku
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Holes have an effective mass. How is the mass of holes measured physically?
Ranku said:Holes have an effective mass. How is the mass of holes measured physically?
All I'm familiar with is the formula for effective mass: ħ2/2Ab2 (A is amplitude, b is atomic/lattice spaceing). I guess I'm trying to get a sense of if it might be possible to measure the effectve mass of a hole in a straightforward way, just as we are able to measure the free-space mass charge ratio of the electron from Thomson's apparatus.ZapperZ said:Go back a bit. Tell me if you know how the effective mass of electrons are measured.
Zz.
Ranku said:All I'm familiar with is the formula for effective mass: ħ2/2Ab2 (A is amplitude, b is atomic/lattice spaceing). I guess I'm trying to get a sense of if it might be possible to measure the effectve mass of a hole in a straightforward way, just as we are able to measure the free-space mass charge ratio of the electron from Thomson's apparatus.
I am also wondering if the mass of a hole has an explicit character like the mass of a free-space electron which can collide and scatter.
I am indeed aware of the distinction between effective mass of an electron in solid mass and the bare mass of an electron, which is why I mentioned 'free-space' electrons.ZapperZ said:There's a fundamental issue here that you are not understanding.
The "effective mass" of even electrons in a solid is DIFFERENT than the bare mass. This is because of the many-body interactions that are within the solid, and what allows us to define something known as a "quasiparticle". The "electron" that you measure in a solid is an "electron quasiparticle" (quasi-electron), not a bare electron.
Therefore, these quasi-electrons and effective mass do NOT exist in "free space"! So already requiring that we should be able to measure holes in such a situation is meaningless. Holes (or quasi-holes) can, by definition, only exist inside a solid and as part of the many-body interaction or renormalization.
The effective mass is "measured" from the band structure of the material. It corresponds to the second derivative of the band dispersion (the E vs k diagram). Depending on whether you are above or below the Fermi level, the curvature of the dispersion will give you the effective mass of quasi-electrons or quasi-holes. There is no difference between the two as far as the math is concerned.
This is why I asked you about your knowledge of what an effective mass is. I think this might be something you need to look at more closely.
Zz.
Ranku said:Suppose dark matter is the absence of matter, analogous to the hole being the absence of electron, and if the absence of matter means that the mass of dark matter cannot be directy detectable, can it still possesses a property like charge ?
But what if absence of matter doesn't have to be a vacuum - instead it is simply mass that is not material, say analogous to a purely spacetime object like a black hole, which too isn't material but possesses mass and probably charge (of course the analogy wouldn't extend to the origin of black holes)?Drakkith said:We can't suppose that dark matter is the absence of matter, as the absence of matter is simply a vacuum.
Ranku said:But what if absence of matter doesn't have to be a vacuum - instead it is simply mass that is not material, say analogous to a purely spacetime object like a black hole, which too isn't material but possesses mass and probably charge (of course the analogy wouldn't extend to the origin of black holes)?
I have a divide by zero issue with this concept.Ranku said:mass that is not material
Yes, you can measure the effective mass of holes (or electrons) directly. The easiest way is by cyclotron resonance.Ranku said:How is the mass of holes measured physically?
Could you direct me to some literature, especially online, that has more experimental details of what you described?Henryk said:Yes, you can measure the effective mass of holes (or electrons) directly. The easiest way is by cyclotron resonance.
You apply fixed magnetic field and measure absorption as a function of frequency. The cyclotron frequency is given by ##\omega = \frac {eB} {m_{eff}}##.
The field has to be strong enough so that ##\omega \tau >> 1 ##
Thank you for the pdf link; it's helpful.Henryk said:Oh boy, there is Google!
My first hit: http://physics.usask.ca/~alex/phys470/week1.pdf
The mass of holes refers to the measurement of the total mass of all the empty spaces or voids within a given object or substance. It is typically measured in a unit of mass, such as grams or kilograms.
The mass of holes can be measured using various techniques, including weighing the object before and after filling the holes with a known substance, or using specialized equipment such as a helium pycnometer or an optical microscope.
The mass of holes in an object can be affected by the size and shape of the holes, the material of the object, and environmental factors such as temperature and pressure. The method of measurement can also impact the accuracy of the mass of holes.
Measuring the mass of holes is important in various fields of science, including material science, chemistry, and engineering. It can provide valuable information about the internal structure and properties of a substance, and can help in understanding its behavior and performance.
No, the mass of holes cannot be negative. It is a physical quantity that represents the amount of matter present in the empty spaces of an object, and therefore cannot have a negative value. It can only be zero or a positive value.