Recent content by nmbr28albert

After some digging, I found that it actually isn't true that the valence band maxima is always at k = 0. In lead sulfide for example, the valence band maximum is at the L point.

In general, materials are either direct or indirect materials. For direct materials, both the valence band maxima and the conduction band minima are at k = 0. For indirect materials, only the valence band maxima is at k = 0 and the conduction band minima is at some other non-zero value of k. In...

One of the most important reasons for E-k diagrams (or more commonly known as bandstructures) is because of interactions of a material with photons, phonons, etc. In all interactions, energy and momentum must be conserved. By using E-k diagrams, one can keep track of both energy and momentum at...

In a crystal, the index of refraction is always calculated in the Lorentz oscillator model by examining the electronic response to an incident field and assuming a stationary nucleus. Is there however, any contribution to the index from the ionic nuclei in the background? I assume since I've...

When calculating the dielectric constant of metals using the Drude model, in the low frequency regime (infrared and beyond) one gets an approximately pure imaginary value: $$\epsilon(\omega) \approx i\frac{4\pi n e^2\tau}{m_e\omega}$$ which gives an absorption coefficient: $$\alpha(\omega)...

From personal experience, I would recommend that you avoid "modern physics" textbooks altogether. By trying to dumb things down to a lower level than necessary, a lot of important details get omitted or stated in weird ways. Avoid Tipler, and just read the first few chapters of Griffiths for the...

Physics graduate student at the University of Michigan here. I happened to do my undergrad here as well, and I took a quick look at the free response questions. First of all, if you go to any decent size university the intro physics classes are all humongous. This means no free response, and...

In band theory, one of the first things that is always stated is that a completely filled band, such as the valence band at low temperatures, will not contribute any current because the average velocity will equal zero. This is usually justified by showing a plot of a parabolic bandstructure...

One result of the Drude model of metals is that metals cannot sustain an electromagnetic wave for frequencies lower than the plasma frequency - since the wavevector is imaginary the wave will be evanescent and won't propagate. The books I've read say however, that this means the metal will...

One way to solve the simple LC circuit with 1 inductor and 1 capacitor is to use the Lagrangian formulation of mechanics and consider charge q as the generalized coordinate. When writing down your Lagrangian, the energy of the inductor \frac{1}{2}L(\frac{dq}{dt})^2 is treated as the kinetic...

In the Stern-Gerlach experiment, we have an inhomogeneous magnetic field aligned with the axis labeled z. The two distinct deflections are caused by the force from two distinct magnetic moments \mu = \gamma S. I understand that the spin larmor precesses around the field and that the expectation...

I see, so since the spin operators cannot be derived from the position and momentum operators, it seems to me that the original Schrödinger equation is not the complete non-relativistic limit of the dirac equation, which is actually the pauli equation. In the historical context then, was the...

Hello everyone, this has been on my mind for a while and I finally realized I could just ask on here for some input :) I think in general, when most people start learning quantum mechanics, they are under the impression that the wave function \Psi represents everything you could possibly know...