Considered a simple system composed by 2 electrons, like the H2 molecule, the exchange interaction is isotropic: there's no preferential direction of the spins in physical space. What is the reason? Maybe the fact that the exchange interaction deals with only with the Pauli exclusion prinicple...
fs is the step in the frequency axis: 5*10^{-11} is the total temporal window (50 ps), n is the number of the time axis. SO fs is the inverse of the time step.
f is the frequency axis, but for the plot I use f0 because it is zero-centered and it shows the two parts (positive and negative) of...
I have just try to set m=n and the problem has not been solved. Maybe the problem could be in the definition of the frequency axis f0 or, I think most likely, in the edge effects of the FFT: the two peaks that I see are at the edges of the frequency axis.
it can be n>m. In that case MATLAB adds zero values to the signal's vector, in order to make the length of the vectors match. At least that's what I have understood from the Mathlab help..
I have tried your code: it works. Now I have added the following part, which should provide the Fourier transform od the oscillations. The problem is that I can see two sharp peaks at 10^14 Hz for x(1) oscillations and 10^12 Hz for nuclei: they are shifted by one rder of magnitude in comparison...
Thank you for your help MasterX! What y suggested works, but I need a single expression for both the oscillators. In this way I can add the coupling terms. I found out that the main problem was the solver: the ode45 is not suitable for stiff problems, like the one I am considering.
Thanks again!
At my department liquid nitrogen free. The point is that if you want to use it, you need the transfer line and the cryostat: these are really expensive! A cryostat's price lies in the range between 10000-40000 € more or less.
I think that a research project about superconductivity is not feasible with a 500$ budget. It is due to the fact that achieving the superconducting state requires liquid helium or liquid nitrogen (if you work with cuprates). These two materials are both expensive: so I think there's no chance...
Strictly speaking the fermi level can be defined only in metals, because of the condition of half-filled bands. However usually it is said that the fermi level in the semiconductors lies at the half of the band gap; this fact is reported in every introductory solid state test. Maybe in one of...
I am a Matlab rookie. I need to solve numerically the following second order differential equations
d^2x/dt^2 + w0_(el) * x = e/m_e * E - K3/m_e * x *y;
d^2y/dt^2 + w0_(v) * y = - K_3/2M * x^2;
I have started to deal with only the harmonic part of the problem. So I tried to solve...
"The thermodynamic variables are consistent throughout" doesn't mean that they always have the same value. I mean, consider a cup of water: you can change its volume, pressure and temperature (within certain range of values) without changing the phase (no boiling or freezing), so you can change...
Hi! I suggest you to read the book "Introduction to statistichal mechanics" Bowley, Sanchez; there are a couple of chapters regarding different phases balance and phase transitions.
I try to answer your questions:
1 I guess so, but I don't know wheter exist some exotic systems that can...
I've recently find out that is possible to describe tunneling effect by means of the instantons.
Of course there are other methods to compute the transmission probability (WKB for example), but the real utility of this technique is that it can be applied in Quantum Field Theory (and also in...
If you want to describe the interaction between a photon and an electron, you have to consider the potential that describe the interaction. I mean, if you are looking at the consequences of the interaction on the electron, you have to put the potential in the Schroedinger equation, then you have...