Pardon me but this explanation is saying amplitude modulation causes side bands or varying transmission causes sidebands while the question is how the sideband arises. It's akin to stating that sum frequency generation in a crystal produces new frequencies without exploring the specific...
Ok great. So what is the physical process that generates these sidebands?
My main problem is that I fail to reconcile the spectra broadening effect due to modulation with any physical process that I know.
Upon reconsideration, I acknowledge my oversight in assuming linearity in modulation, especially given examples like AM that illustrate its nonlinear nature. This prompts me to question whether modulation using an optical chopper is also categorized as a nonlinear process. If it is indeed...
Hi, I believe my primary concern is the linear case. I am concern with the modulation of light signal which can be achieved through a linear process (I believe). In that case the time signal is changed so does that mean the new frequency calculated using FT is a mathematical artifact?
Thank you all for the insights shared. It appears that indeed new frequencies are generated through modulation, but the precise mechanism remains elusive. Some responses mention mixers, yet explanations about the actual generation mechanism are sparse. Basically all explanation just says that...
Suppose I have a pure sine wave. Upon Fourier transforming (FT) the time signal, I obtain a delta function in the frequency domain. If I subsequently modulate this sine wave with another function, for instance, a Gaussian, the delta function in the frequency domain will broaden. I'm curious...
I am trying to understand how do we see the spin accumulation due to Rashba-Edelstein effect. I mean everywhere I look people just say a shift in the bands due to e-field which results in spin accumulation in the transverse direction (y in this case) as shown
Can somebody explain how to see...
I found a video by prof. C. Kane and he said 'Berry phase arise whenever you have a Hamiltonian that depends continuously on some set of parameters'. So that means we can have Berry phase without any perturbation since the Hamiltonian depends on k.
I still don't see how Berry phase can arise...
We take the unperturbed Hamiltonian and calculate E(k) then look at the position of E_F? or can look at the number of electron(s) per primitive unit cell I guess?
Yes and this is exactly my question. To calculate Berry phase means the Hamiltonian has to change but when characterizing a material using topology, why does the Hamiltonian changes? Can't I calculate the topological invariant without applying any field? If I can, then the Hamiltonian doesn't...
Thank you for your reply. I see that the paper you cited and your explanation revolves around a changing Hamiltonian. Does this mean that this close loop evolution is only present when we have some perturbation that continuously change the k? When we talk about topological materials, I thought...
I am trying to understand how is topology used to characterize materials. So I understand that to calculate the Berry phase you will parameterize your Hamiltonian and change this parameter in some way and return to the initial value. What I do not understand is what does this changing of...