Fermi Definition and 384 Threads

Homework Statement Hi I have the following integral over wavevectors inside the Fermi circle (we are in 2D) \int {dk_x \int {dk_y \sin ^2 \left( {k_x x} \right)} } Ok, so I know that kx2+ky2=kf2, so ky2=kf2-kx2 - this takes care of ky. But what about kx? What should this run from in order...

So, according to the Fermi function, the higher the temperature of a semiconductor, the higher the likelihood that the electrons can jump to the conduction band. But in superconductors, obviously the temperature is extremely low, so how does the Fermi level, band gap theory, and...

Homework Statement That's basically the whole question in the title there, ie; Derive an expression for the fermi energy of a 2d structure at 0 kelvin. 2. The attempt at a solution Basically the first part of the question had us sketching the Fermi-Dirac distribution function at 0K for...

Locally, Fermi normal coordinates are designed to correspond with direct measurement of distances (born rigidity). I also discovered that Synge's book on GR establishes that very locally, radar distance must match Fermi normal distance, but not in general (obviously). What I am wondering is...

Show that the kinectic energy of a three-dimensional fermi gas of N free electrons at absolute zero is (Mathematica code used) u = 3/5 N Subscript[\[Epsilon], F] Now I know total energy of N particles is this integral u = \!\( \*SubsuperscriptBox[\(\[Integral]\), \(0\)...

Sorry if someone already posted this link but did anyone see this in the news? http://www.nasa.gov/home/hqnews/2010/nov/HQ_10-295_FERMI.html What are people's opinions on what this might be?

For next year's Physics Open House the Department is planning to set up a bungee jump from the top of the physics building. Assume that one end of an elastic band will be firmly attached to the top of the building and the other to the waist of a courageous participant. The participant...

Aasslam u alaikum to all, i have confusion in knowing that " how fermi level form in a compound semiconductors e.g GaN, GaAs, etc. Thanks to all

Fermi Level Problem, help plssss ! Find the location of the fermi level with respect to intrinsic level if the probability that a state filled at the conduction band edge is equal to the probability that a state is empty at valence band edge. I am looking forward to your help.

Studying the free electron model I found the fermi dirac distribution and the book told me that when T->0 we have that the fermi energy is equal to the chemical potential... why?

I thought I'd present some plots for the Fermi-normal coordinates (only in the r-t plane) for someone falling into a black hole "from infinity". Fermi-normal coordinates radiate a set of space-like geodesics from some point on the worldine of an object - in this case, the worldline of an...

My syllabus doesn't include them in first physics course, and I am in engineering major. Should I try to practice them for myself or are they not very important?

In free electron 3D box model, we can calculate the density of state on the Fermi surface g(\epsilonf) easily, but how about the level spacing near the Fermi surface? I think this level spacing \DeltaE should satisfy \DeltaE=d/g(\epsilonf) where d is the degree of degenerate on the Fermi...

Homework Statement a) Calculate the Fermi energy for copper. b) Calculate the ratio of the number of occupied levels at an energy of 8.5 eV to the number occupied levels at the Fermi energy at room temperature. c) Based on your answer to a) and b) above, show that at room temperature...

Hi all, I've search for my question and found no answer. I think it should be pretty simple... Fermi energy corresponds to the last occupied energy, as I understand it. So, energy levels in the Fermi gas are all filled with two electron of opposite spins, up to the Fermi energy. Saying it...

Hi, I have come across a sentance in an article which I do not quite understand. H1 is just a perturbation Hamiltonian. Why will spin flips only occur at the Fermi level? Thank you

The almost simultaneous detection of low energy and high energy photons puts tight constraints on models predicting linear dependence of c on E. But it's very far from ruling out quadratic dependence. My question is, why do Lorentz-violating theories commonly predict linear rather than quadratic...

I'd really appreciate any insight on any of this since I've hit a wall. It is about the Fermi gas. --- My teacher did an example in class that didn't make much sense, and I'm trying to understand it. He had us take the real-part of the antiderivative of exp(ik(x-x'))dk, then evaluate it to...

Hi The dispersion of Bogolyubov quasiparticles in a d-wave superconductor is E(\mathbf k) = \pm \sqrt{\varepsilon (\mathbf k)^2+\Delta (\mathbf k)^2}, where ε(k) is the normal-state dispersion and ∆(k) is the gap dispersion. My question is: The Fermi surface (FS) of the normal...

Hi, Considering a pn-junction at thermal equilibrium, why does following count EFp=EFn-eVd=EF, where EFp and EFn are the quasi-Fermi energies in the neutral p- and n-type regions before equilibrium is established, with EFn>EFp, EF is the Fermi energy after equilibrium is established...

Hello, I have a question which has something to do with band structures etc: A two dimensional solid has two electrons per unit cell. The crystal potential is weak and the solid behaves like a free electron metal. Estimate the threshold for interband optical transitions in terms of the...

Homework Statement Problem 9.2(B) from Kittel Solid State Physics. A two-dimensional metal has one atom of valence one in a simple rectangular primitive cell of a1 = 2Å and a2 = 4Å. Calculate the radius of the free electron Fermi sphere and draw this sphere to scale on the drawing of the...

Hi Can somebody explain the meaning of the following sentence which is from Wikipedia: "Solids with a large density of states at the Fermi level become unstable at low temperatures and tend to form ground states where the condensation energy comes from opening a gap at the Fermi surface e.g...

Homework Statement What is the significance of Fermi Temperature? Homework Equations I know it is the ratio of the Fermi energy (or the chemical potential at the Fermi energy) to the Boltzmann constant. The Attempt at a Solution What does it MEAN? I've worked out the Fermi...

hi i was reading the following paragraph and i do not understand what it means. can someone explain what it means to me please? i know what the individual concepts are eg fermi line, hall coefficeint extended zone schemes, but am not grasping the concept of the two types of fermi surface...

Hello, Im just an amateur physicsist and was interested in Fermi Energy. Found a page http://http://hyperphysics.phy-astr.gsu.edu/hbase/solids/fermi2.html#c1" , that helped. However, I found the page and site a bit hard to understand in some places. Could someone please explain to me...

Hello, I have been lurking in the forum for a while. I have couple of questions that I cannot really find an answer to yet. If any of you have idea/suggestion/know of where to look at, I would greatly appreciate. First question: Let's put two different work function metal blocks to each...

I was reading this website, and I don't understand this last statement. http://hyperphysics.phy-astr.gsu.edu/hbase/solids/fermi.html It reads: "Since only a tiny fraction of the electrons in a metal are within the thermal energy kT of the Fermi energy, they are "frozen out" of the heat...

Hi Strictly from the definition of the Fermi level as the highest energy occupied at zero temperature, it seems that in the presence of a band gap the Fermi level (Ef) could be placed fairly arbitrarily anywhere between the conduction (Ec) and valence (Ev) bands, since the density of states is...

Hi. Does anyone know how to calculate the fermi level for the conduction band in a quantum well?

I've tried to look this up online, but I can't find it anywhere. I'm just looking for the intrinsic fermi energy of silicon E_i ? Can someone maybe direct me towards a website where I could look it up? Either that, or is there a way to calculate it from the energy gap for intrinsic silicon...

Can anyone help explain how one can apply information say from an energy band diagram of an element/compound to its respective fermi surface / "sphere"? I understand there is a direct relationship, however, I can seem to physical interpret how one is able to say look at the energy band...

Why is it called degenerate ?? Is it because all levels upto fermi level are filled or all degeneracies of the energy levels that are present occupied at T = 0k . In deriving the average occupation no. for a deg fermi gas , we have used classical idea of momentum that is integrating over a...

Why is it called degenerate ?? Is it because all levels upto fermi level are filled or all degeneracies of the energy levels that are present occupied at T = 0k . In deriving the average occupation no. for a deg fermi gas , we have used classical idea of momentum that is integrating over...

Effect of Doping on Fermi Energy... I was wondering if anyone could give me a clear answer on why doping a semi conductor raises or lowers the fermi energy depending on n or p type semi conductors. There seem to be a few standard ways of explaining this, some to do with charge conservation or...

A question for those of you who know about the distribution of dark matter in the galaxy: Do we know how "clumpy" dark matter is? Can we tell yet whether dark matter is distributed about as densly as a gas or whether it's possible that there are the equivalent mass distributions that might...

I have a question that is puzzling me as always...The Fermi-Dirac distribution function is (at T=0): f\epsilon=\frac{1}{e^{\beta(\epsilon-\epsilon_{F})}+1} and we know that we can subsitute f\epsilon by 1 for \epsilon< \epsilon_{F} and 0 otherwise. However what is f(-\epsilon)? The answer is...

Guys, I have two questions: (1) what does a vanishing Fermi energy mean? (2) I have also calculated the phonon self energy for the electron phonon interaction in graphene. However in one of the papers, they state that one needs to subtract from this self energy the case of vanishing Fermi...

Hello, Im working on a paper on solar cells and i came across the term "Fermi level". What exactly is the Fermi level in this context: "The working voltage produced by the device is the difference between the chemical potential of the titanium dioxide (Fermi level) and the redox...

I know that when a metal is compressed its fermi energy is increased. I would attempt to explain this by saying, "as the volume has been decreased, so has the allowed number of particle in a 3D box states, thus as we have the same number of electrons and fewer allowed states, and the pauli...

As I know chemical potential of two reacting substances strongly depends on difference in Fermi energy between them. Fermi energy is inversely proportional to the mass of particles. Does that mean that Fermi energy of bare proton will be 2000 time smaller than that of electron? Usually...

How can an electron's momentum be less than the Fermi momentum? Since the Fermi momentum (energy) is measured at absolute zero.

Fermi Energy, Quantum mechanics Electron levels and degeneracies thereof in a system are: W1 = 0 eV, 10^23 /cm3 Valence band W2 = 0.9 eV, 5x10^20 /cm3 Donor level W3 = 1 eV, 2x10^23 /cm3 Conduction level Total number, n, of electrons in the system is (10^23 + 5 x 10^23)...

Homework Statement I have to find the Fermi Coupling Constant using my measurement of the muon lifetime. My measurement is 2.1786x10^-6s Homework Equations G_F=\sqrt{\frac{192.pi^{3}}{\tau.m_{\mu}}} The Attempt at a Solution I tried plugging in the numbers that I have and I get...

Hi everyone! I wanted to ask if in your opinion is it right to say that band structure calculations (and hartree fock calculations) could live in a framework of the fermi liquid theory where quasiparticles are one-electron states (which could be or not could be the case)...

can any1 explain what fermi level is simple explanation also how are minority charge carriers formed and i can't understand the energy band diagram of pn junction that how both the fermi levels become equal WHAT IS MEANT BY THAT FERMI LEVEL i read in hyperphysics but i can't understand it...

Relations for an ideal Fermi gas: \frac{P}{k_BT}=\frac{1}{\lambda_D^3}f_{5/2}(\lambda) \frac{1}{\upsilon}=\frac{1}{\lambda_D^3}f_{3/2}(\lambda) But in some book books I find \frac{P}{k_BT}=\frac{g}{\lambda_D^3}f_{5/2}(\lambda)...

Homework Statement Hi all I can't seem to figure out, why semicodunctors do not have Fermi surfaces. At T=0K, there are no electrons in the conduction band, and thus there is no Fermi surface - all OK here. But at T > 0K, there are electrons in the conduction band. Why is it then that it...

Hi there, i've already read some topics in this forum about the fermi-energy/chemical potential. I've also read the article "The chemical potential of an ideal intrinsic semiconductor" from Mark R. A. Shegelski which made the whole thing a little bit more clear to me. but there are some...

In the theory of superconductivity BCS theory is given eigen - problem -\frac{\hbar^2}{2m}(\Delta_{\vec{r}_1}+\Delta_{\vec{r}_2})\psi(\vec{r}_1-\vec{r}_1)=(E+2\frac{\hbar^2k^2_F}{2m})\psi(\vec{r}_1-\vec{r}_1) Why E+2\frac{\hbar^2k^2_F}{2m}? Maybe because is Fermi sphere is centered in...