Fermi Definition and 384 Threads

1. There are many different definitions of the location of the top of the atmosphere – the near edge of outer space. • Until around 1600, it was believed that the Earth’s atmosphere extended throughout space (recall that the Earth was also considered to be the center of the Universe until...

Hello guys, very short question :), why does Fermi level go down with temperature? is there some physical explanation or discussion for this? apart from mathematics (well, some mathematics would be cool if necessary :)) Find attached some cool curve about this ;) Thanks guys :)

please help in this problem what are these basis and what are there there properties.how i can i put there values to solve my problems. ˆB  = ( 1 2  + +)er er  + ( 1 2  − +)e e  + (× + !)er e  + (× − !)e er  . (4.13) where eµ  are co-frame basis satisfying...

Hi People. I was looking at the derivation(s) of Fermi-Dirac Statistics by means of the "most probable distribution" (I know the correct way is to use ensembles, but my point is related to this derivation) and it usually employs Lagrange multipliers and Stirling's approximation on the...

I'm reading Enrico Fermi's "Thermodynamics" book. In page 3 of his book, he says: It is evident from what we have said that the knowledge of the thermodynamical state alone is by no means sufficient for the determination of the dynamical state. What does he mean by dynamical state...

at Fermi lab they create anti-matter or I guess they don’t create it but they synthesize it , where do they keep it so it doesn't react with regular matter and produce light.

Homework Statement We must calculate the Fermi energy of metallic potassium at 0K. We have aleady found the number of atoms per m cubed, we are told that each atom contributes one electron to the free electron gas. Homework Equations Fermi energy = ((hbar^2)/2m)(((3Pi^2)N)/V)^3/2 The...

Homework Statement Show that the fraction of electrons within kT of the fermi level is equal to 3kT/2Ef, if D(E) = E^1/2. Homework Equations f(E) = 1 / ( exp(E-Ef)/kT + 1 ) fermi distribution N = integral from 0 to inf of D(E)f(E)dE = total no. of electrons The Attempt at a...

Hello, In few days, I have an examination, and I still have some dark zone in my head! If somebody could help me by giving me some advices/answers/way of reflexion/books to consult, it could be very great! Here is my questions: How to determine energy levels and wavefunction of the...

At 0k, why is fermi level halfway in bandgap?? Fermi Level is defined as the maximum energy an electron posesses at 0k, which appears to be midway in the bandgap. I learned that in the bandgap, there are no available states (i.e. no wavefunctions of electrons) hence, no electrons can possibly...

When we are calculating the fermi energy, we say that each energy level is 2 fold degenerate and the fermions stack up into higher and higher energy level due to the Pauli Exclusion Principle. My question is: The Pauli Exclusion principle only says that we can't put different fermions into the...

Homework Statement I am wondering about something: Calculate the Fermi energy for the neutrons confined to a nucleus with 40 protons and 50 neutrons which roughly forms a sphere of radius 4.6 10^(-15) m. Homework Equations the formula of the fermi Energy is EF=...

I am wondering about something: Calculate the Fermi energy for the neutrons confined to a nucleus with 40 protons and 50 neutrons which roughly forms a sphere of radius 4.6 10^(-15) m. the formula of the fermi Energy is EF= ((h-bar)^2*(3*pi^2*n)^(2/3))/2m m:mass of electron, n = number...

relation of fermi energy in 3D is E=h(cut square)k(square)/2m, if i want a relation of fermi energy in 2D,what should i do?

Hi everyone I need the historical articles that bose and fermi integrals were defined for the first time. Can anyone help me?

Homework Statement Consider 2 fermionic gases, each made of 10^6 atoms occupying 10^-3 m^3 volume: tritium, the nucleus containing one proton and two neutrons, and potassium, 19 protons and 21 neutrons. Which gas do you have to cool more in order for a Fermi surface to form? Find the ratio...

For a = 5Angstrom and n = 3 calculate kf and compare its magnitude with the dimension of the Brillouin zone, (all in 2D, square lattice). Relevant eqn: kf = (2*pi*n)^1/2 Here is my solution: kf = (2*pi* (3/a^2))^1/2 = ((6*pi)^1/2)/a =8.7x10^9 m^-1 1st BZ = (2*pi/a)*1/2...

Hi, Is this right: Fermi velocity is the velocity of electron-wave in a conductor. Why is it called Fermi velocity, i.e. what is its relation with Fermi energy, etc.. Thanks a lot. Cheers

Hi all, I'm studying on the current transfer at quantum level and I have a point that is not so much clear. While reading the Fermi sphere from the book "Current at the nanoscale", I could not understand the expression: The number of electrons in the conductor, N, is the ratio of the...

Homework Statement What fraction of the 3s-electrons of sodium is found within an energy k_b*T below the Fermi level? (Take room temperature at T= 300k) Fermi level for Na is 3.2 eV Homework Equations F(E) = 1 / {exp((E-E_f)/k_b*T) + 1} The Attempt at a Solution From what I can...

http://www.symmetrymagazine.org/breaking/2009/02/19/most-extreme-gamma-ray-blast-also-probes-quantum-gravity/Fermi%20Observations%20of%20High-Energy%20Gamma-Ray%20Emission%20from%20GRB http://www.nasa.gov/mission_pages/GLAST/news/high_grb.html...

Hi, Ok, so let's say we have a non-degenerate n-type semiconductor such that the Fermi-level/chemical potential is somewhere in the bandgap (probably needs to be low temperature). Typically in a metal you would say that the Fermi velocity is \hbar k_F/m_e. But since the Fermi-energy is below...

Homework Statement (I copy-pasted the question) Consider N non interacting electrons inside a 3D box similar to the one we saw in class, but this time it is not cubical, i.e. Lx = Ly \neq Lz. 1. Calculate the fermi energy as a function of N;Lx;Lz;me... 2. What happens if we take Lz --> 0...

if fermi level is defined for 0K, then how does it vary in a semiconductor with temperature. also, why will the formation of holes affect the position of fermi level(by introducing acceptors). have i misunderstood something? please clear my doubt.

Hi, Im just wondering, why the fermi level rise up with raisng up the temperature when donors are present in Extrinsic semiconductor? thanx

I've been reading an article that refers to the distance of a fermi. What is this in SI units? A google search isn't proving fruitful. Cheers!

I've found the simplest hopping Hamiltonian for fermions (diagonal in momentum space) has a so-called Fermi sea ground state. H = -2 t \sum_k \cos(k) f^+_k f_k (t is some parameter in units of energy). How do I evaluate the expected value of the spin exchange operator S_x \cdot...

Hi everybody, I have the following homework assignment: 1. Derive the expression of density of state D(E) in free electron system. D(E) = \frac{m\sqrt{2m}}{{\hbar}^3\pi^2}V\sqrt{E}, (1) where m and V are electron mass and volume of the system, respectively. 2...

hello to everyone. It is normally said that in semiconductors the Fermi level is half way between the valence and the conduction band. I have the following question on that: what does it mean that the Fermi level is in the band gap? It should mean that the maximum energy of an electron in the...

i know this is a simple question, but i have been looking for a while (maybe 15 min) and i cannot find what is so special about Cu, Ag, and Au? i know there is something special about these 3 metals. something that none of the other metals have. i remember it having to do with fermi velocity /...

In classical statistical mechanics, temperature of a system is the measure of its average kinetic energy. In quantum statistical mechanics, Fermi energy corresponds to last filled level at absolute zero and corresponding temperature is the Fermi temperature. Is the Fermi temperature also take...

[SOLVED] Fermi Dirac- missing something from Ashcroft derivation Homework Statement Deriving Fermi Dirac function following ashcroft all good up to equation 2.43 but then it does the folowing at 2.44 and I can't see how you reach 2.44. Homework Equations as (2.43) f_{i}^{N}= 1-...

Homework Statement (a)If a silicon crystal is doped with 10^15 cm−3 phosphorus atoms, find out the electron concentrations and hole concentrations in the silicon at room temperature. Find out the Fermi level. (b)Repeat at temperature = 0K Homework Equations n*p=ni^2...

[SOLVED] radius of the fermi sphere Homework Statement On page 249 of ISSP, Kittel says that the radius of a free electron Fermi sphere is k_F = \left(3 \pi^2 n \right)^{1/3} where n is the concentration of electrons. I don't know why that is true. EDIT: never mind; they derive that on...

Can someone please help with this problem. I've been looking at it for a week! I can't figure out what equation to use. A si sample with 10^15/cm^3 donors is uniformly optically excited at room temperature such that 10^19 EHPs (Electron Hole Pairs) are generated per second. Find the...

Can someone please help with this problem. I've been looking at it for a week! I can figure out what equation to use. A si sample with 10^15/cm^3 donors is uniformly optically excited at room temperature such that 10^19 EHPs (Electron Hole Pairs) are generated per second. Find the...

in a Fermi gas, we know that when the temperature is much less than the Fermi energy, it becomes a degenerate gas. does this mean the chemical potential of the system be very large?

I am reading 'Mesoscopic electronics in Solid State Nanostructures', second edition, by Thomas Heinzel. And I find it a bit too difficult from time to time. Especielly on the concept of Fermi level pinning in doped semiconductors. Does anyone know where to find a good explanation for this...

fermi level?? is there any relation ( equation) that give the fermi energy level in terms of Na and Nd the concentration of dopant??

My thoughts "Emergent physics: Fermi point scenario G.E. Volovik" http://arxiv.org/abs/0801.0724 Emergent physics: Fermi point scenario G.E. Volovik What if Volovik is correct that the true TOE is some sort of Fermi point scenario? 1 string theory is dead, and SM particles are not...

I feel dumb that I can't figure this out. I'm sure its something simple that I'm just not seeing, but its really frustrating. Homework Statement How many electrons (in percent of the total number of electrons per mole) lie KbT (ev) below the Fermi energy? Take Ef=5eV and T=300K...

I understand that for a semiconductor p-n junction under zero voltage, the Fermi level is constant throughout the junction because that is the condition for a system in thermodynamic equilibrium. I also understand that p-n junction under applied voltage (forward or reverse) is not a system in...

I don't really understand why the Fermi-Function is often used to describe superconductors. According to the BCS theory Cooper pairs should be Bosons with Spin 0. Wouldn't it make more sense to use the Bose-Einstein-Function? Thanks Tanja

Relating to Fermi Paradox, how far away from Earth might the oxygen signature of our atmosphere be spectographically detectable? The flip side is how far away might an exo-terrestrial planet's atmospheric oxygen signature be detectable? For example,Gliese 581 c,d are larger (5-7x earth)...

Suppose we have particles of kind B, that consist of two fermions of kind F. Now the particles B satisfy the Bose statistics. But what precisely does this mean? If we have four F particles, the system is described by a wave function \psi(x_1,x_2,x_3,x_4) Suppose the particles 1 and 2...

Hello all! My professor talked about the quasi fermi levels in my Photonics class. While he did make a good effort, I still am not able to understand the concept. I do plan on going to him on Tuesday to get a clearer idea. But I was wondering if any of you folks could give a general...

Homework Statement The probability of a person quantum mechanically tunnelling through a wall Homework Equations The Attempt at a Solution I'm not too sure how to approach this problem, I calculated the de Broglie wavelength of the person (mass = 60kg, velocity = 30 m/s; These values are...

In what kind of experiments does the fermi statistics show? What kind of experiments have been carried out to verify that electrons obey fermi statistics? This fermi statistics stuff has been quite theoretical only in texts I have encountered so far.

Ahoy, I'm trying to do a calculation of the electron-electron self energy of a Fermi Liquid, which is supposed to exhibit a dependence on the square of the temperature of the system. I've read through the first six chapters of "Green's Functions for Solid State Physicists" by Doniach and...

Hi I am new to solid state. I just read about fermi gas in a cube. For some reason the author used periodic boundary conditions? Why didn't they choose finite well potential where the height of the well is related to the work function?