Fermi Definition and 384 Threads

I am new to solid state physics, having been in computational chemistry (quantum mechanics) for the larger part of my career. Hence have a lot of newbie like questions that are not easily answered by google/wikipedia searching. 1)In viewing a 1-dimensional band gap diagram, crossing the...

why cdw occurs at low dimensional solids with anisotropic fermi surfaces that have prominent nesting vectors?/ what it means : cdws are also common at the surface of solids??where they are more commonly called surface reconstruction or dimerization . PLZ tell me about two dimensional Fermi...

Hi guys. I am currently studying Sub-atomic physics and it seems to me that there are different formulas that work in different frame of reference. In particular, I would like to ask: 1. Which frame should we use in applying Fermi's Golden Rule? (I've read somewhere that the matrix element...

Estimate the Fermi level position EFn for a Si sample at room temperature that is doped with 1015 shallow donors cm-3. From coursework I've gatherred over the year I understand the equation needed is: EF=EC-kT ln(NC/n) n, being equal to the donor concentration EC is the conduction...

Homework Statement Consider an electron gas of density n_{0} in three dimensions that is completely ferromagnetic: all electron spins point in the same direction. Derive: a) The Fermi wave vector in terms of n_{0}. b) The parameter r as the radius in atomic unites that encloses one unit of...

Homework Statement Calculate the Fermi energy for magnesium, assuming two free electrons per atom. Homework Equations {E_F} = \frac{{{\hbar ^2}}}{{2m}}{(3{\pi ^2}\rho )^{2/3}}, where \rho = q\frac{N}{V} and q is the number of free electrons. The Attempt at a Solution q = 2, so...

For any system where the thermodynamic limit exists, we know that the internal energy U, the entropy σ, the total particle number N and the total volume V are all extensive. Because of this, we know that the Euler relation holds true U = -PV + \tauσ + \muN and that the chemical potential...

Hi I am attempting to calculate the mass of the W boson according to one loop energies using the equation, Mw2=(πα/GF√2)/sin2θw(1-Δr) where (Δr)top=(3GFMt2)/8√2π2tan2θw using values:- α=α(MZ)=(127.916)-1 GF=1.16634×10-5 sin2θw=0.23116 =>...

I'm trying to learn about Luttinger's sum rule, but I haven't taken QM yet, and the papers on the topic are very difficult to understand without it. However it seems qualitatively like the Luttinger surface is equivalent to the Fermi surface. If this is not the case, what's the difference? Does...

Hi, I was wondering if anyone could clarify for me what the correct regime is for treating the electrons in a material as a Fermi gas. When is it that you must use Fermi liquid theory?

Homework Statement Sodium is, to a good approximation, a monovalent free-electron metal which has the body-centred cubic structure. (a) Calculate the ratio of the Fermi wavevector to the radius of the largest sphere that can be inscribed in the first Brillouin zone. Remember that the...

Homework Statement The atom He^3 has spin 1/2 and is a fermion. The density of liquid He^3 is 0.081g/cm^3 near absolute zero. Calculate the Fermi energy \epsilon_F and the Fermi temperature T_F Homework Equations \epsilon_F = \frac{\hbar^2}{2m}(\frac{3 \pi^2 N}{V})^{2/3} T_F =...

Homework Statement At T=0, what is the largest density that a gas can be completely spin polarized by a magnetic induction of 10 telsas Homework Equations μn= 10^-26 J/T mass= 5*10^-27 kg spin= 1/2 The Attempt at a Solution I am really not sure where to begin. The spin...

Hi, I would like to get suggestions about the physical meaning of the (1) flat-band voltage and the (2) Fermi-level. Before being marked as newbie, I'd like to point out that I know how to calculate them and know that the (1) flat band voltage is the one which you apply, the energy band...

What are the "natural" generalizations (if any) to Bose and Fermi statistics? fermions: 1 particle per state Bosons: unlimited number of particles per state do people consider things in between like states with a capacity n? are there other generalizations of these statistics? Thanks!

Hello. I was womdering does anyone know any good resources of information on Fermi level de-pinning & Schottky barriers? I have been hunting around online, with not much luck. I thought someone here might be able to suggest some things. Thanks. Seán

Homework Statement Consider an electron gas with a density of states given by D(e) = ae2. Here a is a constant. The Fermi energy is eF. a) We first consider the system at zero temperature. Compute the total number of electrons N and the groundstate energy E. Show that the average energy per...

My understanding is that the Fermi temperature is a measure of the energy of a system at its lowest energy state. This suggests that at the Fermi temperature is a minimum temperature where the system can't radiate away any more energy. If this were a physical temperature it seems the system...

Hi I've been searching on the web for this two topics, band structure and fermi surface, both of copper. I can't find any of them from a free source, I am doing just a report of my class of introduction to solid state and I just have found this two things in articles that must be bought. If...

Homework Statement Here's what the question says. "Consider a cube of gold 1 mm on an edge. calculate the approximate number of conduction electrons in this cube whose energies lie in the range from 4.000 to 4.025 at 300k. Assume Ef(300K) = Ef(0)." Homework Equations Well, I know...

Fermi Level -- clarification needed Homework Statement Revered Members, Can i know what is meant by fermi level? I googled this, but i could not understand. One site says Fermi level as top of collection of electron energy levels at absolute zero. Homework Equations The Attempt...

Homework Statement Calculate the electron concentrations (# electrons/atom) needed for the fermi sphere to contact the zone faces (first bril. zone edges) in BCC and FCC structures. Homework Equations kf = (3*pi^2*n)^(1/3) where n is # electrons per atom. For cubic structures...

Hi all, In the solid state physics course I took a year ago we used the chemical potential μ which appeared inside the fermi-dirac distribution function to describe the energy that above it no electrons resides and below it they all reside as the temperature reaches 0 kelvin. Now, when I...

When Fermi was asked if he believed in the existence of E.T.s he replied "where are they?" and I think the idea was that if there were E.T.s they should have colonized the galaxy by now. What I am curious about is ... given the fact that the ability to detect earth-like worlds with signatures of...

Homework Statement Calculate Efi with respect to the center of the bandgap in silicon for t= 200, 400, 600 kelvin. Homework Equations ni = Nc e^-((Ec- Ef)/(kt)) k = boltzman constant t= temperature in kelvin Ec = energy level of the conduction band ef= fermi energy level ni=...

Hello. I am doing an electronics degree, and we were told in our solid state devices class that "work function is the energy required to release an electron from the influence of the material to vacuum. When the system is brought together to form the MOS capacitor, the Fermi levels must...

Hey everyone, So unfortunately I haven't taken Stat Mech yet (and my GRE is in a week), but through casual reading and forums I've gathered what the concept of fermi temperature and energy is...or thought I did. From what I understand, below the fermi energy (the fermi energy within an atom...

1. Fermi level is also defined as highest energy level at which electron can exist at 0K then it should be top of valence band but why is it in between conduction band and valence band ( in forbidden gap)? It should be in conduction band or valence band. How to explain this? 2. If density of...

Fermi level in an extrinsic semiconductor(after attaining thermal equilibrium) is said to be invariant (constant ) , and the proof uses the fact 'no current must flow thorough any cross-section'..But I don't think its true, charge will be transported due to diffusion and this is countered by...

Is it weird that at absolute zero in a metal, electrons at the fermi level still move around at the fermi velocity. Is the notion that everything stops at absolute zero incorrect? Thank you

how is the relationship between fermi level and band structure of solids can effect electrical conduction properties of a material?

A way to write Fermi golden rule is W_{fi} = \sum{\frac{d P_{fi}}{dt}} = \frac{2 \pi}{\hbar} \sum_{f} |V_{fi}|^2 \delta(\varepsilon_f - \varepsilon_i) where "i" is the initial unperturbed state and "f" is the final state of an ensemble of final states (i sum over them). But because of...

I'm trying to figure out the sensitivity of the Fermi LAT, in units of spectral flux---e.g. Jansky, or a limiting magnitude which could easily be converted. I've only found sensitivity in traditional high-energy terms, e.g: 4\times10^{-6} \textrm{ photons/s/cm}^2 for photons above 100 MeV, with...

Homework Statement This question is about the Fermi nuclear model (see Das & Ferbel page 56 or http://www.e12.physik.tu-muenchen.de/stud/vorlesungen/fabbietti/WS2007/Lecture3.pdf" ). Let the nucleon mass be m, the number of nucleons be A and the number of protons be Z. Assume a hypothetical...

Am I right in thinking Fermi type beta decay is helicity suppressed, due to the necessity of having a right handed electron? This was implied but not explicitly stated in my lectures. And is this why Gamow-Teller type beta decay is the generally favoured mode?

I'm having a bit of trouble understanding what's going on with the energy diagram of a PN junction. For your normal undoped semiconductor at zero bias, if you're plotting the energy as a function of distance along the material then you've just got the two horizontal lines where the upper one...

Homework Statement Imagine non-interacting electrons confined to a two-dimensional plane between atomic layers within a crystal. Discuss the properties of the resulting fermi electron gas. Homework Equations None The Attempt at a Solution I don't really have any idea how to go...

Hello. There is no agreement on the meaning of terms electrochemical potential and chemical potential (see for example http://web.mit.edu/6.730/www/ST04/Lectures/Lecture26.pdf"). While proper definitions would call chemical potential to \mu\equiv\left(\frac{\partial U}{\partial...

I have taken several courses in semiconductors at the undergraduate level. Both the pure physics part (k vectors) and the more engineering parts (silicon processing, band diagrams) etc. So for all the junctions (Schottky, Ohmic, p-n) - I have never managed to imagine the idea of the Fermi...

To find the Fermi energy I need to find the electron density of the material and that I can do by finding the density of atoms in the material in some instances this same density. From what I gather it's not always that way Sometimes you have to multiply a certain number For example...

Homework Statement It is just a line of equation from my Stat Mech textbook, that says B = -V(dp)/(dV) = (10U)/(9V) = (2nEf)/3 where B is the bulk modulus, V is the volume, p is the pressure, U is the energy, n is the number per unit volume and Ef is the fermi energy. Homework...

Problem statement: Determine electron and hole concentrations in Si at room temperature given that the Fermi level is 0.20eV above the valence band energy. So my thoughts on this problem: First we draw the band diagram, and it's clear that this is P type. Then, p0 = Nv * exp((Ef - Ev)/KT)...

Quick Fermi Energy Question..Free electrons?? A quick question on the Fermi energy. From a 3D cubic well, one can derive an expression for the Fermi energy of a solid: Ef = h^2/2m . (3.pi^2.N/V)^2/3 Now, I have come across an expression where N/V, electrons per volume, is replaced by...

Homework Statement The degeneracy of the nth level above the ground state for a three dimensional harmonic oscillator is (n+1)(n+2)/2 where n takes values n=0,1,2,... A gas of N non-interacting identical lithium atoms (mass 6amu) each having spin1/2 is confined in a 3d harmonic potential...

Si is doped with 6 x 1015 cm-3 donors and 2 x 1015 cm-3 acceptors. Find the position of the Fermi level with respect to Ei at 300 K. i know the equations are (for n-type) EF = kT ln(ND/ni) + Ei (for p-type) EF = kT ln(ni/NA) + Ei however, since the problem gives me both donors and...

Homework Statement "The numerator of this fraction: \overline{E}=\frac{\int \! E N(E)D(E)dE}{\int \! N(E)D(E)dE} (N(E) is the number of particles in an energy state, D(E) is the density of states) is the total (as opposed to the average particle) energy, which we'll call U_{total} here...

Hi again! another question! I statistical mechnics by Pathria, it has all about the fermi gas in a magnetic field in chapter8 I have another question what if the electron was in some boundaries? what would change then about magnetization of grand partition function? For example for an...

For a perturbation that is constant within a given time, we can use Fermi's Golden Rule. In developing Fermi's Golden Rule, 2 approximations are made: (1) The energy interval E (continuum) to which discrete states are scattered is small enough such that the density of states is constant...

Note: I already asked this question ion the introductory physics forums but have had no replies. The question I'm being asked is: If the Fermi level of copper is 7eV calculate the magnitude of the Fermi wavevector?The formula I'm pretty sure it goes with is Kf=(3pi^2ne)^2/3 The reason I'm...

For those not familiar with the term Fermi estimate/problem/question see here: http://www.vendian.org/envelope/dir0/fermi_questions.html http://en.wikipedia.org/wiki/Fermi_problem My question: Between the time that Riemann posed his famous question (in 1859) and now, how many hours have...