Fermi Definition and 336 Threads

The attached jpeg shows Enrico Fermi at the blackboard. There is a geometric drawing and some math I do not understand. Can you point me in the right direction? I have searched for a discussion of what he is presenting but cannot find one. The photo may be familiar because it was...

Hi, everyone. I'm learning basic theories about semiconductors but can't quite understand the concept of Fermi level. is this just a imaginary energy level or true existence? and why Fermi level is close to the conduction band of n-type semiconductor and valence band of p-type semiconductor...

Hello, I have read several articles/websites which talk about modelling white dwarfs, In all of these papers they state that it can be assumed the electrons have temperature zero, i.e. T<<T_fermi. I haven't been able to find a solid explanation of why this is approximation is possible...

Hi! So I'm a bit confused: first off, does Fermi liquid theory have "order". I suppose it depends on how you define order. But in case it does, is it described by symmetry breaking? From what I read, I think it does have order which is not described by symmetry breaking. But then I have...

Homework Statement what is the probability of finding an electron with energy between 5eV and 5.5eV at T=300k, given that the fermi energy of the metal is 4.2 eV. Homework Equations ##P(E,T)dE= \frac{3}{2} E_F^\frac {-3}{2} \frac{E^\frac{1}{2}}{e^\frac{E-E_F}{K_B T}+1}dE## The...

Suppose there is a semiconductor with Fermi energy $E_f$ and that there are $N$ bound electron states. I'd like to know why the mean number of excited electrons takes the form \bar n(T)={N\over \exp\beta(\mu-E_f)+1} where \mu is the chemical potential. ____ I can see that the Fermi...

Hi all, Why do the fermi level for electrons and holes coincide in equilibrium condition and why they separate as quasi fermi levels in non equilibrium situation?

How is it that the calculated Fermi energy of neutrons and protons in a heavy nucleus are different, but it's observed that they have the same energy? And how much is the Coulumb repulsion of the protons play a factor in that?

I know this is true under thermal equilibrium, but I am not sure why. Why can't the Fermi level be a function of position relative to the pn-junction? How does that follow from thermodynamics/statistical mechanics?

The density of states at the fermi energy is given by D(E_F)=(3/2)n/E_F I understand the density of states is the number of states per energy per unity volume, accounting for n/E_F. I don't understand how the 3/2 multiplying factor accounts for the volume?

edit* never mind figured it out thanks.

Homework Statement Here g(ε_f) is the density of levels at the Fermi energy and T is the temperature. Calculate the specific heat of the electron gas in potassium (K) treating it as a free gas. For a free gas the density of electrons at ε_f is: g(ε_f)=(3/2)(n/E_f) where n is the electron...

Hello! I have a small question, and I am not sure if I am missing something: Today I glanced at the wikipedia page for Pions, and saw this: Statistics: Bosonic Can anyone explain to me why a quark paired with a anti-quark obey Bose-Einstein Statistics? If quarks obey Fermi-Dirac statistics...

Hey, My question is displayed below I have had a few questions like these and I just want to check my approach is correct, but I'm not sure - I know that the Fermi Energy of Cu is something like 7eV. Now we are told that there are 4 atoms per cube side - meaning 8 atoms but cubic...

Hey I have a question pictured below: I always seem to struggle with questions like these, my understanding is we know the spacing of K-states throughout the lattice is given by \frac{2\pi}{L} Such that the fermi wavevector divided by this spacing and multiplied by 2 due to the fact...

1. How many sands on the earth? 2. Hints: Using the Fermi estimation 3.

i'm reading through halzen and martin's chapter 12 on the weak interaction which they calculate the fermi coupling constant form oxygen beta decay using \Gamma = 1/\tau = G^2E_0^5/30\pi^3 with E_0 = 1.81MeV and \tau log 2 = 71 sec. they get G\approx 10^{-5}/m^2_N. where m_N is the nucleon mass...

I Know that the fermi level in an intrinsic semiconductor is found between the valency level and the conduction level in the energy gap , and I know that also when the semiconductor is doped the fermi level either move toward the conduction band or away from it.But actually I can not get the...

I have searched a lot on the internet for a simple explanation of these two terms. As I have understood these things (quantum physics), after reading from a lot of sources, is that in an atom there are discrete energy levels and electrons occupy the levels according to the least energy of the...

The intrinsic semiconductor Fermi level is the maximum energy level an electron can be in at 0K. Or Fermi level is a level where there is a probability of 50% to find electrons at any temperature. Conduction band is a range of energy where electrons freed from bonding stay. Valence band is...

Homework Statement The density of gold (atomic mass 197) is 19.32 g/cm3. Assuming each gold atom contributes one electron to the free electron Fermi gas, calculate the Fermi energy in eV. Homework Equations Fermi energy is given by: E_F=\frac{h^2}{8m_e} \left( \frac{3N}{\pi V} \right)^{2/3}...

Hello! I've just started reading about quantum mechanics, so my question may sound silly. I'm using the book of physics of Paul Tipler. It's says that inside the metals we have a lot of free electrons, like a electrons cloud (like when we learn in the School). These electrons follow the...

Why does the Fermi level level drop with increase in temperature for a n type semiconductor.? What's the basic idea behind Fermi level? How does it get affected by temprature?

Hi everyone, Defined the Fermi Normal Coordinates (which can be seen for example http://relativity.livingreviews.org/open?pubNo=lrr-2011-7&amp;page=articlese10.html" ) is there any heuristic argument to explain why the area element is something proportional to the element of solid angle? I...

Based on Fermi distribution, if there are two electron energy levels with occupation possibility of ¼ and ¾, respectively, calculate energy difference between these two levels.

I read somewhere that the error incurred from approximating the Fermi surface to be a sphere in k-space goes as 1/N where N is the number of electrons. So, N is generally of the order 10^23. I couldn't figure out how they came up with the value. I was trying to say that the actual shape of the...

As we know that the properties of nanoscale material are quite diffrent from the bulk's. But what's the threshold of the size, or what the upper limmit where significant difference can be observed? The De Broglie wavelength or the Fermi wavelength of the electron in material? How to understand that?

The fermi four point interaction (consider its modern version, quark up to down plus electron plus antineutrino) is not renormalisable Then we introduce an intermediate boson W in the middle. Then we give mass to this W using the higgs mechanism. Then we produce the higgs via a fermion...

As we know, in intrinsic semiconductors the fermi level is halfway between the valence and conduction band. and The fermi level is the level in which the most energetic electron settles at T=0. but my question: How can the fermi level be in a forbidden region in intrinsic semiconductors? or...

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...

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...

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...

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=...