Fermi Definition and 384 Threads

Since for a general contravariant vector, ##\nabla_{\nu}V^{\mu}## will not in general be zero, is it correct to say that all of them are transported by Fermi Transport? (With the only vector being parallel transported being the four velocity vector?)

Where is the electron-nucleon interaction? On the surface of the nucleus, or at the origin (R-0) ?

I think that this is a relatively easy question (no equations) however I cannot seem to find anything on it. "For which specific class of decay is only the Fermi decay mode possible?" I know Fermi decay is ∆S=0 and therefore ∆J=0 type of decay

Do Fermi and Gamow-Teller transitions only refer to changes in isospin , as in beta decay and orbital electron capture

Here is a simplification of a problem given in my book. I don't get the simplification part. Could you please help at this ? It seems book has done the calculation wrongly.

Hello, I have got a question regarding Wick contractions. At lectures, we wrote that only a_i a_j^{\dagger} contracted gives Kronecker delta \delta_{ij}, other creation anihillation combination of operators gives just 0. But, when we did an exercise, we computed in Fermi sea: \langle...

Homework Statement Let's consider conduction electrons (at T=0K) that are put in a magnetic field. The electrons can have spin that is parallel or antiparallel to the magnetic field. Below is the density of occupied states for such a system (horizontally) as a function of energy (vertically)...

Homework Statement The conduction band of a hypothetical crystal of one-dimensional Cesium reticular with step a=300 pm (1 atom per cell) is characterized by the ε dispersion law ##\epsilon (k) = V_0 + \frac{\hbar^2}{m_e}(\frac{1}{2}k^2 - \frac{a}{3\pi}|k|^3## where ##V_0 = -4 eV##, is set so...

Where does the fermi level lie at? I have an understanding that at absolute zero it would be lying halfway the band gap. Shouldn't it be lying at the top part of the valence band?

This is schematic band structure for the dxz and dyz orbitals using a 2D square Fe lattice. What is the location in the Brillouin zone of the hole-like Fermi surface and the electron-like Fermi surface?

How exactly does hydrostatic pressure affect the shape and size of each Fermi surface in Figure 4B? How do you read this figure or what exactly is it showing?

Homework Statement We are asked to derive the expression for the internal energy of an ideal Fermi degenerate gas using Sommerfeld expansions, writing out terms up to the fourth order in ##(\frac{T}{T_F} )## , that is, we must determine ## \alpha ## in the following expression: $$ U=...

I'm having a hard time understanding the mechanism of J coupling in NMR. Why is coupling information only transmitted through bonding electrons with nonzero s-character? For example, why can't coupling information be transmitted through a bond with no s-character, e.g. a retrodative bond...

Homework Statement The energy band for two different metals can be expressed as E=Ak2 and E=Bk2, respectively. Suppose A>B, and the Fermi energy is equal for these two metal. Calculate and compare the Fermi velocity for both metals. Homework EquationsThe Attempt at a Solution I'm very confused...

Hi, I have started looking at the fermi level and how it relates to the behaviour of conductors. It is my understanding from what I have read that the fermi level is the top of the fermi sea of filled energy states when the material is at T = 0K. 1) Is the fermi level inside the conduction...

In a degenerate n type semiconductor, when the doping concentration has a gradient(say -ve gradient), then how fermi energy level and intrinsic Fermi energy levels will depend upon the concentration gradient? ~If anyone knows anything about it, kindly help.

The problem: A simple cubic metal has an electron density such that the Fermi energy just touches the edge of the first Brillouin zone. Calculate the number of conduction electrons per atom for this condition to be fulfilled. The attempt at a solution: I know that the electron density for a...

"The Fermi paradox or Fermi's paradox, named after physicist Enrico Fermi, is the apparent contradiction between the lack of evidence and high probability estimates, e.g. those given by the Drake equation, for the existence of extraterrestrial civilizations". I have always failed to understand...

Homework Statement Working through problems in Mahan's 'Many Particle Physics' book, and at the end of the 1st chapter there's a question where we're asked to consider a fermion system with three energy states with eigenvalues E1, E2, E3, and matrix elements M12, M23, M13 which connect them and...

Hi, I was hoping I could get some things cleared up. Recently my Solid State professor mentioned that we could simply, from the chemical formula, predict where the band crossings are going to be. For example, take LaFeAsO. Since La has a valency of +3, Fe of +3, As of -3, and O of -2, he...

Hi dear friends Please reffer to my work , I did part ( a ) Can someone help me to solve part( b ) Please

Hi dear friends Please reffer to my work , I did part ( a ) only Could you please help me to do part ( b ) I don't know how to do it.

Homework Statement Hi all, This is Kittel 9.2. This problem has been asked about before, but the people asking found solutions. I'm trying to find the free electron Fermi radius for a 2D metal with a rectangular primitive cell (a = 2 Ang, b = 4 Ang). Homework Equations Please forgive my...

We are doing spectroscopy on some semiconductors covered by a layer of Aluminium. My professor says it might be a challenge for to see the valence band structure of the semiconductor because the metal has a high density of states at the fermi level. Does this make sense to you? Does a metal have...

My teacher told me the other day that a semiconductor does not have a fermi surface. I didn't understand this remark. As I understand it the Fermi Surface is just the surface in k-space spanned by the highest occupied energy levels. Surely in a semiconductor you will also have some highest...

I am reading about angle-resovled-photoemission-spectroscopy (ARPES). It seems that it is a technique that gives the energy dispersion as a function of the momentum k. However in all talks about it, it seems to be a technique that gives us the fermi surface of the given structure. I don't...

Hello! Let E_1, E_2, \ldots, E_n be n allowed energy levels for a system of electrons. This system can be described by the Fermi-Dirac distribution f(E). Each of those levels can be occupied by two electrons if they have opposite spins. Suppose that E_1, E_2, \ldots, E_n are such that...

Hello! In order to obtain the number of actual electrons in the conduction band or in a range of energies, two functions are needed: 1) the density of states for electrons in conduction band, that is the function g_c(E); 2) the Fermi probability distribution f(E) for the material at its...

Hello, A question I can't seem to find a simple answer to is, what happens to the Fermi-Dirac distribution at T grows large? Mathematics suggests that it approaches 1/2, like it does when the energy becomes equal to the Fermi energy. Or, are we not allowed to use the F-D distribution for high...

Hello! When computing the density of states of electrons in a lattice, a material with dimensions L_x, L_y, L_z can be considered. The allowed \mathbf{k} vectors will have components k_x = \displaystyle \frac{\pi}{L_x}p k_y = \displaystyle \frac{\pi}{L_y}q k_z = \displaystyle \frac{\pi}{L_z}r...

Homework Statement This isn't really a homework question but I didn't know where to put it. Homework Equations ##E_f = \frac{h^2 k_f^2}{2m}## ##k_f = (3 \pi^2n)^{\frac{1}{3}}## The Attempt at a Solution I'm going through a lot of examples and every time I punch the numbers in I get an...

Hi guys, So If any of you aren't familiar with the Fermi Paradox, I highly advise you read about it. It is easily one of the most interesting topics I've come across. IF you can't be bothered for this I have included a small summary of what the Fermi Paradox in my survey (see below). I'm doing...

I'm practicing for the Physics GRE, and came across a question that has me stumped. "In elementary nuclear physics, we learn about the Fermi gas model of the nucleus. The Fermi energy for normal nuclear density (ρ0) is 38.4 MeV. Suppose that the nucleus is compressed, for example in a heavy ion...

Hello, This problem is about cooper pair formation and what happens with the calculations if there is an attractive potential between electrons but it is not in the presence of a filled fermi surface. 1. Homework Statement Two electrons just above the filled Fermi Surface of a material can...

Please explain me. I don't understand what is quasi fermi level f(E) and fermi energy Ef. For example (GaAs) at the room temperature (T=300K) Eg = 1.42 eV; (energy band gap) mc = 0.067 me; (effective mass of electron in conduction band) mv = 0.45 me; (effective mass of hole in valance band) kT =...

Homework Statement In the book "In searcg of life in the Universe" A.D. Ursula gave the following formula R1/C1 = R2/C2 (A) when the contact between two civilizations happens, where R - result from a contact and C - cost to make a contact for those civilizations. Homework Equations The key...

why does work function measured from fermi level while work function is defined by lowest energy required to remove an electron from surface of materials and fermi level the level have 50% chance to occupation that's mean there is level above it have electron inside so why we don't measure...

what i mean exactly what is the position of Fermi energy for semi conductor materials 1- at the highest of valance band 2- at the mid-way in energy gap like Fermi level at 0 K

Hi people, I don't understand why when we apply the electric field to the metal Ef remains the same. Ef as translation energy of electrons remains the same but we accelerate the electrons with applied electric field so the translation energy increases too? In other hand according the formula...

Namely, are the wave functions of electrons near the Fermi surface spatially distributed in the so-called "active blocks" (CuO2 layers and etc.) or in the so-called "charge reservoir blocks" ? Or any other case? ( EO/(AOx)m/EO with m =1, 2 monolayers of a quite arbitrary oxide AOx(A = Bi, Pb...

Fermi-Dirac distribution function is given by f(E)=(1)/(Aexp{E/k_{B}T}+1) here A is the normalization constant? How we can get A? E is the energy, k_{B} is the Boltzmann constant and T is the temperature. thank you

I have some qualitative questions about the relation between band structure, density of states, and Fermi energy (or Fermi level). 1) Say you have a given electronic band structure (energy as a function of k) obtained by any method. How do you relate this to the Fermi energy (or Fermi level) ...

Homework Statement I was to calculate the Fermi Wave Vector $K_F$ for a metallic structure then explain why the nearly free elctron model is consistent with its behaviour?The Attempt at a Solution After calculating the wave vector, I see that the fermi wave vector is within an energy band...

Homework Statement This isn't actually a homework question, but in my semiconductors textbook, the following equation has been given: E_f = E_g - k_BTln(\frac{n_0}{N_d - N_a}) This is for the limiting case Nd>Na>0. I got a little confused as to where that equation has come from. Homework...

(1) (2)(3) (4) (5) we can find Equation (5) by dividing po by n0, and write an equation with respect to Ei. However since equation (3) is a special form of (1) and (2), [when Ef=Ei] we can obtain equation (5) from any arbitrary Ef. However, since eq (5) consists of constants only, it will...

http://ecee.colorado.edu/~bart/book/book/chapter2/ch2_6.htm#2_6_2 equation (2.6.24) we have this equation for fermi level, but I wonder how this works though? In the lecture, we assumed Ec=Eg and Ev=0 to get E_gap/2. but I wonder how (Ec+Ev)/2 actually gives E_gap/2 instead of Ec-Ev=Eg

Consider the Lindhard response function: \chi(\vec{q})=\int\frac{d\vec{k}}{(2\pi)^d}\frac{f_\vec{k}-f_{\vec{k}+\vec{q}}}{\epsilon_\vec{k}-\epsilon_{\vec{k}+\vec{q}}} where ##\vec{q}## is the wavevector, ##\epsilon## is the free electron energy and ##f## is Fermi-Dirac distribution function. For...

hi every body question is : Consider that 5.5E22 free electrons are confined in a potential barrier of length 3.2A . find its Fermi energy ?the main point is that i was confident about the answer of question .. but the doctor said it is wrong .. he said i should use the relation between the...

Homework Statement Find the densities of states 0.08 eV above the conduction band edge and 0.08 eV below the valence band edge for germanium. Find the volume density of states (i.e. number of states per unit volume) with energies between the conduction band edge and 0.4 eV above the conduction...

Homework Statement Part 1) Use the fermi dirac probability function for t=150k, t=300k, and t=600k to fill in the table below. Part 2) Also show a sample calculation for (e-ef)=0.06eV and T=300k. Part 3)(Same as part 2?) Calculate the probabilities of a state at E -EF =0.06 eV being empty for...