Fermi Definition and 336 Threads

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.

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?

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 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.

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...

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...

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...

Can someone give me a clear, nonambiguous definition of the fermi level in a semiconductor? Is it the energy of the highest occupied state, the chemical potential at T=0 or what? I don't think it is the first since the fermi level is typically put midway between the conduction and valence band...

Homework Statement [/B] Five free electrons exist in a three-dimensional infinite potential well with all three widths equal to a 12 angstroms. Determine the Fermi energy level at T 0 K. Homework Equations E = [(h_bar*pi)2/(2*m*a2)]*(nx2 + ny2 + nz2) The Attempt at a Solution Tried using EF...

Normally, you think about SM forces being conveyed by gluons, weak force gauge bosons, or photons (ignore that troublesome gravity thing for the moment) between point particles. There is also a property of fermions (particles with total angular momentum Q=1/2, 3/2, etc.) that they can't occupy...

Also is it better than doing research with professor in school? If you had to choose

I know we can shift the fermi level by doping the material with other elements. In case of semiconductors doping with the pentavalent or trivalent will change the fermi level. But my question is ''can we shift the fermi level, without altering the position of valence band and conduction band?"...

I encounter contradictive informations about this issue which is supposed to define "real noble metals" is this statement correct at absolute zero or at any temperature? Does it include ds hybridizations?

Today's APOD shows an animated visualization of a gamma ray flare detected by The Fermi Space Telescope. The video says, "each circle represents one gamma ray" That language suggests single photon detection. Is that correct?

Why can not the density of states of a metal at Fermi level be zero? Thanks!

Hi all, I recently installed ubuntu on my pc and I am trying to run the Fermi software provided by NASA (http://fermi.gsfc.nasa.gov/ssc/data/analysis/software/). I believe I did all the installation steps right but I am having trouble starting the software. If you are familiar with this...

Hi, a question please: Do all metallic substances have an equal Fermi energy level (at a constant T) ? If not, what will happen (before equilibrium) if one "fuses" together two bulks of metal with different Fermi levels (as in a PN junction) ? Since there's an abundance of energy states...

Do we have Bose like and Fermi like particles (fields) in 1+1 dimensional spacetime, Fermi like particles (fields) that obey the Pauli Exclusion Principle? For what space dimensions does the Pauli Exclusion Principle operate? Thanks for any help!