What is Band: Definition and 531 Discussions

I want to plot band structure silicene in the following path: Γ→M→K→Γ Do the following equation for the above path is correct: close all clear all clc aa=2.28; a=3.86; a1=(a/2)*[sqrt(3),-1,0]; a2=(a/2)*[sqrt(3),1,0]; b1y=-(2*pi)/a; b1x=(2*pi)/(sqrt(3)*a); b2x=b1x; b2y=-b1y; %K-point pKx =...

This 400-700nm slice is the Photosynthetically Active Radiation (PAR) required of plants and, for many applications, there is much unwanted UV and IR heat outside of it. Is there any known translucent material or film that will pass a high % of that 400-700nm wavelength from sunlight while also...

I am having a hard time understanding flat band voltage in MOS capacitor. Please see the picture below about MOS capacitor. Q0 is a fixed effective charge at the surface between oxide and semiconductor and it is positive here. The voltage across the oxide caused by the fixed charge ψox =...

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...

The standard approach to explaining band structure is to assume that the electrons in a solid move in a potential from the ions, which is periodic leading to Blochs Theorem and the formation of band structure. But I am a bit confused at this point. Is the approach only valid for the valence...

if we solve elliptic integrals related to doped graphene, band gap does not occur. But actually it occures with p doping. How can I solve this puzzle? Thanks for any help.

Do all electrons orbit in the ground state, when the band gap, is increased, or decreased, as atoms come together to form molecules.? Like in glass, transparent liquids, and plastics. As atoms come together to form glass, like silicon, sodium, and calcium. Do the electrons orbital permanently...

In band theory, one of the first things that is always stated is that a completely filled band, such as the valence band at low temperatures, will not contribute any current because the average velocity will equal zero. This is usually justified by showing a plot of a parabolic bandstructure...

hi, Initially, I know how to take surface integral of möbius band via given parameterization, but I really wonder how these parameters are created. How can we derive these parameters ?? What is the logic of deriving such a good parameters?? Could you give some proofs??

Hi everyone How can I determine the optical band gap of a cobalt ferrite film deposited on a glass substrate using its absorption, transmittance and diffuse reflectance spectrum (knowing that I don't know the thickness of this film)

I know that orbital angular momentum is quantized. If the potential energy is developed because of the external magnetic field applying a torque on the magnetic dipole, then from the dot product of the dipole moment and magnetic field we have a cosine term, shouldn't this give rise to all the...

Hello! Double heterostructures are used in LEDs and lasers to provide both the confinement of the charge carriers and the confinement of the generated light. This image is a comparison between a homojunction and a heterojunction. As regards the unbiased junctions, when the n region and the p...

Hi. I've set myself a project with a couple of my classmates and despite the impracticability of it we want to do it as well as possible. Our aim is to look at using a massive elastic band in order to launch a payload at massive velocities, possibly even at escape velocity. To this end I've...

What do we mean by break points in band structure ? and what that sentence means : "if the band index were chosen in such a way that the energies are indexed in ascending order for any k then break points would appear in the εnk vs. k plot (with n fixed) wherever two lines intersect." ...

Hello, I am trying to figure out the width of bands in a 1-dimensional lattice. Here is a short derivation from the book I am reading: if we approximate the free electrons as being in a square well then the energy levels are ## \frac{\pi^2 \hbar^2 n^2}{2mL^2}##. If there are ##N## ions...

Hello PF! I have a project/competition in freshman college Aerospace that calls for a plane that can stay in the air for as long a time as possible while going as far as possible. The requirements don't explicitly say we need rubber bands as a propulsion but pretty much prohibit everything but...

Homework Statement I need to explain for a lab, why the efficiency of a rubber band slingshot constant for different stretch lengths. I don't need math, just a general explanation of why kinetic energy of projectile/elastic potential energy in rubber band is constant. Homework EquationsThe...

Homework Statement Hi, I just need some confirmation on 3 questions H(s) = 1/(s+1)^2 1. I was asked to calculate the poles and zeros. I believe zeros: none poles: 2 (or p1,2) = -1 2. I was also asked to calculate the slope of the magnitude response was w -> 0 Here is my sketched graph...

Homework Statement Homework Equations $$ Z(1) = \sum_{i=1}^{} e^{\frac{E_i}{K_bT}} $$ where ##E_i## is each of the possible energy states available to a single link (in this case the right and the left states). $$ P=\frac{\sum_{i=1}^{} e^{\frac{E_i}{K_bT}}}{Z} $$ The Attempt at a Solution...

I was trying to determine the bandgap in the nearly free electron model. I'm having trouble to determine the band gap bewteen the second and the third band. Its a one dimensional problem. So, the central equation reads: ##\displaystyle \left [ \frac{\hbar}{2m} (k-G)^2-E \right ]c_{k-G}+...

-iation. Could the opacity of a material to one band of EM radiation (light) could be altered by irradiating the material with another band of EM radiation (X rays)? I think you are suggesting that: By raising the electrons in the atoms to higher energy bands (with the X rays), so that they will...

I am doing an experiment where we have to use the threshold voltage of LEDs to determine Planck's constant given the following relation $$ eV_0 = E_g = \frac{hc}{\lambda} $$ where ## V_0 ## is the threshold voltage, ## \lambda ## is the wavelength of emitted light and ## E_g ## is the band...

Hi there people! So my question is why you can see localized surface states within the band gap of the material with an STM. How is a tunneling circuit being established?

Hi, How can I prove direct band gap property of a Transition Metal Dichalcogenide electrically and optically through experimentation? I can use PL measurements to prove this for optical band gap. Is there any other equipment or technique to prove this? I can not use ARPES because channel length...

Hi all, I'm currently trying to investigate the edge current on a finite strip of Zigzag Haldane model (spinless, pi/2 phase) and I measure the current (in my code) by taking the expectation value of my current operator which is a function of wavevector k, for each eigenvector of the...

I'm teaching myself how to do DFT for my master's project, where I want to use it for calculating band structures for different heterostructures. Now to learn DFT I am on one hand reading a book on the basic theory, on the other hand using different freeware packages to try and calculate the...

Homework Statement Find band gaps for Dirac Comb potential $$V = \sum_n aV_0(x-na) $$ Homework Equations Bloch Theorem $$\psi(x+a) = e^{ika}\psi(x)$$ The Attempt at a Solution I can solve exactly up to $$\cos(k a) = \cos(\kappa a) + \frac{2ma^2V_0}{\hbar^2}\frac{\sin(\kappa a)}{\kappa a} =...

Homework Statement See picture attached Homework Equations Graph based question The Attempt at a Solution So I was looking at an example and I wanted to know how this energy band diagram was drawn from the picture. As the x increased the doping level decreased, but how can I know if it will...

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) ...

Is there any method for how to choose k-points in band structure calculations for aluminium slab 5*5*4 can somebody help in this question? Thanks

Homework Statement I am running CASTEP DFT software to simulate pristine graphene, and am unsuccessful in obtaining the trademark zero band gap at the k-point as reported in numerous papers to date. Any assistance would be greatly appreciated as the subject is very new but I am keen to push...

Homework Statement Nobel prize for physics for blue laser diode using Gallium Nitride with band gap of 3.4 eV and a refractive index of 2.429. Explain how these parameters determine at what wavelength a Gallium Nitride semiconductor will laser at. Homework Equations E=\frac{hc}{\lambda}...

Do electrons in conduction band are only responsible for current? Don't the electrons in partially filled valence band capable of moving contribute to current? Material discussed-metals(conductors)

Hi I have been drawing pi bands, silicon nanoribbons. But I can't draw sigma bands. Can help me for plotting sigma bands, silicon nanoribbons in Matlab.

I almost "get" it, but not quite. Can someone help? Here is my current understanding. Say you solve the Kronig-Penny model. You find that you get bands of N closely spaced energy levels, with large gaps between them. Under normal conditions, electrons fill the band to some level (let's say we...

Consider the figure from section "Electrical conductivity":https://en.wikipedia.org/wiki/Valence_and_conduction_bands I understand that below the Fermi level, we have bands of allowed energy separated by band gaps. Then, we have the Fermi level. Then we have the conduction band. My question...

Hello, I'm trying to analyze the following system to get some idea about the forces present. The red line is supposed to represent the belt wrapped around the two drums. There is an extra part to the belt, however. Tangentially from the drum, a part of the string is attached to an unmovable...

I attached a picture. In the first figure, we see that the difference between bands is rather large. We see that electrons do not occupy all the energy levels from energy 0 to Fermi energy level. There are forbidden band gaps. But in the second figure, I see that the electrons occupy...

Hi! I'm sung dae with tensile strain, energy band structure could be changed. bang gap decrease with compressive strain, energy band structure could be changed. bang gap increase but I'm not sure why it could be changed .. Is there someone who explain in detail ? thanks. have a nice day! :)

Do any band structure (in absence of any external field) in general, is symmetric with respect to k? In other words, do we always have E(k)=E(-k).

I recently read about the recommended amount of exposure time to high sound volumes: http://www.dangerousdecibels.org/education/information-center/decibel-exposure-time-guidelines/. Since I am in the Band at school I was somewhat concerned about if the sound intensity would be too much...

What exactly is the relation between these 3 quantities? As far as I can tell the work function is the energy needed to bring an electron from the fermi level out into vacuum, while affinity is from the bottom of the conduction band. Does this then mean that they can be used to calculate the...

Homework Statement From the experiment I did my force was equal to 0.0686N +/- 0.00196N and my x (rubber band stretch) was equal to 0.003m +/-0.002. The question asks to determine the force constant k +/- ∆k. Homework Equations F = kx k = F/x ∆k = |k| ∆x/x +∆y/y The Attempt at a Solution k...

The abstract of this paper ( http://www.sciencemag.org/content/297/5588/1853 ) says "The electronic properties of the one-dimensional chains are dominated by an unoccupied electron band" I'm not sure what the paper is referring to by an unoccupied electron band. Wouldn't a metal be described...

Who can help me in writing the following program: phase(i) = exp(1i*dot(k(:,index),R(:,i))) This gives you the phase you're going to multiply with the hopping parameter. You'd have to write a loop that runs from i = 1:3 in order to multiply each contribution to the hopping parameter such that...

if in a solid there arent no states with same energy then why energy band vs location diagram is flat?

Why is the conduction band state s-type and the corresponding valence band state p-type?

This was given as a problem in a calculus textbook I'm working through (apologies if this should have gone in the physics forum) 1. Homework Statement An ant crawls at 1foot/second along a rubber band whose original length is 2 feet. The band is being stretched at 1 foot/second by pulling the...

Can anybody explain my what is the origin of this forbidden gap? I mean how it was created and what is the physics behind this issue?

Dear forum people I consider four atomic orbitals of the silicon atom: s, px , py and pz , thus Hi,j is a 4*4 matrix. Hi,i is the expression of the diagonal matrix and Hi,j is the expression off-diagonal matrix where the expression for Hi,i and Hi,j is attached. But I can not calculate the...