Band Definition and 531 Threads

Dear all, I have been thinking, if insulators have their valence band filled, then which band does the extra electrons go when it is negatively charged?? If it is the conduction band, then it would become a conductor... Similarly, if it is positively charged, there would be a hold in the...

Hi! I'm new here... I'm going to go right to the point. I know that when you take atoms and get them closer together, the discrete energy levels turn into bands. But when I'm facing a band structure plot, such as this one (band structure of aluminum nitride in wurtzite structure)...

Hey guys! This is my first post here, and the main reason I signed up. I need a physics-y, kind of geeky band name. I was using Neon Black but there's another band by that name already. I also thought of naming the band Bigger Than Infinity but that sounds weird. Quantum...

This seems like a straightforward thing but no textbook I've seen addresses it. Take the direct gap semiconductors GaAs (band gap 1.42 eV) and InAs (band gap 0.42 eV). If these two were alloyed together, would the band gap become some sort of average between the two values? As an example, say...

sorry i moved it to correct forum i rushed in, in my panic

Hi! I'm new to the physics forum but I've read a little bit and I'm impressed with the knowledge a lot of people have here. I've tried searching for any topic on my question without any luck. My question is simply what the algorithm is to determine the band structure for a one dimensional...

Hi, I have a very basic question on formation of valance and conduction band. It is said that conduction band is above the valance band. So In a hypothetical lithium molecule formation(for example purpose) : If 100 Lithium atoms combine together, then 1S shell is split into 100 1S shells (one...

For a direct sum of Mobius band, it is trivial if it has two linear independent nonvanishing sections. I have the following as my sections： s1=(E^(i*theta), (Cos(theta/2), Sin(theta/2)) s2=(E^(i*theta), (-Sin(theta/2), Cos(theta/2)) Clearly, the above sections are linearly independent and...

Hi, I have porblem in visualizing or imagining the formation conduction and valance band in basic semiconductor physics. Most of the books explains as ' when millions of atom combine together the outermost shell and subshells gets altered and form more energy levels for electrons to occupy. and...

Hi, Could someone help to explain that why for the 2 D system, like 2 dimensional electronic gas, the crystal momentum k in 2D band structure is defined on a torus? Thanks a lot.:)

I have a serious doubt about the concept of band theory of solids. While explaining the behaviour of semi conductors, the following explanation is given. "The valency bands are completely filled electron-bands, where as the conduction band is usually empty. The conduction takes place when a...

Homework Statement Glass is transparent to visibile light under normal conditions; however, at extremely high intensities, glass will absorb most of the light incident upon it. This works through a process known as multiphoton absorption. In this process, several photons are absorbed at the...

Homework Statement have band dispersion \epsilon = \epsilon_c + \frac{h^2 k_x^2}{2 m_x} + \frac{h^2 k_y^2}{2 m_y} + \frac{h^2 k_z^2}{2 m_z} Show density of states is g(\epsilon) = \frac{m^{3/2}}{\pi^2 h^2} \sqrt{2|\epsilon - \epsilon_c|} Homework Equations 2 \frac{d\vec{k}}{(2\pi)^3} =...

Dear all, I want to calculate the band structure of graphene for a unit cell with 8 atoms in the Tight Binding approximation. There is no problem about drawing the band structure for a unit cell with 2 atoms. But by increasing the unit cell size, first brillouin decrease and there is a gap in...

Hi all, I'm currently trying to learn more about photonic band gaps. The material I am looking at is an FCC crystal of spheres with an (111) surface, and this structure is theoretically predicted to display an incomplete band gap from the gamma to L points. (Please see attachment)...

Homework Statement I'm trying to write up my physics lab but i don't know how to calculate the spectral band width. Homework Equations The Attempt at a Solution I measured a coherence length for green light (546.1nm) to be 0.122mm. How do I calculate band width from this...

Homework Statement In class we studied a phase transition in a model of a rubber band. For small applied tensions, f < f^*, the Helmholtz free energy of the band as a function of the length is A_1(L) = (\kappa_1 /2)L^2, while at large applied tensions, f > f^*, it is A_2(L) = (\kappa_2 /2)L^2...

Homework Statement Consider a rubber band for which the tension, f, as a function of temperature T and length L is f = \kappa T (L+\gamma L^2), where \kappa and \gamma are positive constants. Determine the heat flow between it and its surroundings when the rubber band is stretched reversibly...

indirect band gap semiconductor doubt its said that indirect band gap semiconductors like silicon and germanium are not used as a light sources because they have more non-radiative recombinations rather than radiative ,which inturn decreases efficiency of optical source. but i want to...

what is the practical use of the concept of band gap other than classification between material? can free carrier absorption be manipulated by changing band gaps?

I was wondering that how the knowledge o transmittance and reflectance curves can give us information about the band gap and electronic structure of a metal? How these curve differ for semiconductors? I desperately tried to extract n, k values from the reflectance curve of a nitride material...

okay guys I've been looking for ages and i just can't find anything that will help me with finding a distance that will be travel by a rubber band powered car. I've been playing around with kinetic energy= potential energy but i can't seem to get anywhere. Any help will be greatly appreciated...

Hey I was studying for my test, in my notes it says si cannot be used for led, because it has indirect band gap.Why indrect band gap is not useful for led?

Homework Statement Given: K=17, R1=R2=6,247 Ohm Calculate the value of C1=C2=C to set the center frequency of the filter to 17.3 kHz.Homework Equations w0 = 1/[C*sqr(Rth*KR2)] from lecture notes R1=RthThe Attempt at a Solution w0 = 1/[C*sqr(Rth*K*R2)] C= 1/[w0*sqr(Rth*K*R2)] C=...

how the conduction band offset varies with Al concentration?? what is the different?

Homework Statement 1) I try to understand the lorentzian lineshape and relate to the gaussian graph but i don't know what is the difference. 2) Uncertainty principle- if it's related to the lorentzian lineshape it will give the information about the lifetime in the well and the width of...

Does anyone have any experience using Gregory Snider's 1D Schrodinger/Poisson solver? I'm trying to do some simulations of a quantum well my group is studying, and I'm not sure if I'm doing something wrong or if the code is buggy or if I'm just interpreting the results incorrectly. Here's the...

I am interested in taking a measurement with a Spectrum Analyzer from an amplifier circuit I'm putting together and am interested in calculating the total power over a certain bandwidth. Is is just a matter of taking all the readings in dBm, converting to watts and then taking the RMS values...

Can anyone help explain how one can apply information say from an energy band diagram of an element/compound to its respective fermi surface / "sphere"? I understand there is a direct relationship, however, I can seem to physical interpret how one is able to say look at the energy band...

Hello! There're very thin (4-15 nm) semiconductor films (passive film) formed on stainless steel by electrochemical method. In a electrochemical cell, I applied potential on stainless steel electrode to adjust Fermi level of the semiconductor passive film. I think that band bending take place...

Hmm...some experimenting led to an interesting result. I attached a weight to a rubber band and suspended the rubber band in some hot water. The rubber band expanded. I repeated the experiment in cold water and the band shrank. An expected result, yes? Well I redid the experiment in air and I...

Hi: I am trying to show that the Mobius Band M is a bundle over S^1. It seems easy to find trivializations for all points except for the trouble point (1,0). This is what I have so far: Let R be the reals, and I<R be the unit interval [0,1]< R (i.e., [0,1] as a subspace of the...

I'm in the middle of doing an experiment where I find the heat dissipation by hysteresis through the stretching of an elastic band. I have experimentally found out how much heat is dissipated, but I was wondering if there is a way to theoretically find out the dissipated heat, most likely by...

Hi, all, I want to calculate the band structure and there is example such like that: BandLinesScale pi/a %block BandLines # These are comments 1 0.000 0.000 0.000 \Gamma # Begin at Gamma 50 2.000 0.000 0.000 X # 25 points from Gamma to X 20 2.000...

Hi, Not sure if I'm asking this in the right place, but I was wondering about the energy stored in a rubber band for a physics project I am working on. We all know that for a spring or rubber band being extended, the restoring force is given by F=-kx, and the energy stored U=0.5kx2. However...

Homework Statement What is the effective mass of the electron at the bottom of the band and at the corner of the Brillouin Zone? What is the significance of these results? Atoms lie on a square lattice of side a. Homework Equations E(kx,ky) = C{1 - cos(kxa) - cos(ky)} The Attempt...

How does the band gap not violate the principle of least energy? Surely the most favourable states are those with minimum available energy - but there is a gap!

I'm not from the chemistry major but I need to learn solid state chemistry out of the need of my research. I viewed solid state chemistry lectures online delivered by professor Donald Sadoway from MIT. Particularly on the topic of conductors, insulators, semi-conductors, I have some confusions...

Hi everyone! I wanted to ask if in your opinion is it right to say that band structure calculations (and hartree fock calculations) could live in a framework of the fermi liquid theory where quasiparticles are one-electron states (which could be or not could be the case)...

Just got a "thought experiment" question from a colleague. The question, as phrased was: If an audio signal was composed by adding all of the frequencies in the audible range, what would it sound like? I thought it was interesting, so I attempted to solve it by integral. My calculus skills...

In the band theory it is said that, in conductors, conduction bands are only half-filled. So, when Electric filed is applied, the electrons can easiliy jump into higher energy states of the same band and move freely. If the electrons a so free to move, what constitute the resistance of the...

[b]1. The problem: Suppose a rubber band obeys the equation of state: L = f (b/T), where L is length, f is tension, b is a constant, and T is temperature. For this rubber band, determine (δC[SUB]L/δL)[SUB]T, i.e. the change in the constant length heat capacity with length at constant...

hi, I have this problem where I am supposed to show, using periodic boundary conditions, that there are 2N states in an energy band in the "nearly free electron" model of solids, where N is the number of atoms. I have been looking through my course notes and my textbook, and my textbook goes...

hi , I am working on bandstructure of AlxGa1-xAs/GaAs Quantum well with 8 band k.p method , but the results for CB,LH,HH and spin orbit splitting are different from other sources, for example CB energy for Al0.25Ga0.75As/GaAs (barrier and well width=50 A) with my program is 49.83 meV whereas...

I am reading the Band Theory of solids.Now, my question is on the basic concepts: {1}When energy is given to a solid, the electrons bound to the respective atoms move from the valence band to the conduction band and hence conductivity of material increases. {2}But we know that when we give...

Homework Statement http://img121.imageshack.us/img121/2910/ssphysucks.th.jpg Stuck on 1d Homework Equations Na - Nd = p0 p0 = nie(EF-Ei)/kT kT here is 0.0259 eV n0 = (ni)2/p0 Nv = p0e(EF-EV)/kT Nc = n0e(EC-EF)/kT The Attempt at a Solution I have found: p0 =...

Please, I found this (the 4 lobe object in the center): http://www.physics.utoronto.ca/lecture-and-seminar-series/colloquium/events/tsuei.jpg But is it the same throughout the z axis, or does it vary significantly?

Hello all. I'm having trouble finding anywhere but my (unclear) lecture notes about the total number of states in a band. I'm getting a little muddled between my different models and am just wondering if the number of states in a band is equal to the number of atoms in the solid. In this case, a...

Do I understand this?-if I stretch a rubber band from a 1" length to a 2" length... If I stretch a rubber band from a 1" length to a 2" length, is it true that it was not all possible lengths between 1" and 2" sometime during the stretch? In other words, at some level, quantization enters in...

hello, i am trying to get familiar with magnetic dichroism, first question on that is, why bands of same symmetry are not allowd to cross each other and why as a consequence hybridization gaps are formed. thanks for help