Questions tagged [electronic-band-theory]
Use this tag to ask about band-structure formation in solids, or about how electrons and holes behave inside them.
606
questions
0
votes
1
answer
31
views
Why no acceptor energy level in pure semiconductor?
Why there is no acceptor energy level in pure semiconductor? (assume some holes are formed due to heat), While the holes created here to effectively conduct electricity , bonded electrons must ...
5
votes
2
answers
406
views
What does it mean if the Fermi level crosses into the valence band? How about into the conduction band?
I've been working on this material to get more accustomed to Quantum Espresso, and I've gone on and performed calculations to get their band structures. Here are the band structures that I got for two ...
- 51
2
votes
1
answer
42
views
Questions regarding physical electronics [closed]
I ran into some questions while studying physical electronics.
My textbook/lecture note says "An electric field applied to a semiconductor will produce a force on electrons and holes so that ...
- 439
0
votes
0
answers
13
views
Quantum well in confining structure
I was studying the confining of electrons in a composite crystal. I don't understand how the fact that the band gaps of the two materials are different translates immediately to the statement that ...
1
vote
0
answers
31
views
Numerical calculation of berry curvature of Haldane model
I'm currently trying to simulate the Haldane model of graphene and am looking into the calculation of Berry curvature of the finite lattice. I'm using a tight-binding model of graphene with nearest-...
3
votes
4
answers
84
views
Doubt about interpreting Fermi level in semiconductors
Before I say anything, I know there's already a bunch of questions about the Fermi level in semiconductors on this website but I don't think my doubt in particular has been addressed before.
From what ...
0
votes
0
answers
18
views
Interpretation of Floquet Band Structure in Multi-band Models
Computing band structures inside Floquet formalism has become quite common, see e.g. [1]. While I think to fully understand it from a mathematical point of view, I'm lacking some physical ...
- 85
1
vote
1
answer
36
views
Relation between Fermi surface and Fermi velocity
Is there a direct relation between the Fermi velocity and the Fermi surface? Can one reconstruct the Fermi surface if the full angular distribution of the Fermi velocity is known?
- 185
0
votes
0
answers
9
views
Reference for empirical Tight-binding Hamiltonian of spds* vs sps* (ZB)
Is there a clear reference article/note for the 20X20 Hamiltonian matrix of the spds* Zinc Blende system similar to the sps* reference in
[1] Table (A) of Vogl P, Hjalmarson HP, Dow JD. A Semi-...
1
vote
0
answers
28
views
Electronic bands and Aufbau principle
In atomic theory there is Aufbau principle stating (Wikipedia)
The rule states that for a given electron configuration, the lowest energy term is the one with the greatest value of spin multiplicity. ...
- 806
0
votes
0
answers
17
views
Formation of valence and conduction bands from atomic orbitals
In the wiki article on the electronic band structure illustrates on how the valence and conduction bands of group 4 semiconductors like diamond emerge from the 2s and 2p orbitals of the C atoms.
...
- 1
1
vote
0
answers
38
views
Why is the time evolution of occupied and unoccupied levels in a band under the influence of applied fields the same?
I am studying the semiclassical model for solid state physics as described in Chapter 12 of Ashcroft & Mermin. While I am familiar with the concept of holes, a formal argument is made in this ...
4
votes
0
answers
47
views
Are there charge fluctuations in band insulators?
Consider a one-dimensional non-interacting Hubbard Hamiltonian:
$$
H=-t\sum_{\langle i, j \rangle}\sum_{\sigma=\uparrow,\downarrow} \left(c_{i,\sigma}^\dagger c_{j,\sigma} +\mathrm{h.c.} \right)
$$
...
- 990
0
votes
0
answers
22
views
Relationship between band structure and band diagram?
I'm having a hard time making a connection between band structure and band diagram. I know in simple terms, band structure is a representation of the allowed electronic energy levels in k-space, and ...
- 280
0
votes
1
answer
35
views
Valence and conduction band definition in metals
In the textbook examples, the band character (VB and CB) of semiconductors is explained by their location above (CB) or below (VB) the Fermi level. In metals however, the valence and conduction bands ...
- 185
0
votes
0
answers
26
views
Transmission coefficients for periodic barriers and energy bands
I have been looking at transmission coefficient vs energy graphs (source:reference) and how it relates to when we increase the number of periodic barriers.
The resonant energies(where transmission co-...
- 15
0
votes
0
answers
21
views
Are electrons quantum confined in two-dimensional semiconductor materials?
In the case of superlattice devices, such as HEMT, the carriers are confined to a two-dimensional quantum well and form what we call 2DEG. Hence, when calculating the carrier density, we need to ...
0
votes
1
answer
82
views
Can an electron in a given band have a well-defined position?
In a book I am using (Quantum Theory of the Optical and Electronic Properties of Semiconductors, chapter on Quantum Dots), they define separate position space creation operators for an electron and ...
- 1,287
0
votes
0
answers
24
views
How does reflection of light work on an atomic scale? [duplicate]
Let's say white light is incident on an orange. It absorbs wavelengths via the excitation of the atoms within the molecule that gives it pigment, but how do these molecules reflect that orange ...
- 3
0
votes
1
answer
34
views
Having trouble understanding light absorption versus reflection
Do the atoms within a material absorb the photons and re-emit them in the direction they came back from (similar to atomic emission spectra, but slightly different because this involves hybridization ...
- 3
0
votes
0
answers
31
views
How do lattice sites relate to an electron's momentum
I'm trying to wrap my head around band transport of electrons in a semiconductor, and am lacking intuition as to why an electron moving from one site to another site in reciprocal space (and therefore ...
2
votes
1
answer
39
views
How to unfold electronic bands? How do the reduced/extended schemes work? Confusion regarding the quasi-momentum
One of the simplest models for electronic band structures is a tight binding model on a one dimensional chain with spacing $a$, one atom per cell and interactions only for nearest neighbours. This ...
- 348
0
votes
0
answers
8
views
What is the effect of carrier concentration on electron scattering?
What effect does doping (or adjusting the chemical potential) have on the electron scattering rate in semiconductor materials such as Si, if the rigid band model is assumed?
- 121
3
votes
1
answer
122
views
Where do Cooper pairs fit in the superconducting density of states?
This is a very common diagram of the superconducting density of states. In a normal metal, the Fermi energy lies somewhere in the conduction band and there are unoccupied states above it in the same ...
- 1,097
4
votes
1
answer
209
views
Filled Band cannot generate current
In solid-state physics at $T=0 K$ considering the semi-classical approximation for electrons, I understand physically that if a band is completely filled, the electrons can't move and there is no ...
- 197
0
votes
0
answers
86
views
Where does Tauc's relation come from? Why is the method valid?
$$ (\alpha h \nu)^{1/r}=A(h\nu - E_g) $$
(1/r represents the nature of transition)
We were replicating an experiment from a paper in our physics lab, wherein we used the above equation and considered ...
- 49
0
votes
1
answer
47
views
How to visualise atomic triangle model from the Hamiltonian?
I am a complete beginner in consented matter theory and have been struggling to understand how some of the Hamiltonians are constructed.
I am looking at a simple example given in this book, where ...
- 181
0
votes
0
answers
35
views
Understanding $k$-axis of band structure
So right now im reading about TMDC's and there was this picture
And I dont understand the x axis. There it only says k vector. But what is it exactly ? Is it real $\vec{k}$ or $|\vec{k}|$ or $k_y$ or ...
- 165
2
votes
2
answers
60
views
Can the conduction band get completely filled?
I have just started studying basic solid state physics and I got to know that filled or empty bands do not conduct. Is this only the case for valence band or also conduction band.
Is there any case ...
- 21
2
votes
2
answers
373
views
Can electrons have energies between valence and conduction bands?
When looking at pictures of direct band gaps from a crystal lettice I wondered if it really is impossible that electrons, even if its only for a short time, occupy the Energies between the band gaps ? ...
- 165
2
votes
2
answers
48
views
How many $\rm eV$ near Fermi level are involved to the conduction of carriers? For metal and degernerated semiconductors?
How many $\rm eV$ near Fermi level are involved to the conduction of carriers? For metal and degernerated semiconductors? Someone say about ± 5 eV, but I cannot find any references to support.
- 31
3
votes
1
answer
95
views
Is there anyway to break the cubic harmonics in condensed matter
Since I started doing the calculation of condensed matters, the two $e_g $ orbitals or three $t_{2g }$ orbitals are assumed equivalent and I have never doubted this. From most books, this is also ...
- 31
8
votes
0
answers
96
views
How does one measure effective mass in a multivalley semiconductor?
I understand the answer given in this question. It explains how we can measure the effective mass in a semiconductor.
However, I wonder what happens in the case of a multivalley semiconductor. Namely, ...
- 1,641
0
votes
0
answers
28
views
How to calculate eigenfunctions for the upper and the lower band at the band edge?
I am trying to calculate two eigen functions of upper and lower band at the band edge $\frac{g}{2}$ for brillouin zone extending from $\frac{-g}{2}$ to $\frac{g}{2}$ for the eigen matrix given in ...
- 15
0
votes
1
answer
51
views
Will doping always increase charge carrier concentration?
Consider the effect of n-type and p-type doping on the band structure of a semiconductor:
Image taken from here.
The diagram shows that, for n-type doping, a number of discrete states will be ...
- 129
0
votes
1
answer
95
views
What is the allowed $k$ values in nearly free electron model?
One explanation on bandgap formation uses nearly free electron theory and Bragg reflection. The diagram used for the explanation appears:
taken from here.
I also learnt that in free electron theory, ...
- 129
0
votes
0
answers
42
views
Reflection of radiation in atoms
I want to ask how does an atom reflect an incident radiation shown onto itself?
I understand that when radiation is incident on an atom, the electrons can be excited to higher energy levels shells.
...
- 11
1
vote
0
answers
16
views
Calculating Electron Relaxation time in Nanostructures
Is there a method to calculate the electron relaxation time in nano-structures?
It would be nice to avoid methods such as DFT since the number of atoms is high and I do not have much computational ...
- 121
1
vote
0
answers
35
views
Band structure of Group-IV crystals
Talking specifically about the $sp^3$ hybridized crystals, it can be seen that all the group-IV elements from carbon to germanium sport a band gap in the bulk of their crystals, but Sn and Pb. Also we ...
- 1,338
1
vote
1
answer
46
views
Which coefficients in the central equation need to be retained for approximate solution at (or near) the zone boundary?
To obtain the band gaps near the zone boundaries from the central equation
$$\left(\frac{\hbar^2k^2}{2m}-\varepsilon\right)c_{k}+\sum_G U_G c_{k-G}=0,
$$ where $U_G$ are the Fourier coefficients of ...
- 9,073
1
vote
0
answers
50
views
Why Energy bands in a p-n junction bend counter-intuitively
Question :
How Conduction Band gets raised in energy when under a positive potential
I was trying to understand band bending with a simple model. Here, I am first considering a p-n junction that has ...
- 1,908
0
votes
0
answers
16
views
What does the toy model Hamiltonian for 3D weyl seminmetal mean?
I have been going through this Wannier tools tutorial for observation of weyl nodes in basic toy model Hamiltionan. It represents the toy model Hamiltonian as:
$$H = A(k_x\sigma_x+k_y\sigma_y)+[M_0-...
- 153
0
votes
1
answer
54
views
Does crystalline silicon have a higher (~3.0 eV) band gap than amorphous Si (~1.75 eV)? Or lower (~1.12 eV)? [closed]
Some sites claim that crystalline silicon has a band gap of approximately $1$ to $1.2$ or so electron volts, and others say it is about $3$ to $3.4$ eV....
Amorphous silicon is usually described as ...
- 3,443
0
votes
0
answers
53
views
Electrons with zero velocity but non-zero wave vector in the conduction band - how does this make sense?
In an indirect band gap the conduction band can have a minimum point somewhere near the edge of the Brillouin zone. At this minimum point the group velocity of the electrons will of course be 0 since ...
- 1,097
1
vote
1
answer
224
views
What is the physical significance of reduced zone scheme?
Different energy bands can be drawn in different zones in $k$-space is called Extended-Zone-Scheme, whereas if the different bands are drawn in first Brillouin zone, then its called Reduced Zone ...
- 456
1
vote
0
answers
54
views
What are s-bands and d-bands in band structures?
Given a band structure diagrams I can understand whether there are band gaps and what the bands are but what are s-bands and d-bands and how do I tell them apart in these diagrams?
Example:
I ...
1
vote
0
answers
18
views
How to compare effective masses in band structures?
As far as I know the effective mass in Solid State Physics is determined by inverse of the slope of dispersion relations (in band structure diagrams).
\begin{equation}
m^*=\frac{\hbar}{\frac{d^2\...
0
votes
2
answers
112
views
The difference between free electron model and nearly free electron model
In Kittel`s book, it says
The band structure of a crystal can often be explained by the nearly free electron model for which the band electrons are treated as perturbed only
weakly by the periodic ...
- 1
0
votes
0
answers
33
views
Comparing description of spontaneous absorption and description of stimulated emission
I am currently studying Diode Lasers and Photonic Integrated Circuits, Second Edition, by Larry A. Coldren, Scott W. Corzine, Milan L. Masanovic. Chapter 1.3 SPONTANEOUS AND STIMULATED TRANSITIONS: ...
- 691
0
votes
0
answers
43
views
Depletion width of Schottky diode
I'm trying to find the resistance of a Schottky (metal-semiconductor) diode where the semiconductor is N-doped. On the surface this seemed simple, I just had to find the depletion width $w$ and the ...
- 167