Questions tagged [electronic-band-theory]
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0answers
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Energy bands. Bonding and antibonding orbitals
In tight-binding wikipedia article it is said that bonding and anti-bonding orbitals correspond to different $k$-values in a single energy band. At the same time in Cordona Fundamentals of ...
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4answers
90 views
Can we / should we use the Pauli principle to explain band structure?
Checking the wikipedia article on band structure, I got caught in major doubts...
They try to give an intuitive explanation of the band structure relying heavily on Pauli Exclusion Principle:
if a ...
0
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1answer
31 views
Electronic band structure of proteins
Proteins are a class of macromolecules. What range of electronic band structure do These have? Are These more like semiconductors? Or like insulators? How high is the typical Fermi Level for Proteins?
...
0
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1answer
26 views
Is there a simple rule connecting all indirect semiconductors band gaps to their electron-hole pair generation average energy?
The band gap of Diamond, Silicon and Germanium is 5.5, 1.12, 0.66 eV while the average energy to produce an electron-hole pair for
the same semiconductor is namely 13, 3.6 and 2.9 eV. This ratios are ...
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3answers
69 views
Electronic band structure
I want to know why the bands like valence or conduction splits up into two parts as shown in this diagram. why the energy gaps exist with in these bands? As you can see in this diagram that their is ...
1
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1answer
24 views
Why does first photonic band go to zero at the centre of the Brillouin zone?
I have been plotting photonic band diagrams of various geometries recently and I identify if it is correct by looking if it goes to zero at the Brillouin zone centre, $\Gamma$. I realised early on ...
-2
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1answer
103 views
Putting high symmetry points labels to a band structure plot [closed]
So far I've got this plot using Quantum Espresso. I want to put gamma, X, L, etc labels to the k-path.
Quantum Espresso's ouput states the following:
...
0
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1answer
31 views
At what temperature is the band gap value when obtained from Arrhenius plot?
Using the equation
$$\ln{R}=\ln{R_0} + \frac{E_G}{2k_B T}$$
we can obtain the band gap value $E_G$ by measuring a sample's resistance $R$ with changing temperature $T$ and using the parameters of the ...
0
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1answer
32 views
What is the binding energy between conduction band and valence band of metals and insulators?
As far as my understanding of solid state physics goes, I can't see a clear connection between binding energy and band gap. But our teacher asked us the question as an assignment but i really can't ...
1
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1answer
77 views
What does the concept of “free electron” mean in the context of band theory?
Often when conductivity is explained through band theory, the term "free" tends to crop up. As an example, I often come across descriptions of the valence band as a highest filled set of states ...
0
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1answer
45 views
Energy band gap
I am studying from the Aschroft & Mermim. In the chapter 8 they prove the Bloch theorem and introduce the concept of band.
they say that k is a quantum number that charactrize the eigenfunction ...
11
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6answers
213 views
Can amorphous solids have energy bands?
One can understand the formation of energy bands from the Kronig-Penny model which assumes a periodic potential. But I heard that even if the potential is aperiodic, for example in amorphous ...
0
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1answer
40 views
Is the band theory valid for an electron with energy greater than the potential?
Consider Kroenig Penney model. Here there is a derivation that uses the following potential:
One of the assumption is that the energy of the electron is $E<U_0$. Under this assumption (and others) ...
2
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1answer
50 views
Why does the 2D hexagonal lattice have a different tight binding band structure than Graphene?
Here you can find band structures for various tight binding models. I was wondering, why the 2-D hexagonal lattice has a different band structure than Graphene, even though they have the same lattice.
3
votes
1answer
118 views
How to calculate conductivity / electron mobility from theory?
Is there a way to make quantitative statements about the conductivity of materials with band theory?
If not I should still be able to get information about the conductivity from Green-Kubo relations ...
1
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1answer
60 views
How can I calculate the chemical potential and the effective masses in an intrinsic semiconductor?
I want to calculate the chemical potential and the effective masses of the germanium charge carriers considering that the relaxation time is the same for the two carriers: electrons and holes. ...
2
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0answers
29 views
How can I draw the energy bands for the first and second zones of Brillouin? Is it conductor or insulator?
I want to draw the energy ($E$) diagrams for a simple cubic cell of parameter $a$, where each atom provides two electrons for the almost free electron levels for planes [100], [110] and [111].
I ...
2
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2answers
75 views
Orbitals without overlaps in band structures of solids
We know every band in the band structure of solids is the result of overlaps of an orbital type. My question is that when there is not any overlap between a type of orbitals(which may be the lowerest ...
0
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1answer
49 views
Is diamond able to conduct electricity given 5.5 eV of energy? How do we then identify insulators and semiconductors?
I have learnt that the band gap for diamond, an insulator, is $5.5\:\rm eV$. Does this mean that diamond is able to conduct electricity if we give it this immense amount of energy (let's assume we do ...
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3answers
216 views
Conduction and Valence band
What is the difference between a conduction and valence band ? How an electron will behave different in conduction and valence bands ? When an electron leaves an atom the atom becomes ion. Does it ...
0
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1answer
54 views
Can someone give a simple mathematical explanation of the tight binding method?
I'm trying to understand the tight binding method but I'm struggling with a lot of the mathematical formalism. A lot of the mathematical formalism I read jumps into explaining it a few too many steps ...
2
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0answers
31 views
What is it about metal elements that means their conduction and valence bands overlap, as opposed to non-metal elements where there is no overlap?
I can't see why metals have overlapping bands and a higher Fermi level compared to Non-metals where there is no overlap and the Fermi level is not in the conduction band.
0
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1answer
41 views
Mental contradiction: Valence electrons do not move at the non-zero wavevector?
I have a mental contradiction. Let's consider the following band structure with the Fermi energy somewhere inside the gap:
where $\Gamma$ point represents the zero value of the wavevector $|\vec{k}|$....
2
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2answers
67 views
What is the significance of the time $\hbar/E_F$ where $E_F$ is the Fermi energy?
For free electrons in a metal, the Fermi energy $E_F$ (defined as the highest filled energy level at $T=0$). It represents a characteristic energy scale of the system as well as the energy of the ...
2
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0answers
30 views
Rashba effect in 2DEG (how there is non zero electric field)
In the right column of page 20 in this paper, spins in few-electron quantum dots, the paper says "It is at first sight surprising that there
is a net spin-orbit interaction: since the state is bound
...
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0answers
22 views
The Hermicity of k.p Hamiltonian with operator ordering?
I am trying to use the k.p method to study quantum well band structure. One example Hamiltonian look like this [J. Appl. Phys., 116, 033709(2014)]
[]1
where
${{\hat k}_ \pm } = {{\hat k}_x} \pm i{{\...
0
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2answers
80 views
Is Fermi Level a property of the material?
I have gotten myself confused about the band structure explanation of semi-conductors vs insulators. The Wikipedia picture
and the explanation surrounding it seem to suggest that Fermi Level is a ...
5
votes
1answer
167 views
Is topological surface state always tangential to bulk bands?
Think of a topologically nontrivial $D$-dimensional system. Its bulk bands form a $D+1$-dimensional manifold ($+1$ from energy). Its surface/edge bands form a $D$-dimensional one. Is the latter always ...
5
votes
1answer
136 views
What happens when we add free electrons to an insulator?
I'm trying to understand why an insulator doesn't conduct electricity. If I understand correctly, the energies of electrons of an insulator are bound tightly to the nucleus, so there are no free ...
0
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1answer
39 views
Variational calculus and KKR method for band structure calculation
I’ve been studying the KKR method from the original Kohn and Kostoker’s paper (https://journals.aps.org/pr/abstract/10.1103/PhysRev.94.1111).
On the text, they use variational calculus for dealing ...
3
votes
1answer
115 views
free electron approximation verses tight binding approximation
What is the relation between electronic band structure that is calculated by using free electron approximation (FEA) and tight binding approximation (TBA)?
My understanding:
In FEA, it seems we ...
1
vote
1answer
36 views
Can the graphene's conductivity be explained using only orbitals?
I am trying to find a 'easier' or more 'intuitive' way to calculate the conductivity of graphene. I want do this by using atomic or molecular orbitals. Anyone have a clue about how this can be done? ...
0
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0answers
80 views
Fermi Dirac probability relative to electrons and holes
I'm having a hard time to understand the following sketch:
especially in case of the second diagramm. What does E against f(E) mean? How do I interpret this? The probability f(E) of an electron is ...
1
vote
1answer
44 views
band gap energy (discrete or continous?)
What does the band gap energy mean explicitly? Is it a single, discrete energy or is it a energy region? Sketches always show a "gap" between the conduction and the valence band so I assume there are ...
1
vote
1answer
83 views
Why is there a difference between Fermi levels in metals and metal-oxide semiconductors (MOS)?
Why are Fermi levels in metals lower than the Fermi level of $\text{p}$-substrates in metal-oxide semiconductors (MOS)? Specifically, why is there a difference of $qV$?
$\hspace{50px}$
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2answers
57 views
Energy of electrons?
Whats meant by energy of electrons in different orbits of atoms. Does this means that the electrons at higher evergy levels have more kinetic energy as compared to the electrons at lower energy level ...
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0answers
26 views
Why do we need to know “two-bands” Hall coefficient and magnetoresistance?
I know only partially filled bands result in current density, and I think there must be not only 2 partially filled bands, but "several" partially filled bands. For each partially filled band, its Ohm'...
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1answer
27 views
Acceptors with very high energy level in semiconductor
I have gallium arsenide (energy gap of 1.4 eV) doped with silicon in concentration of $10^{14} cm^{-3}$ and energy level very close to the conduction band so it's act like a donor. Now we put in also ...
0
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0answers
23 views
Band theory- Is the conducting band the last orbital with a gap between the two bands?
What I understand is in each atom there are conducting and valence bands
and the valence band, the minimum level for electrons (is the orbital before the last)
Is the conducting band the last ...
0
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0answers
80 views
Band structure and Density of states (DOS)
Can someone explain how these two plots are related?
How are the peaks in the right are associated with the left figure?
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0answers
34 views
Is band theory applicable only for valence electrons
Is band theory applicable only for the valence energy levels of a metal?
When metal atoms come together the valence electrons occupy a band of energy levels. But does the energy of the inner ...
0
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2answers
158 views
Fermi-Dirac function electron and hole concentration
I have a question regarding the Fermi-Dirac function. I would like to confirm that my basic understanding is correct.
Is any space under the curve in the CB and VB describe the probability of finding ...
0
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0answers
22 views
Obtaining low energy effective model of Bernal stacking bilayer graphene
I am now reading some articles about the electronic properties on Bernal stacking bilayer graphene. (https://arxiv.org/abs/1205.6953).
In the section II-C-1, the general procedure of obtaining the ...
0
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1answer
102 views
Pseudopotential in VASP
I am a beginner in learning VASP (Vienna Ab-initio Simulation Package) and quite interested in the PAW (projector augmented wave) method implemented in VASP. As far as I knew, PAW is an all-electron ...
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0answers
60 views
PT-symmetry in Energy Band of Crystals
According to this source, it is proved that, in absence of spin-orbit coupling, spatial inversion symmetry (as a part of point-group symmetry which operates as $\hat{S}\psi(\vec{r})=\psi(-\vec{r})$) ...
2
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0answers
158 views
What's the transition from “metal” to “electron-degenerate matter” look like?
Question: Say that we had metallic water and compressed it until it qualitatively resembled the state of matter in a white dwarf: what would that transition look like?
Background (revised to be ...
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0answers
80 views
How do you calculate effective mass exactly?
I know about the equation m*/me=hbar^2[(d2E(K)/dK2)]^-1. You need to get the second derivative of the E-K diagram at the point of interest. For electron effective mass, that's the lowest point in the ...
0
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1answer
49 views
Conventional explanation of basic Semiconductor & Diode behavior unconvincing
I have seen this and this and a few other. Throughout the web and notes I find the explanation of the workings of a simple diode sort of unconvincing and I am depressed by the fact that I am not able ...
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1answer
56 views
The band gap in many-body theory
I would like some help in understanding the definition of the band gap in many-body theory. I have seen several books state that the fundamental band gap is given by
\begin{align*}
E_{\text{gap}} = \...
3
votes
1answer
530 views
How diffusion and drift current in a PN junction get equal?
Let's consider a PN junction which is at zero biased voltage. Once the junction is formed charges are diffused across the junction and form the depletion region and stops further diffusion. So no ...
