Stack Exchange Network

Stack Exchange network consists of 174 Q&A communities including Stack Overflow, the largest, most trusted online community for developers to learn, share their knowledge, and build their careers.

Visit Stack Exchange

Questions tagged [electronic-band-theory]

The tag has no usage guidance.

2
votes
0answers
32 views

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 ...
1
vote
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
votes
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
votes
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 ...
1
vote
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
vote
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
votes
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
votes
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
votes
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
vote
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
votes
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
votes
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
votes
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
votes
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
vote
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
votes
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
votes
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
votes
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 ...
1
vote
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
votes
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
votes
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
votes
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
votes
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
votes
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 ...
1
vote
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
votes
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
votes
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
votes
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 $qV$? $\hspace{50px}$
0
votes
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 ...
0
votes
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'...
0
votes
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
votes
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
votes
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?
1
vote
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
votes
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
votes
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
votes
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 ...
1
vote
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
votes
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 ...
0
votes
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
votes
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 ...
1
vote
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 ...