Questions tagged [solid-state-physics]
Solid-state physics studies how macroscopic properties of solids (mechanical, electrical, optical, etc.) result from their microscopic structure. It usually deals with the scale where quantum properties of the particles are substantial.
3,218
questions
0
votes
0
answers
6
views
Partition function for dipolar dielectrics
How to write partition function for non-polar and polar dielectric materials. For dipolar dielectric materials we can easily write partition function. It is proportional to exp(βμEcosθ) where μ is ...
- 1
0
votes
0
answers
16
views
Why do we have overscreening?
In lecture, we discussed electron shielding as an additional influence in the interaction between electrons and ions.
My understanding of shielding is that because of coulomb force, electrons have a ...
- 1
0
votes
1
answer
19
views
Question about Drude's model of conduction
Why is it proper to assume the electronic velocity after collision is zero in Drude's model?
(Where are momentum and energy conservation?)
- 1
0
votes
0
answers
10
views
Mott dengerate semiconductor as absorber in solar cell
Does dengerate semiconductor—which met the Mott criterion—serve any purpose as an absorber for the photovoltaic effect in solar cell applications?
- 121
0
votes
1
answer
34
views
What are active deformable particles? [closed]
Could anyone please clarify to me what are "active particles", in particular "active deformable particles"?
They are mentioned in a project in Statistical Mechanics, but I have ...
- 9
0
votes
0
answers
16
views
One calculation related to condensed matter physics and berry phase [closed]
I have encountered one question about the berry phase, and I am clueless how to calculate it. I can now use the ansatz given in the problem, and then write $|\Phi(T)\rangle=e^{i\left(\varphi_{\mathrm{...
- 19
0
votes
0
answers
15
views
Barrier layer photovoltaic effect (BLPVE) and Bulk photovoltaic effect (BPVE)
Ferroelectric materials typically exhibit the bulk photovoltaic effect (BPVE). My question is that if a material taken as an absorber in a device which works on barrier layer photovoltaic effect (...
- 121
0
votes
0
answers
22
views
Interpretation of negative density of states and fourth type Van Hove singularity?
If I have the energy of a free electron gas in 3D centered at $E_0$ energy:
$$E_n(k)=E_0+\frac{\hbar^2}{2}(\frac{k_x^2}{m_x}+\frac{k_y^2}{m_y}+\frac{k_z^2}{m_z})$$
I can prove that the density of ...
3
votes
0
answers
35
views
Understanding the concept of hole in semiconductor physics [duplicate]
I've studied the Kronig–Penney model and learned about the effective mass theory and I know that at the top of the valence band the effective mass of electrons are negative, this is just an ...
- 283
0
votes
0
answers
18
views
Why do defect energy states appear only in the band-gap?
It has been shown that defects (due to doping for example) in a semiconductor cause a "tail" to appear in the density of states.
Why do these states appear in the bandgap,and how is the ...
- 1
0
votes
0
answers
39
views
Why is collector-emitter breakdown voltage (open base) lower than the collector-base breakdown voltage (open emitter)?
I need to understand why the collector base breakdown voltage is greater than collector emitter breakdown voltage. Can it be analyzed from the energy band diagram so as to remember it mnemotechnically?...
0
votes
0
answers
14
views
Williams-Landel-Ferry (WLF) and Vogel-Fulcher-Tammann (VFT) equations
I'm doing some research on polymers (vitrimers to be precise) and I have recently come across the Williams-Landel-Ferry (WLF) and Vogel-Fulcher-Tammann (VFT) equations. I am struggling to find the ...
0
votes
0
answers
64
views
Deriving BJT transistor equation
Is it possible to derive the behavior of BJT transistors using semiconductor physics?
I have seen a derivation of PN junction behavior using some assumptions which was plausible to me but I had a ...
- 834
0
votes
1
answer
17
views
Why do I need to take the number of conduction band valleys into account when calculating the Landau Level degeneracy?
I have a question regarding the degernacy of the Landau Levels. On the lecture slides it says that the spin and valley degrees of freedom need to be considered when calculating the degeneracy of ...
- 1
0
votes
1
answer
39
views
Finding solutions for the free electron model with Born-Von-Karman boundary conditions
I'm trying to solve the Schrodingers equation for the free electron model with the Born-Von-Karman boundary conditions.
I'm aware that at least a possible solution of the problems are plane waves ...
- 225
1
vote
2
answers
119
views
Why is the Lattice of a crystal required to have at least as much symmetry as its motif?
I know that a crystal structure is formed by the addition of a motif to a lattice (crystal structure = lattice + motif). I also know that an arbitrary lattice will in general exhibit certain ...
- 1,517
2
votes
1
answer
51
views
Variational method in the tight binding approach
I'm trying to read Professor David Tong's notes to understand the principles behind the tight-binding model - section 2.3.5 'Deriving the Tight-Binding Model'.
He first considers the Hamiltonian of ...
3
votes
1
answer
40
views
Is Thomas-Fermi screening the result of a Thomas-Fermi model in an external field?
On the one hand, the theory of Thomas-Fermi screening describes the response of an ideal metal (or electron gas) in the presence of an external field. In this theory, one assumes that you have a Fermi ...
- 3,968
1
vote
1
answer
29
views
Enumerating all the crystallographic directions over a half sphere in a crystal
Im taking alook at this paper [1] where there is the following statement:
CO2 was treated as a linear rigid molecule and energies were computed for 61 orientations at each center-of-mass position. ...
- 113
0
votes
1
answer
30
views
Free electron transport theory derivation
I am going through the Introduction to solid state physics
Book by Charles Kittel.
In the section regrading Free electron transport theory, i am confused by a statement "In the absence of ...
- 197
0
votes
1
answer
31
views
What mechanism causes failure in a BJT when collector current is exceeded? [closed]
Does exceeding the rated collector current of a BJT cause the device to fail because it suddenly heats up very fast? Or is there some other reason?
If the reason is heat, I'm wondering if I can exceed ...
- 127
3
votes
1
answer
174
views
Making sense of band theory for nonmetals
For the case of metals, we observed that metals often have nearest-neighbours in excess of the maximum valency (for example, 8 for Li, which has only one valence electron) and that metals display ...
- 1,034
0
votes
0
answers
29
views
Band structure of Graphene and Tight Binding
Consider the $sp^2$ hybridization of Carbon in Graphene depicted in the following picture:
When considering the LCAO TB method, one would expect conduction properties to be determined by the ...
- 101
0
votes
0
answers
34
views
Tight binding model, get dispersion relation in crystal
I know the theory of tight binding model but don't know how to apply them in the real lattice
0
votes
1
answer
74
views
Fourier transform of Hamiltonian of free particles in electromagnetic field
It is well known that the Hamiltonian of free particles in an electromagnetic field in real space is:
$$
H_R=\frac{1}{2m}\int d\mathbf{r} \Psi^\dagger (\mathbf{r}) \left(-i\hbar\nabla-e\mathbf{A(r)}\...
- 731
0
votes
1
answer
26
views
Magnetic component of electromagnetic radiation near a cooled supercunductor
What happens to the magnetic component of an electromagnetic radiation, laser for example, when interacting with a superconductor below its critical temperature? Does Meissner effect appears in such a ...
- 1
2
votes
0
answers
52
views
Is there a way to calculate the madelung constant using exponentials?
So I want to evaluate the Madelung constant for NaCl,
$$\sum_{\substack{j, k, \ell=-\infty\\\text{no}
\, j=k=\ell=0}}^{\infty} \frac{(-1)^{j+k+\ell}}{\sqrt{j^2+k^2+\ell^2}}.$$
My professor mentioned ...
- 99
1
vote
1
answer
62
views
Is degeneracy split a particular case of Hamiltonian diagonalization in 1D nearly free electron model?
In the nearly free electron model, the diagonalization of the Hamiltonian leads to the equations: $$E_0(k,h_n)A_n + \sum v_mA_{n-m}= EA_n$$ where $E_0$ is the energy of the free electron model, $h_n = ...
- 13.7k
5
votes
2
answers
101
views
How does one show that the ${\bf k}$-vector labeling a Bloch state is an arbitrary real vector?
I'm frustrated that I can't understand something that must be simple and fundamental. I'd appreciate any answer to the question, but also any clarifications of how my presentation of the theorem/proof,...
- 558
0
votes
0
answers
28
views
Sign of Wave Number and Angular Frequency
In chapter 9, page 78, of The Oxford Solid State Physics Basics by Steven Simon, the author claims an ansatz given by $$e^{iwt-ikna}$$ as a solution of 1D monatomic chain of atoms connected by ...
- 73
0
votes
0
answers
30
views
Experiment describing superconductivity discovery [duplicate]
We study in Ohm's law that current $I$ is directly proportional to voltage difference $V$ between two points, where resistance $R$ is the proportionality constant.
In 1911, if K. Onnes measured ...
- 119
0
votes
0
answers
51
views
Chemical potential $\mu$ controls filling?
If total magnetization of a spin 1/2 system is zero, does it mean that system is at half filling? or chemical potential $\mu=0$? I was trying to show that chemical potential controls filling by taking ...
- 427
2
votes
3
answers
211
views
What happens inside a conductor when the current faces resistance?
According to my book resistance depends on the the number of collisions free electrons suffer in any conducting device. Now insulators have no free electrons so how do they have high resistance like ...
- 39
1
vote
1
answer
56
views
Number of Possible Primitive Vectors and Primitive cells in a Bravais Lattice
According to my Book Solid State Physics by Ashcroft and Mermin, given a 3-dimensional Bravais lattice, there are infinite sets of 3 primitive vectors that we can come up with that will span the ...
- 73
1
vote
1
answer
29
views
Electron localization in crystal
I tried to use indetermination principle to explain why, electrons that are strongly bounded to the nucleus, are more localized. Unfortunately, the result that I've obtained says the exact opposite. ...
- 1,680
1
vote
1
answer
49
views
One-dimensional reciprocal lattice
I've seen that, a possible defining condition for the reciprocal lattice is:
$\vec R_s \cdot \vec G=2 \pi l$, where, $R_s= n_1 \vec a_1+n_2 \vec a_2+n_3 \vec a_3$ is the direct lattice, $\vec G$ is ...
- 1,680
1
vote
0
answers
65
views
Meaning of spectral function of spin Green's function?
Since spins are neither bosons nor fermions, spin Green functions can be defined using either a commutator ($\eta=-1$) or an anticommutator ($\eta=1$), e.g., $$G_{ij,\eta}(t,t')=-i\theta(t-t')\langle[...
- 3,352
1
vote
1
answer
70
views
How can the total momentum of a crystal be conserved?
In general, the total momentum of a system is conserved. Nevertheless, the momentum of a single electron or phonon is not conserved in a crystal. In fact, for an electron there are two types of ...
- 409
1
vote
1
answer
40
views
Momentum conservation in phonon-photon scattering event
I am following a discussion from Kittel´s Introduction to Solid State Physics in the subchapter ‚phonon momentum‘:
We have two different conservation laws of momentum in a crystal:
Total momentum is ...
- 409
3
votes
0
answers
45
views
Zero frequency limit of Hall conductivity not quantized?
The transverse conductivity $\sigma_{xy}$ at zero frequency is quantized when the chemical potential $\mu$ is within the gap for a topological system, such as quantum Hall effect and Haldane model. ...
- 3,352
4
votes
0
answers
80
views
Does Hall conductivity change sign with chemical potential?
The transverse conductivity $\sigma_{xy}$ at zero frequency is quantized when the chemical potential $\mu$ is within the gap for a topological system. A typical plot of $\sigma_{xy}(\mu)$ is like the ...
- 3,352
1
vote
2
answers
72
views
What's actually happening on the level of individual particles when an atom in a solid is vibrating?
For context, I'm trying to understand what happens to the kinetic energy of an electron in semiconductor after it absorbs a photon with more energy than the bandgap. My QM professor said it gets ...
1
vote
0
answers
32
views
What happens to the kinetic energy an electron gains from absorbing a photon with more energy than the bandgap?
For context, I'm taking a course on quantum mechanics geared towards electrical engineering majors (so basically the standard curriculum, but with additional focus on EE applications, particularly in ...
2
votes
0
answers
78
views
How does photon reflection work quantum mechanically? [duplicate]
When a single photon strikes a mirror, it is reflected back such that the incident angle= the reflected angle. When the photon interacts with the surface lattice of the mirror, what exactly is ...
- 595
1
vote
0
answers
60
views
Master thesis topics [closed]
I'm studying a Master degree in condensed matter physics but I've been always interested by theoretical physics, especially QFT and now I need to do a master thesis for graduating and I'm looking for ...
6
votes
1
answer
219
views
Wave equation for phonons
Question: What is the relativistic (quantum) wave equation that governs that motion of phonons?
My Attempt(s): The phonon Hamiltonian is given by, $$\mathscr{H} = \dfrac{1}{2}\sum_n \left(p_n^2 + \...
- 658
1
vote
0
answers
28
views
Semiconductor Band Gap
I have a conceptual question.
Say at room temperature, electron has thermal energy of the order of 25 milli eV. Consider Germanium having band gap of 0.7 eV, so the corresponding temperature will be ...
- 119
0
votes
0
answers
21
views
What is the mass absorption coefficient and how it is determined?
I would like to know what is mass absorption coefficient in the field of x-ray spectroscopy means and how can we determine this value experimentally (or by simulation) and also why for some materials ...
1
vote
0
answers
27
views
The DOS effective mass
If we consider the spin-orbit coupling in semiconductors, it is known that the degeneracy of the valance band is lifted up and we got 2 sub-bands the light hole and the heavy hole that are still ...
1
vote
0
answers
38
views
What is a 'satellite' in solid state physics?
During a course, my professor talked about satellites. He defined them as an excitation which results in an electron-hole pair, in a system of interacting electrons. So that the energy of the ...
- 43