Tagged Questions
3
votes
1answer
115 views
Change of basis in non-linear Schrodinger equation
At the mean-field level, the dynamics of a polariton condensate can be described by a type of nonlinear Schrodinger equation (Gross-Pitaevskii-type), for a classical (complex-number) wavefunction ...
1
vote
1answer
54 views
What is paramagnetic current-current correlation?
I know what paramagnetism is. But first I want to know about the paramagnetic current and then the above-mentioned correlation?
Actually, I am working on a paper on superconductivity where I have ...
3
votes
0answers
99 views
Quantum Electrodynamics
I was wondering if anyone could give a simple explanation of how light interacts with matter. From what I have read in QED, electrons will repel each other because of their ability to emit and ...
4
votes
2answers
194 views
What prevents bosons from occupying the same location?
The Pauli exclusion principle states that no two fermions can share identical quantum states. Bosons, one the other hand, face no such prohibition. This allows multiple bosons to essentially occupy ...
0
votes
0answers
94 views
Wave function ansatz for disclinated graphene with spin
I am currently investigating spin dynamics in disclinated graphene. More information about my approach can be found in my other post. I would like to know if my approach is somewhat correct to find ...
1
vote
2answers
98 views
Eigenfunctions in periodic potential
For Hamiltonian $\operatorname H$ and lattice translation operator $\operatorname T$, if
$$\operatorname H\psi=E\psi, \qquad \operatorname T\psi=e^{ik\cdot R}\psi,$$
and
$$\operatorname ...
3
votes
1answer
208 views
Does a quantum phase transition have latent heat?
As the title says, I am thinking about the question that whether a quantum phase transition has latent heat. If so, at 0 temperature, we can drive the system by some parameter from disorder phase to ...
2
votes
2answers
351 views
What is the difference between a photon and a phonon?
More specifically, how does a wave-particle duality differ from a quasiparticle/collective excitation?
What makes a photon a gauge boson and a phonon a Nambu–Goldstone boson?
7
votes
1answer
207 views
Simulating the evolution of a wavepacket through a crystal lattice
I am interested simulating the evolution of an electronic wave packet through a crystal lattice which does not exhibit perfect translational symmetry. Specifically, in the Hamiltonian below, the ...
2
votes
0answers
76 views
What is Z3 exciton?
I am searching and studying excitons and I confronted with a term named Z3 exciton. What is it? And what is its difference with, for instance Z1 or Z2 exciton?
0
votes
1answer
85 views
Characteristics of bloch electron in a priodic potential
Effective mass of a Bloch electron in a periodic potential is negative why ?
4
votes
0answers
41 views
Order of magnetic phase transitions
Is there any phase transition occur in paramagnetism to diamagnetism transitions state. What should be the order and how will I calculate the order?
0
votes
0answers
111 views
Phase diagram problem for ternary system
For a ternary system, three composites are present.
Temperature is also a variable.
Assuming that pressure is held constant, what is the minimum number of phases that may be present in a ternary ...
8
votes
3answers
329 views
Derivation of the “Bethe sum rule”
I am trying to work out the steps of the proof of the expression: $$\sum_n (\mathcal{E_n}-\mathcal{E_s})|\langle n|e^{i\mathbf{q}\cdot\mathbf{r}}|s \rangle|^2 = \frac{\hbar^2q^2}{2m}$$ from Eq. (5.48) ...
1
vote
1answer
180 views
What is different between resolvent and green function
I bumped into a book, where Resolvent $R^{\pm}(E)$ is defined as
$e^{\mp iHt/\hbar}=\pm\frac{i}{2\pi}\int_{-\infty}^{\infty}dER^{\pm}(E)e^{\mp iEt/\hbar}$
and
$R^{\pm}(E)=\frac{1}{\pm ...
0
votes
1answer
141 views
Why do the drift and diffusion components cancel for each type of carrier if EHP generation plays such big role in p-n-junctions?
I have always argued to myself that drift and diffusion components of the current though a p-n-junction cancel for each type of carrier because any electron diffusing from n into p will sooner or ...
2
votes
2answers
231 views
How robust is Kramers degeneracy in real material?
Kramers theorem rely on odd total number of electrons. In reality, total number of electrons is about 10^23. Can those electrons be so smart to count the total number precisely and decide to form ...
1
vote
1answer
101 views
What is crystal field anisotropy or effect ? It forces the magnetic moment to point in particular local direction..
Can you give a basic explanation of what is crystal field anisotropy ?
What is the reason to arise ?
In spin ice it forces the dipoles to point in the local 111 direction.
For partially filled rare ...
1
vote
1answer
83 views
Where can I find hamiltonians + lagrangians?
Where would you say I can start learning about Hamiltonians, Lagrangians ... Jacobians? and the like?
I was trying to read Ibach and Luth - Solid State Physics, and suddenly
(suddenly a Hamiltonian ...
3
votes
0answers
64 views
Topological entanglement entropy only defined for a system in the ground state?
What happens to the topological entanglement entropy of a system, when it is driven out of its groundstate by increasing the temperature?
1
vote
1answer
361 views
Topological phase
Can anybody tell me, if generically any system, which is solely described by a topological field theory, resides in a topological phase? I cant find any clear notion of topological phase. Only ...
3
votes
1answer
124 views
How are quantum potential wells fabricated?
Potential wells, such as infinite and finite potential well, have been the standard examples in quantum mechanics textbooks for tens of years. They started being only theoretical toy models but as ...
3
votes
2answers
231 views
What are the applications of delta function potentials?
Are there real applications for using delta function potentials in quantum mechanics (other than using it as an exactly solvable toy model in introductory undergraduate quantum mechanics textbooks) ?
...
4
votes
1answer
503 views
Tight Binding Model in Graphene
I'm following a calculation done by a guy who's done it a bit different than what I've done before (used nearest neighbour vectors and a DFT instead of what I will show below), I'm not quite sure how ...
5
votes
2answers
579 views
Basic Question - Green's Functions in Quantum Mechanics
I am trying to learn about Green's functions as part of my graduate studies and have a rather basic question about them:
In my maths textbooks and a lot of places online, the basic Greens function G ...
2
votes
1answer
199 views
A question about definition of Fermi energy
Wikipedia states the definition of Fermi energy as for "a system of non-interacting fermions". If we have to assume free electrons in a solid behave this way before we are able to calculate Fermi ...
4
votes
1answer
322 views
Can surface dipoles/charges change the work function of a metal?
As typically drawn in simplified band diagrams (see picture below), the metal Fermi Level is shown as the top of the conduction band, with the entire band filled.
In many situations, including ...
3
votes
1answer
183 views
What are Low-lying energy levels?
I am reading about some canonical transformations of the Hamiltonian (of a system consisting of an electron interacting with an ionic lattice) due to Tomanaga and Lee, Low and Pines. One of the ...
3
votes
2answers
785 views
Why electrons are relativistic in Graphene and non relativistic in vacuum?
If a free region in space has a potential difference of one volt, an electron in this region will acquire kinetic energy of 1 eV. Its speed will be much smaller than the speed of light hence it will ...
5
votes
1answer
187 views
Question concerning the Lindhard function
I'm having a question concerning the Lindhard function.
The reference I'm using is the standard text "Quantum Theory of Solids" by Charles Kittel.
I'm concerned with Chapter 6, subchapter "Method of ...
4
votes
0answers
126 views
What happens to a Luttinger liquid under time reversal?
Suppose you a have an ordinary Luttinger liquid with
$$ H = \int dx \sum _{\eta= \pm 1 , \sigma =\uparrow,\downarrow } \psi^\dagger_{\eta, \sigma} (x) (-i v \eta \partial _x) \psi _{\eta,\sigma} (x). ...
3
votes
1answer
298 views
How does thermal broadening of the Fermi Function cause electron coherence loss?
Generally, there are two ways for electrons to lose their wave-like properties in a solid material. One is by way of collisions that cause changes in the energy and momentum of the electron. The other ...
0
votes
1answer
77 views
References for the source and application of bonding-antibonding splitting on electronic structure?
I am currently doing research on semiconductor materials, so I need a very strong background in band theory to understand the literature. I am currently trying to understand the relationship between ...
5
votes
4answers
2k views
Chemical potential
This is something probably very basic but I was led back to this issue while listening to a recent seminar by Allan Adams on holographic superconductors. He seemed very worried to have a theory at ...
11
votes
2answers
416 views
Is there a method for differentiating fractional quantum Hall states aside from finding Chern numbers?
The ground state for a quantum Hall system on a torus with fractional filling factor can be classified by the Chern number, which is why the Hall conductance is quantized. Is there another method or ...
