Tagged Questions
2
votes
1answer
24 views
Origin of interaction in inelastic neutron scatting
In solid state physics, inelastic neutron scattering is a commonly-used experimental technique for probing the energy spectrum of phonon and magnon excitations. This technique relies on the ...
7
votes
2answers
170 views
Ferromagnetism with mobile spins
How can electron spins in Iron at room temperature have ferromagnetic order even though they are travelling at very high speeds?
One could argue that spin and motion are completely uncorrelated and ...
3
votes
0answers
57 views
What is the difference between spin glass and spin liquid?
What is the difference between spin glass and spin liquid?
Do they both originate from frustration?
1
vote
1answer
38 views
If my lattice has an atomic basis, do I also find the reciprocals of the basis vectors to get the reciprocal crystal structure?
That is what my crystal structure looks like. The blue atoms sit on every lattice point (basis vector of $\{0,0\}$) and the red atoms have basis vector of $\left\{{2\over3},{1\over3}\right\}$. The ...
2
votes
1answer
42 views
Is this 2D structure triclinic?
The only rotation axis obvious to me is rotation by 360 degrees, the identity. Vertical mirror planes I've been dicing and cutting it through several planes and I still see none. Yet, the structure ...
1
vote
1answer
41 views
What would be the basis vectors for this 2D crystal structure?
In the above image, I have a 2D crystal structure. The lattice vectors are described by:
a = {-1/2, -Sqrt[3]/2};
b = {1, 0};
and the location of atoms A and B ...
2
votes
3answers
98 views
What is the difference between lattice vectors and basis vectors?
Google has not been very useful in this regard. It seems no one has clearly defined terms and Kittel has too little on this.
3
votes
1answer
41 views
Dopant concentration and changes in band gap energy
Thanks to this lovely website, I was able to pop out reasonable values for my band gap energies from a translucent material. As expected, I found a decrease in band gap energy due to my treatments.
...
0
votes
0answers
23 views
What are some applications of crystal fabrication? [closed]
I have heard of some applications here or there in certain papers, but I am looking for a broader scope of examples.
0
votes
1answer
42 views
Influence of the temperature on the ionization energies for impurities in silicon
Is there any dependence of the impurities ionization energy on temperature in silicon? I mean if there are any interactions between localized electron and phonons which leads to renormalization of ...
4
votes
2answers
135 views
Graphene +1 extra carbon bond
I'm not a physicist just a curious mind, so please go easy!
I was just watching a BBC Horizon Documentary that featured a piece on the recently discovered material Graphene. One of the facts ...
2
votes
2answers
71 views
Are electronic wavefunctions in band gap insulators localized? is a single-particle picture sufficient in this case?
I am having trouble understanding the physics of band gap insulators.
Usually in undergrad solid state physics one looks at non-interacting electrons in a periodic potential, with no disorder.
Then, ...
3
votes
1answer
96 views
Fermi level with Landau levels
So my question is regarding where the Fermi energy is when you have 2D electron gas in an applied magnetic field. My book explains that, using the Landau gauge, you find that the 2D density of states ...
0
votes
1answer
101 views
Calculation of Number Density
Number density equation is given by
$ n= \dfrac{(N_A)\rho}{M} $
where
$ N_A =6.023\times10^{23} mol^{-1} $
$ \rho=8.02\ g/cm^3 $(at 1500 degree celsius.)
$M=63.546*1.6605\times10^{-24} g$
Whats ...
2
votes
0answers
59 views
Why do Fermi liquids have T^2 resistivity?
I have often read that metals that are Fermi liquids should have a resistivity that varies with temperature like $\rho(T) = \rho(0) + a T^2 $.
I guess the $T^2$ part is the resistance due to ...
0
votes
0answers
96 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 ...
3
votes
1answer
106 views
Graphene with a disclination and the spin-orbit coupling
I am trying to follow the methods used in this paper (http://arxiv.org/pdf/1208.3023.pdf) to construct the Hamiltonian of a graphene cone, but taking into account the spin-orbit coupling.
The paper ...
1
vote
2answers
99 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
$$\operatorname ...
0
votes
0answers
106 views
Phonon Momentum
I am reading Charles Kittel's solid state physics and wondering what's the mechanism that neutron waves and photons can interact with phonons and the process obey the generalized momentum-energy ...
1
vote
2answers
72 views
What are some ways of inducing spin polarization?
I saw a talk today and they mentioned how nitrogen-vacancy diamond centers can be used to optically induce spin polarization and now I wonder what other ways there are to induce a spin polarization.
...
1
vote
1answer
102 views
Semi-conductor band-gap and deformation potential
Submitting a semi-conductor to stress leads to a deformation in the energy-bands, roughly described by:$$H_{ij} = {\cal{D}}_{ij}^{\alpha\beta}\;\epsilon_{\alpha\beta}$$
$\epsilon$ being the strain ...
0
votes
0answers
29 views
Residual symmetries of the superposition of two fcc lattices
Fcc lattices are Bravais lattices and so are invariant under a set of discrete translations plus inversions over the 3 axis ($x\rightarrow -x$,$y\rightarrow -y$,$z\rightarrow -z$). When one superposes ...
0
votes
0answers
18 views
Rice Allnatt distribution function
Can anyone give me an article of which explains Rice Allnatt distribution function or can you explain the function here?
4
votes
1answer
61 views
Where to learn Temperature Dependent Conductivity induced by Electron-Phonon Interaction? [closed]
I want to learn how to calculate the temperature dependent conductivity induced by electron-phonon interaction.
I know in low temperature, the resistance in metal $\rho$ is proportional to $T^5$, $T$ ...
1
vote
1answer
468 views
Effective Mass and Fermi Velocity of Electrons in Graphene:
In graphene, we have (in the low energy limit) the linear energy-momentum dispersion relation: $E=\hbar v_{\rm{F}}|k|$. This expression arises from a tight-binding model, in fact $E =\frac{3\hbar ...
1
vote
1answer
142 views
Energy spectrum of a tight-binding model
Consider the one-dimensional tight-binding Hamiltonian
$$\mathcal{H}=t\sum_m\left(a^\dagger_m a_{m+1}+a^\dagger_{m+1} a_{m}\right).$$
With the lattice constant set to 1, the energy spectrum is given ...
2
votes
2answers
113 views
Why is a critical system equal to a gapless system?
In condensed matter physics, people often say that a system without energy gap is a critical system. What does it mean?
Any help is appreciated!
3
votes
1answer
210 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 ...
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
176 views
Simple model of edge states for a two-dimensional topological insulator
Quantum spin Hall states or, topological insulators are novel states of matter that have insulating bulk and gapless edge states. Are there any simple models that show these features?
See e.g. the ...
1
vote
1answer
182 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 ...
1
vote
0answers
65 views
How to derive the divergence leading to Kohn anomalies?
I'm trying to understand the mathematical derivation given in the book "A Quantum Approach to Condensed Matter Physics" on page 215 (see 1), for explaining how the phonon-energy perturbed by ...
4
votes
1answer
237 views
What does “particle number conservation” mean in condensed matter physics?
What exactly does it imply about a condensed matter system to have particle number conserved or not conserved?
For example, why does the superconducting phase break particle number conservation while ...
1
vote
1answer
77 views
What papers detail the early research on heavy fermion superconductors?
Can someone point me to the papers detailing when/where/how heavy fermion superconductors were first synthesized, tested and documented?
1
vote
2answers
183 views
Thomas-Fermi approximation and the dielectric function (+ small bit on graphene)
1) With the dielectric function, which is a function of wavenumber and frequency,how is it possible to take the limit of either to zero without changing the other one? I thought that frequency and ...
2
votes
2answers
127 views
What's the differences among the concepts: binding energy, cohesive energy and formation energy?
In the papers about first principles (or ab initio) calculations, there are three energies which are often calculated: "binding energy", "cohesive energy" and "formation energy". Their meanings are ...
3
votes
1answer
79 views
Inelastic Scattering and coherent scatterng
Another Scattering Question
So I have this Bravais Lattice of sites R vibrating with some normal mode with a small displacement amplitude $u_o$, some wave vector k and some frequency $\omega$. We can ...
2
votes
1answer
169 views
Inhomogeneous Effective Mass in a 2D Lattice
Consider a tight-binding square lattice in 2D. This lattice has two different nearest neighbor tunneling rates along the x and y directions; call them $J_{x}$ and $J_{y}$. All longer range tunneling ...
0
votes
1answer
59 views
1D Acoustical Relations beyond nearest neighbor couplings
Consider some 1D Lattice of atoms with nth neighbor coupling of strength k_{n}. I'm looking for the dispersion relation for acoustical phonons under these conditions.
I start with the Lagrangian,
...
2
votes
1answer
233 views
The Hendriks-Teller Model
So I am working on understanding the Hendriks-Teller model of 1D disorder. So the way I understand it is the following. You have a random smattering of particles. Each mass is separated by some unit ...
4
votes
0answers
130 views
What is the mass of the emergent magnetic monopoles in spin ice and how is the mass of an emergent particle determined?
In solid state physics emergent particles are very common.
How one determines if they are gap-less excitations?
Do the defects in spin ice called magnetic monopoles have mass?
What is the mass of ...
1
vote
1answer
105 views
Does anyone know the difference and relation between $k\cdot p$ method and tight binding (TB) method?
Among the methods of calculating energy bands for crystals, first-principles method is the most accurate. Besides first principles, two commonly used modeling methods are the $k\cdot p$ method and ...
0
votes
0answers
32 views
Can one obtain saturation magnetization from FMR measurements?
Especially for magnetic thin films. Normally this is done by magneto-optical Kerr effect or SQUID measurements. Or is there a way to calculate the saturation magnetization based on other measured ...
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) ?
...
6
votes
1answer
211 views
Temperature dependence of resistivity in metals
We know that in high temperature, resistivity in metals goes linearly with temperature. As temperature is lowered, resistivity goes first as $T^5$ due to "electron-phonon" interaction, and then goes ...
1
vote
1answer
156 views
Formation of the overlap in metal electron bands
I understand that metals have overlapping of valence and conduction bands. But is this because there exists a partial conduction band within the top part of a metal valence band, or because the ...
3
votes
0answers
83 views
Qualitative argument to determine energy of defects
In a book of "LES HOUCHES - Critical Phenomena, Random systems, Gauge theories" the author Frolich says that:
2D
In two dimensions, the mean energy of an isolated point defect in a square area of ...
2
votes
1answer
85 views
What is the difference between contact-limited and space-charge-limited charge transport?
I am reading a paper ("Tunable Electrical Conductivity of Individual Graphene Oxide Sheets Reduced at 'Low' Temperatures," Jung, et al. Nano Lett. 2008, 8, 4283-4287) about electrical conductivity in ...
4
votes
1answer
504 views
The Difference between Thomas-Fermi Screening and Lindhard Screening
Assuming the general theory of screening related to electron-electron interactions, I was wondering if anyone could provide a clear, yet conceptually complete explanation of the differences between ...
