Tagged Questions
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 ...
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.
2
votes
1answer
155 views
Specific heat capacity of a 2D free electron gas
I have got so far the 2D density of states as $g(\epsilon)=\frac{Am}{\pi\hbar^2}$ where $A$ is the area of the "square" and $m$ is the the electron mass. Then I have found an expression for the the ...
0
votes
1answer
103 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 ...
6
votes
2answers
149 views
Why does the quantum Heisenberg model become the classical one when $S\to\infty$?
The Hamiltonian of the spin $S$ quantum Heisenberg model is
$$H = J\sum_{<i,j>}\mathbf{S}_{i}\cdot\mathbf{S}_{j}$$
I have read that when the spin quantum number $S\to\infty$, quantum fluctuation ...
0
votes
1answer
71 views
Momentum change in colisions (Drude Model)
A particle suffers elastic colisions with scattering centers with a probability of colision per unit time $\lambda$. After a colision the particle is in a direction caracterized by a solid angle ...
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 ...
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,
...
0
votes
0answers
37 views
Off-center vortex
If we have a off-center vortex with strength $n$ in a superfluid contained in a cylindrical container (with distance $r$ away from center), the angular momentum is determined from the following ...
3
votes
0answers
295 views
Goldstone modes and Heisenberg model
The ideia is to show that, because of Goldstone modes, 2d systems are quite different from 3d ones. So, considering the Heisenberg model, I'll post here what I'm asked to and my current thoughts on ...
4
votes
1answer
508 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 ...
2
votes
1answer
163 views
True Ground State Population of Ideal Bose-Einstein Condensate at Critical Temperature
I'm supposed to demonstrate that although we make the assumption in an ideal BEC that the ground state population follows
$N_0 = N\left[1-\left(\frac{T}{T_c}\right)^{3/2}\right]$
in reality the true ...
1
vote
0answers
164 views
Electron Fermi gas
My question is about 2-dimensional Fermi gas of electrons.
What is magnetic susceptibility when $T<<T_F$ (where $T_F$ is Fermi Temperature)
and,
What is the ratio between Pauli and Curie ...
