The study of physical properties of condensed phases of matter, including solids and liquids.
Questions tagged [condensed-matter]
4801 questions
18
votes
2 answers
The difference between the Wannier function and atomic orbit in a tight binding model
In a tight binding model, we usually start from the atomic orbits and linearly combine them to get the wave function of the crystal energy band.
My questions are:
Since this kind of tight binding is an approximate method due to using atomic orbits,…
Laurent
- 595
18
votes
2 answers
Fermi surface nesting and CDW/SDW/SC orders
Fermi surface nesting and CDW/SDW/SC orders.
What is the definition of a nesting vector?
And why Fermi surface nesting gives rise to different orders at $T=0$?
(CDW: charge density wave; SDW: spin density wave; SC: superconductivity)
Machine
- 1,935
- 1
- 15
- 29
17
votes
3 answers
What is an "incompressible" quantum liquid?
What does "incompressible" mean in the context of an incompressible quantum liquid?
leongz
- 3,966
15
votes
3 answers
Why are so many condensed matter phenomena so dependent upon impurities?
Why are so many condensed matter phenomena so sensitive to impurities? In fact, quite a number of them depend upon impurities for their very existence!
jsp
- 151
15
votes
1 answer
What is the meaning of the diamagnetic current in linear response theory?
When we consider the response of a quantum lattice model with Hamiltonian $H=H_{kin}+H_{int}$ to an applied vector potential $\mathbf{A}(\mathbf{r},t)$ we obtain the current operator $\mathbf{j}(\mathbf{r})$ by expanding the kinetic energy…
Fitzgerald Creen
- 534
12
votes
2 answers
A question about Haldane's conjecture
Haldane's conjecture states that the integer spin antiferromagnetic Heisenberg chains have a gap in the excitation spectrum. However, the dispersion relation of the antiferromagnetic spin wave is $\omega_k\sim k$ in the long wave length limit,…
user16064
12
votes
1 answer
What conductance is measured for the quantum spin Hall state when the Hall conductance vanishes?
It's probably just a definition, but what did König et al. actually measure when he confirmed
the existence of surface states in CdTe/HgTe/CdTe quantum wells (see http://arxiv.org/abs/0710.0582)?
According to most reviews (e.g.…
Mike
- 672
- 1
- 8
- 15
10
votes
1 answer
How likely is it that metallic hydrogen is metastable at atmospheric pressure?
I just watched a news report about the laboratory production of [solid] metallic hydrogen for the first time. I was surprised to find the researchers predicting that, once produced, it might remain solid at atmospheric pressure. The video says they…
N. Virgo
- 33,913
9
votes
3 answers
What does an electron's wavevector mean inside of a crystal?
With a plane wave, I always took the direction of the wavevector, $k$, as the direction of propogation (magnitude proportional to the inverse wavelength). Alternatively, it could represent the momentum (minus a factor $\hbar$) of a particle.
However…
Brendan
- 270
8
votes
2 answers
The Nambu spinor
What is the reason behind using the weird minus sign in the fourth component of the extended Nambu basis?
$$\Psi^{\dagger}=(\Psi_{i\uparrow}^{\dagger}\quad \Psi_{i\downarrow}^{\dagger} \quad \Psi_{i\downarrow}\quad-\Psi_{i\uparrow})$$
While it does…
Arnab Barman Ray
- 668
8
votes
1 answer
meaning of $k$ in $k\cdot p$ approximation in condensed matter physics
Sometimes, I encounter such a practice in condensed matter literature:
One takes a $k\cdot p$ hamiltonian $H(k)$ and substitute $k$ for $\nabla_r$, and then he solves the equation: $H(\nabla_r)\psi=E\psi$. Here is some example:
In graphene,…
atbug
- 1,421
8
votes
4 answers
I found it strange in case of an egg omlette
Its known to everyone that when a solid is heated up to its melting point it turns into a liquid. What happens when a liquid is heated? Simple, it tends towards becoming gaseous.
While making omlettes I found that the yolk is in liquid state and…
Primeczar
- 529
7
votes
1 answer
Why is the Efimov effect only seen in 3d systems?
I have been reading about the Efimov effect, which is that a system of three identical bosons has a particular excitation spectrum, including a bound state, independent of the underlying interaction and even if there aren't any two-body bound…
user2820579
- 773
7
votes
1 answer
Glass and isotropy
Glasses are amorphous materials. Nevertheless, as far as I know, in some areas of Condensed Matter, they consider that the glass is isotropic. Under what restrictions they can do this assumption?
Mathematically, the assumption that glasses are…
Rodrigo Thomas
- 1,028
6
votes
1 answer
$\theta$ term of anomaly related with topological insulators
I am reading Ludwig's paper "Electromagnetic and gravitational responses and anomalies in topological insulators and superconductors", and in this paper, although I am clear how they get the descent equation which introduced the relationship between…
huyichen
- 801