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.

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Valence bands question

I'm currently doing solid state physics and learning about semiconductors. During the course, I have seen a lot of energy/wavevector graphs, like this one (pic from Kittel): I did not have a ...
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Band-gap for solids with isoelectronic atoms

Isoelecronic atoms have same number of electrons but different nuclear charge. It is said that many of the chemical properties of these elements are equal or at least similar. Can I form solids with ...
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291 views

Why are HCP materials brittle whie FCC materials are ductile?

Why are hexagonal close packed materials brittle, While face centered cubic is ductile. Is it related to crystal planes?
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Role of density of states of electrons in a solid

When studying the statistical mechanics of a solid such as a conductor or a semi-conductor, does the density of states of electrons play a role in the calculation of the heat capacities? I know that ...
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25 views

Mapping the first Brillouin zone to the nth Brillouin zone

The Brillouin zone can be constructed in the reciprocal lattice, by drawing bisectors to the lines that connect near neighbors. For example in the 2-D square lattice, the first Brillouin zone in red ...
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14 views

Why phenomena in different energy scale can be treated separately?

For example, there are electrons and lattice vibration in solid. The order of energy of electron is of eV which is much larger than that of lattice vibration. So they can be treated separately which ...
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72 views

Effects of massive magnetic field generated by operation of the large hadron collider?

I read an article about the CERN large hadron collider in which it talks about the magnetic field that is generated while the LHC is operating. A magnetic field more than 100,000 times more powerful ...
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79 views

Do metals *really* conduct at zero temperature?

The questions is mostly in the title, but might expose another of my misunderstanding of the band structure of solids and how that leads to metals and insulators. If we have a solid, and the fermi ...
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32 views

Landau levels in ferromagnets

Consider a spontaneously magnetised (uniformly) conducting ferromagnet. Now suppose that there is no external magnetic field. The question is as follows: will the motion of electrons be quantized via ...
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115 views

Why liquids and solids are mostly regarded as incompressible?

In many continuum-mechanical Problems it is assumed that liquid and solid substances cannot Change the total value of volume where it holds $\rho = const, \vec{\nabla}\cdot \vec{v} = 0$. In the ...
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41 views

Coulomb potential of a periodic crystal in reciprocal space

Usually the Coulomb potential (electron-electron interaction) can be Fourier transformed (aside from prefactors) like that: $$ \frac{1}{|\vec r_1 -\vec r_2|} = \int \frac{\text d ^3 k}{(2\pi)^3} ...
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96 views

If something is infinitely thin can it cut through anything? [closed]

Not sure if I heard this somewhere or how I came up with this idea but would something infinitely thin object be able to cut through everything effortlessly? For example, if I had a knife with its ...
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52 views

Heat capacity of solids

In the Einstein/Debye models, the specific heat capacity goes as T^3 at low temperatures and approaches the Dulong-Petit law at higher temperatures. I undestand that some molecular motions (rotation, ...
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59 views

different energies for the same k vector for free electrons in a solid

when we use the nearly free electron approximations for electrons in a solid and get them as plane waves the energy becomes $E=\frac{\hbar^2k^2}{2m}$, which gives us a parabola. but when we see the ...
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1answer
96 views

Density of States in NOT Free Electron Gas

I think that I understand how the density of states works for a free electron gas. It is effectively just a conversion factor between summing over values of k and integrating over values of E. If you ...
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82 views

Reduce integration over crystal to integration over unit cell

I am wondering when I can reduce integrals over a periodic crystal to a an integral over the unit cell. Especially I consider the following two-electron integral $$ I=\langle \varphi_i \varphi_j | V | ...
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52 views

Density of states and elliptic integral

It is known, for example Equation (14) in the graphene review of Castro Neto (arXiv), that the full expression for the density of states (DOS) of graphene is in terms of an elliptic integral. Close ...
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Why aren't most ionic/covalent/metallic materials self-healing?

For the most part, only soft-matter materials appear to possess self-healing capabilities (that is, if I cleave the material and then press the two halves together, the material re-forms) at room ...
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38 views

Is hysteresis essential for a memory system or material?

I want to know whether its essential for a memory system or material to have hysteresis between two of its variable ? If Yes, what can be the general relation of volatility of a memory with its ...
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2answers
79 views

Density Functional Theory (DFT) tutorial guide

I am going to start learning about DFT calculations. Could anyone advise me the best starting point for that? Simple example guiding tutorial with explanations would be great. Any input would be ...
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70 views

Tight binding on sawtooth 1D lattice

I am reading the paper "Bose condensation in flat bands" (arXiv). The authors consider a tight-binding model on the one-dimensional "sawtooth" lattice, comprised of two sites A and B in the unit cell ...
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87 views

Number Conserving Superconductors

Usual BCS theory used to describe superconductors violates particle number conservation, this is allowed since that theory is written in a grand canonical ensemble (i.e particles can be exchanges ...
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31 views

Why the Kondo effect is important for STM?

The Kondo effect is observed when approaching 0K. Why would this effect be important for STM?
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169 views

Non-uniqueness of the k-vector in Bloch state

How to understand that Bloch wave solutions can be completely characterized by their behaviour in a single Brillouin zone? Given Bloch wave: \begin{equation*} \psi_{\mathbf{k}}(\mathbf{r}) = ...
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3answers
154 views

Primitive unit cell of fcc

When I consider the primitive unit cell of a fcc lattice (red in the image below) the lattice points are only partially part of the primitive unit cell. All in all the primitive unit cell contains ...
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1answer
13 views

Why the centered rectangualr lattice is not considered a special case of an oblique lattice

From Wikipedia, there are 5 different kinds of lattice in 2 dimension: But I am wondering how the third type (the centered rectangular) is different from the first kind (the oblique lattice). The ...
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lattice vibration

I would like to inquire about acoustic and optical branch in Phonons vibration; My question is: what is the physics description when we say what is make acoustic and optical branch appear ...
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76 views

Do solids have translational energy?

Along with having vibrational energy, do both crystalline and amorphous solids also have translational energy? I ask because I've always understood solids to have just vibrational motion/energy. But ...
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What determines the Bloch wavepacket length scale?

We know in the semiclassical Boltzmann theory, there are several length scales: the lattice constant $a$, the Bloch wavepacket spread $\xi$, other length scales such as the mean free path $l$, the ...
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Tuning the frequency in graphene

As is well known, the frequency of transverse optical phonons in single layer graphene ranges from $10^{11}$ to $10^{12}$ Hertz. How can one "tune" the frequency to a specific value?
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Synthesis of Fe-based superconductors

Polycrystal cuprate superconductors are generally prepared by solid state reactions: Starting reagents are in powder form, they are mixed to each other and placed into furnace on high temperature ...
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42 views

Why does the stiffness of organic polymers (plastic) change so much with small changes in temperature?

This is on the borderline between Physics and Chemistry, but I would like a Physics perspective. I am guessing that plastics are a glass-like phase, rather than a true solid.
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32 views

Why is metal stiffer at lower temperatures?

Each morning I cycle to school and lock my bike with a thick steel wire (about 8 mm thick). I noticed that it's much harder to change the shape of the wire in the morning when it's much colder than ...
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2answers
82 views

Is it possible to mix a drink with a non-standard phase of ice?

Would it be possible to safely cool and drink a glass of water with anything else than the Ih form of ice? Here and here you can see that some alternative forms of ice have a higher density than ...
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What are the key differences between a Wigner crystal and charge density wave?

We know that Wigner crystal is a crystal formed due to interaction(kinetic energy is quenched). It is a crystal of electrons and therefore has periodical oscillations in the charge density. Therefore ...
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30 views

Connection between Lindhard susceptibility and Free energy

I've encoutered a few times, but I never got an explanation for it... How is the spin-dependent Lindhard function for the dynamical susceptibility of an electron gas $$ \chi_{\sigma,\sigma'} (q, ...
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31 views

What is the “point” of STM?

Scanning tunneling microscopy (STM) measures density of states (DOS) in a sample. But angle-resolved photoemission spectroscopy (ARPES) measures the bandstructure $E(\mathbf{k})$ in a sample, from ...
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What is the meaning of band structure in the case of amorphous materials?

A consistent band structure is expected in crystals, because "everything is uniform". Theoretical calculations of band structure are also based on infinite lattice. In amorphous materials, however, ...
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66 views

Wavefunction for Anti-Pfaffian state

What is the most general form of a wavefunction for anti-Pfaffian in variables $\{z_i\}$ which represent the positions of electrons on a two dimensional plane?
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101 views

Does the Mermin-Wagner theorem forbid superconductivity in the 2D Hubbard-Model?

"In the 2D Hubbard model (two spatial dimensions) the Mermin-Wagner theorem does not allow a phase transition." I am quite illiterate concerning this theorem and hearsay. Does the theorem apply to a ...
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1answer
42 views

Conservation of crystal momentum with Peierl's substitution

I am trying to understand Sec. 3 of Di Xiao's review paper (http://arxiv.org/abs/0907.2021). Specifically, I am interested in Sec. 3A on anomalous velocity (pages 13-14 in the arXiv pdf). I can ...
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29 views

Do the fourier components of a periodic function need to satisfy the boundary conditions imposed on it?

I cannot understand the opening statement of the second derivation of Bloch's theorem in the solid state physics book by Ashcroft and Mermin (Chapter 8, eqn 8.30). We start with the observation ...
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45 views

Analysis of a Fermi surface

The following image shows the Fermi surface of Pb, plotted with XCrySDen. I have some difficulties in uderstanding the characteristics of that Fermi surface, in particular how to distinguish the ...
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285 views

Many Body Physics: Hamiltonian block structure and Symmetries

Consider a many body problem of a small cluster, e.g. the 'Hubbard-Cluster' (albeit the question may be of relevance for other Hamiltonians as well): $$\mathcal{H}=\sum_{<ij>\sigma} t_{ij} ...
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1answer
74 views

Are acoustic phonon frequencies always linear in k?

I'm confused by a discussion in Ashcroft and Mermin's textbook on pg. 512-513. They say that if we have a bunch of ions in a solid and neglect the effect of the conduction electrons, then waves will ...
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41 views

Underdoped Cuprates

What does underdoped cuprates mean? I guess cuprate is underdoped when hole concentration is less then optimal doping. Am I Right?. or it is something difference?
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How to do continuum approximation?

Assume you have $N$ matrix fields $T_{j}$ on a 1d lattice with lattice constant unity. Now consider a sum like the following (you can think of the traces as supertraces), and subject it to a continuum ...
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29 views

Symmetry in program for ewald summation

The formula for Ewald summation as given in Allen and Tildesley - $$ U = U^{(r)} + U^{(k)} + U^{(bc)} + U^{self} $$ where the k-space contribution of potential is given by $$ U^{(k)} = \frac{1}{\pi ...
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1answer
61 views

Quasi-fermi levels in a solar cell?

I was wondering, if my fermi levels splits up due to n and p type doping into two fermi levels, one for the p type one for the n type, and now due to light radiation my fermi levels split up into 2 ...
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35 views

potential decomposition in terms of Bloch eigenstate

Given a single particle Hamiltonian $H=-\frac{\hbar^2}{2m}\nabla^2+V(r)$, where $m$ is the electron mass and $V(r)$ is a periodic function representing the lattice potential. It is defined in the ...