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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Why do some things crystallize? (And others don't, for that matter.)

Ice, for example, will form a crystal when frozen under certain circumstances. Why is this the case for ice? While on the subject of water crystallization, why do snowflakes usually form in base 6 ...
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Does it make sense to define the mean free path in quantum mechanics?

The mean free path defined in classical molecule dynamics has a strong classical flavor. Is it sensible to generalize the idea to quantum mechanics?
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Can plasma turn back into gas, solid, or liquid?

I wanted to know if, since basic chemistry teaches you that states of matter can be changed, I was wondering particularly about plasma. I know that virtually all of the Sun is plasma, so I was ...
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Why are periodic boundary conditions used for the derivation of phonons? [duplicate]

I am currently reading "Quantum Field Theory for the Gifted Amateur". In chapter 2 Phonons are introduced as solutions (in k-space) of a coupled harmonic oscillator. In real space the oscillator is ...
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162 views

Origin of High-temperature Superconductivity

What is the mechanism that causes certain materials to exhibit superconductivity at temperatures much higher than around 25 kelvin?
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666 views

Can Ohm's law break in metals?

I was rereading Purcell's Electricity and Magnetism as research for another question, and I found this passage: In metals Ohm's law is obeyed exceedingly accurately up to current densities far ...
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The Spectral Function in Many-Body Physics and its Relation to Quasiparticles

recently, I stumbled accross a concept which might be very helpful understanding quasiparticles and effective theories (and might shed light on an the question How to calculate the properties of ...
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How to calculate the properties of Photon-Quasiparticles

in recent questions like "How are classical optics phenomena explained in QED (Snell's law)?" and "Do photons gain mass when they travel through glass?" we could learn something about effective ...
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How should I be thinking about phonons?

I have started learning solid state physics and i am struggling with the concept of phonons. I understand how the vibrational wave can be quantised (because of quantum oscillators) and thought of as ...
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102 views

After being heated and cooled why does Coconut Oil form these structures?

According the the guy who posted this picture, the coconut oil melted during a heatwave and then re-solidified into hexagonal structures. I looked into foam physics and it seems that area deals ...
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624 views

Why is effective mass of holes positive?

i am trying to understand this. I know that the effective mass of electrons or holes is calculated as: $$m^* = \frac{h^2}{(4\pi^2)\frac{d^2E}{dk^2}}$$ Now,if i look at this plot for example: I ...
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Why does the n=0 Landau level in graphene have half the degeneracy of the other levels?

I've looked through several papers that talk about the anomalous integer quantum Hall effect of graphene (such as http://journals.aps.org/prl/pdf/10.1103/PhysRevLett.95.146801), and they all state ...
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466 views

Why does the Fermi Surface cross the Brillouin zone boundary at right angles?

I'm not sure why the fermi surface crosses the Brillouin zone boundary at right angles. I understand that this is normally the case, but not necessarily always. I'm aware that the fermi surface is a ...
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Optical absorption — what are the common ranges and mechanisms?

So let's say you do some reflection/transmission spectroscopy of a material. It's clear that it's absorbing in some range. What would be your first step in identifying the source of the absorption? ...
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590 views

Divergent issue of Madelung's constant

This is a question triggered by this post Madelung's constant is defined to the coefficient of electrostatic potential energy in a ionic crystal. In the example of $NaCl$, \begin{equation} M = \sum_{...
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Meaning of the 'deep lattice limit' and 'shallow lattice limit'?

In condensed matter literature, at many places, the phrase 'deep lattice limit' is used. Please tell what is the deep lattice limit and the shallow lattice limit?
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682 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?
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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 ...
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Mobile “muonic hydrogen”

If we look at the atomic positions in a single crystal sample with a diamond like lattice, there exist directions along which there are long hexagonal "tubes" (I'm not sure if these have a proper term)...
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Lattice geometry and dispersion relation

Is there a general theorem which gives some information about which influence have the lattice geometry (for example sub-lattice structure, square lattice, honeycomb lattice, lattice symmetries, ...) ...
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“Bosons are either gapped or condensated, except physical principle protected cases (Goldstone boson, photon).”?

Bosons are either gapped or condensated, except physical principle protected cases (Goldstone boson, photon, etc.). I read this in a paper (version1 of http://arxiv.org/abs/1404.3728v1, 1st page 1st ...
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Optical mode leakage through a layer of gold

The geometry of my semiconductor device is given below. The blue regions are gold, the grey ones - gallium arsenide (n-doped to $2.9 \times 10^{15} \mathrm{cm^{-3}}$). The dimensions are μm, i.e. it ...
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476 views

Why isn't there a potential difference across a disconnected diode?

I know this question sounds silly, as if there was a potential difference a current would be created when the terminals are connected together and this would mean energy has come from somewhere. The ...
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900 views

Paramagnetism Spin-1/2 Particles - Partition Function

I'm trying to come up with an expression for the partition function of a system of spin-1/2 ideal gas particles on a line of length $L$. The total number of particles $N$ is fixed, with $N = N_\...
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Higgs vs phonons

Jim Baggott's "Higgs" quotes David Millers' prize-winning one-page explanation of the Higgs mechanism (the one that evokes Margaret Thatcher crossing a room). I've heard that part many times, but not ...
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Yet another question on the Lindhard function

Here's another question concerning the Lindhard function as used in the physical description of metals. First we define the general Lindhard function in the Random Phase approximation as $\chi(q,\...
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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 ...
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540 views

What is the boundary condition of graphene flake with zigzag edges?

It is a question about free carrier behavior in graphene flakes. (or may be called charge confinement) Say if we have a perfect hexagonal free standing graphene flake terminated with zigzag edges. ...
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What is injection level (semiconductor physics)?

I am currently reading journal articles about semiconductor physics in solar cells. What is injection level? I'll try to start off with what I understand. Photons hitting the silicon cause its ...
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What happens to a radar signal when it meets with a superconductor? [duplicate]

A radar system has a transmitter that emits radio waves called a radar signal, consisting of electromagnetic radiation. What happens when it meets with a strong superconductor, considering the fact ...
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Lattice parameters and basis vectors of crystal lattice structures

Does someone know where I can find lattice parameters and basis vectors of crystal lattice structures (Strukturbericht Designation) for different materials? In particular I am searching the lattice ...
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704 views

Peierls substitution vs minimal coupling

In the presence of vector potential (let's assume it's uniform), a tight-binding Hamiltonian will be changed according to the Peierls substitution: $$t_{ij}c_i^{\dagger}c_j \to t_{ij}e^{iqA|i-j|}...
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760 views

A (smart) way to map out the Brillouin zone of a 2-D material

I am currently writing a tight-binding calculation model for various 2-D cells as part of a homework assignment. Whilst solving the problem set was quite easy I struggle at a smart way to plot the ...
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779 views

Pauli paramagnetism for electrons with external magnetic field

Apparently it is to be shown that for electrons under an external magnetic field, in the limit as $B\to 0 $ $$ \chi = \frac{dM}{dB} \approx \frac{n\,\mu^{*^2}}{k\,T}\,\frac{f_{1/2}(z)}{f_{3/2}(z)} $$ ...
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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). ...
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How is Meissner effect explained by BCS theory?

Someone says we can derive the GL equations from BCS theory, which can explain Meissner effect, but I want a more clear physical picture of this phenomena.
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Sign of the hopping integral in tight binding model

The Hamiltonian of tight binding model reads $H=-|t|\sum\limits_{<i,j>}c_i^{\dagger}c_j+h.c.$, why is there a negative sign in the hopping term?
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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!
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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 ...
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Different electrons, why aren't they all the same?

Why do we say that there are different kinds of electrons when discussing different situations in physics? For instance the Weyl electron, Dirac electron etc. From my exceedingly basic knowledge isn't ...
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Why is copper diamagnetic?

Cu has an unpaired electron in 4s, but it is diamagnetic. I thought that it has to be paramagnetic. What am I missing?
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For the transition metals, how does counting the number of up-spins and down-spins still give you a non-integer magnetic moment?

The transition metals like Fe, Co and Ni have magnetic moments of 2.2, 1.7 and 0.6 Bohr magnetons, respectively. The band theory says that you get this when you calculate the density-of-states of the ...
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How can a material conduct heat but not electricity

Mica is a good conductor of heat but an electrical insulator. According to free electron theory (which applies only to metals) free electrons carry heat and electricity. Therefore, thermal ...
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Topological insulators literature

I started learning things on topological insulators and I got lost in dozens of existing papers on this topic. Could anyone recommend me appropriate literature that explains deeply enough what ...
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Why does $c_{-k,-\sigma}$ create a particle with momentum $k$?

In Mudelung's book, Introduction to Solid-State Theory, I am confused by the following statement. For many applications a further simplification is helpful. The concept of the hole presents us ...
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If you suddenly move a piece of metal, will that disturb the free electron density?

If we have a hollow pipe sitting at rest filled with gas and we moved the pipe suddenly along its length to the right, then the gas density will be momentarily higher near the rear of the pipe and ...
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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 ...
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Reflection, Transmission, and Plasma Frequency

Does anyone have a good, clear explanation of why and how this works? I don't understand the following. Say you have a piece of metal with a plasma frequency $\omega_p$. This is like a resonant ...
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Is the superconducting current made up of Cooper pairs?

Inside the superconductor it should be $\mu_0\mathbf{j} = \mathbf{\nabla} \times \mathbf{B} = 0$, since B is 0 due to the Messner effect. This means that the current is carried by the surface. But ...
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Proof that all primitive cells have the same size

A primitive cell of a crystal lattice is a set $A$ such that two copies of $A$ which are translated by a lattice vector do not overlap and such that $A$ tiles the entire crystal. I have read (for ...