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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Non-constant Bandgap in a semiconductor

For a material made of two different intrinsic semiconductors (SC); $SC_A$ on the left, and $SC_B$ on the right, such that $E_{gap,A}>E_{gap,B}$, the energy band diagram would look like so: Note: ...
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Is it possible to have solid light? [closed]

Is it possible to have solid light? If so, what would it be like?
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How are you the special points/critical points in the Brillouin Zone pronounced? [closed]

I know that this isn't exactly physics, but I don't know where to ask. http://en.wikipedia.org/wiki/Brillouin_zone#Cubic_lattice_system_CUB.281.29.2C_BCC.281.29.2C_FCC.281.29 The critical points/...
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Electronic or excitonic band structure?

Usually, in the papers the electronic band structure for monolayers $WS_2$ is something like in the figure below: As you can see the direct bandgap is around ~2.0 eV. When we excite electrons at the ...
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Direction of momentum given by the de Broglie relation

The momentum of an electron can be computed by the well-known classical mechanics equation: $p=mv$ where $m$ is the mass of an electron, and $v$ is its velocity. In this case, since $v$ is a vector,...
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Is zero heat capacity possible without violating the third law of thermodynamics?

Suppose we have a gapped system i.e. no gapless excitation is possible. If the thermal energy is insufficient to excite atoms from ground state to excited state of any kind (of a single atom or of a ...
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Miller indices and distance between parallel planes in a cubic lattice

I have been learning about the Miller indices of a lattice plane and how to use them to find the distance to the nearest parallel lattice plane in a Cubic lattice but I must be getting something wrong....
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Dispersion relation for lattice vibrations: Why are there two and not four solutions?

A linear chain of diatomic molecules can be modeled by a chain of molecules with different spring constants $C_1$ and $C_2$ (See Figure) The corresponding equations of motion are: $$M\ddot{u}=-c_1[...
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Why does the band gap decrease when the thickness of the material increases?

Thin films of material (monolayers, etc) tend to have higher band gaps than their bulk materials. This is true for a wide range of materials. What is the reason? Is it due to the fact that there is ...
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Experimental confirmation of the finite jump of the occupation number at the Fermi surface

It is a well-known result in Fermi-liquid theory that the occupation number has a finite jump at the Fermi surface. But, is it confirmed experimentally?
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Why are numbers not consistent? (Identifying phonon's frequency)

I am trying to connect several facts between each other to acquire a consistent picture. Fact 1. Monolayers of tungsten disulphide $WS_2$ have hexagonal crystal lattice, and the first Brillouin zone ...
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Fluctuation-dissipation theorem in QFT

If I understand correctly, the fluctuation-dissipation theorem (fdt) in QFT technically arises because of $\pm i\epsilon$ - infinitesimally small summand in the denominator of spectral representation ...
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Is it feasible to store large amounts of information on DNA molecules (for years)?

This initially might seem like a biology based question, but I want to concentrate on the physics of DNA molecules, used purely as a manmade stable substrate for storing information. A 2013 Ted Talk ...
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Question about the Luttinger liquid

I am learning Luttinger liquid now. It is a very basic question, I think. Look at the figure. For each $k $, there is a state for the left mover and a state for the right mover, right? They have the ...
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Solutions for Kittel's Introduction to solid state physics 6th edition?

I'm looking for the solutions of Kittel's 'Introduction to solid state physics' 6th edition. I can only seem to find the solutions for the 8th edition online. Does anyone have the pdf to it? Or ...
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Is this a valid way for deriving the ODE for a lattice vibration of a one dimensional crystal?

Consider the following lattice: I want to derive a differential equation that describes the forces acting on the $n$-th atom in the lattice. Each atom is coupled to its neighbour ($n+1,n-1)$ by a ...
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Why can the dispersion relation for a linear chain of atoms (connected by springs) be written as $\omega(k)=c_s \lvert k\rvert$?

On the german wikipedia site (right under "Akustische Moden"), the dispersion relation for a linear chain of atoms (connected by springs): $$\omega(k)=2 \sqrt{\frac{K}{M}} \left \vert \sin{\frac{ka}{...
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How one can count how many phonon modes is there in the crystal?

I'm reading the review on phonon and Raman scattering in 2D transition metal dichalcogenides (2D TMDCs). At the beginning of Section 2.1 it is said that, since there are two X-M-X units in the crystal'...
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Springs, elastic potential energy, kinetic energy

If a ball with some kinetic energy collides with a spring, the ball doesn't lose its kinetic energy in an instant, right? it loses kinetic energy as the spring gains potential elastic energy. Right? ...
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Derivation of effective mass equation in carbon nanotubes

I am trying to reproduce the calculations in the paper here by Ando and Nakanishi and am already stuck on equation 1. It is stated that in the vicinity of $\epsilon=0$ the amplitude of the ...
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bare Phonon and Symmetry Breaking

In condensed matter physics, the phonon is considered as a quasiparticle which is a result of the quantization of lattice vibrations. In many textbooks on solid state physics, it can be done if we ...
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What is the name of basis states of bulk k.p Hamiltonian?

A k.p Hamiltonian for a bulk material can be represented by 8x8 matrix in basis of $|S\uparrow\rangle$, $|S\downarrow\rangle$, $|X\uparrow\rangle$, $|Y\uparrow\rangle$, $|Z\uparrow\rangle$, $|X\...
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quantum and thermal fluctuations in 1D, 2D, 3D

Why do thermal and quantum fluctuations destroy long-range order in 1D and 2D? Why not in 3D? If the answer is quite elaborated (with many formulas) perhaps a reference would be better. Sorry if this ...
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Why thermal conductivity increases with temperature?

what is the molecular mechanism with which thermal conductivity increases by increasing temperature? at least for metals? I know that heat increases the oscillations of the atoms in the crystal. But ...
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What's the conductivity of graphene nanostructres (nanoribbon, nanomesh)?

As we know, the conductivity of graphene can be expressed with Kubo formula,including intra transition and inter transition. But does graphene nanoribbon or graphene nanomesh have the same ...
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P-n junction diode under forward bias configuration

Why there is exponential growth in current with respect to voltage in p-n junction diode under forward bias configuration?
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Is Mott insulator the same as non-compressible quantum fluid?

In the field of ultracold quantum gases we study the so called Bose-Hubbard model given in second quantization: $$\hat{\mathcal{H}} = -t\sum_{\langle i,j\rangle}\hat{a}^{\dagger}_{i}\hat{a}_{j} + \...
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Is there a way to measure the thickness of a metallic plate of order of micrometers?

I have a $5 cm×5 cm×? \mu m$ copper plate. Where '$?$', the thickness of the plate, is really small (about 30um). Is there anyway using physics to calculate the thickness? Update: Sorry I forgot ...
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Is diamagnetism a static or dynamic effect?

When we put a diamagnetic material in the presence of an external magnetic field $\vec B_0$, the magnetic field inside the material decreases to $$\vec B=(1+\chi_m)\vec B_0,$$ where the magnetic ...
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Microscopic interpretation of magnetization in a 2D electron gas

I'm studying the de Haas-Van Alphen (dHvA) effect in a 2D free electron gas, and I have a problem to interpret the microscopical meaning of the flip of magnetization during the dHvA oscillation. My ...
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What is space charge Capacitance of diode?

Most of the books say that $p$-type and $n$-type materials of diode act as parallel plates of space charge capacitance were as the depletion charges (uncovered) act as dielectric. Then why do these ...
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How should I interpret the x-axis of an electronic band structure diagram ? Is it the direction an electron is moving?

Recently I've come in contact with electronic structure diagrams for my thesis and I have some difficulties getting an intuitive interpretation of reading these diagrams. What I think is happening: ...
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Is disturbance propagation velocity equal to wave velocity in a solid body?

How do the disturbance propagation velocity and wave propagation velocity relate to each other? To explain my question in details I will describe the following situation from the theory of acoustic ...
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Can conducting electrons in a metal be modeled at all as classical particles?

I have seen computational models that treat the highest energy electrons in a conducting metal as classical particles in a plasma, the ions being held in place with some sort of heuristic nearest-...
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Free charges inside a conductor and propagation of EM wave

In Griffith's book on Electrodynamics, while discussing the propagation of electromagnetic wave in a conducting medium, he set $\rho_{free}=0$. He argues that, any extra charge given to the conductor ...
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Calculating the matrix element for interband absorption

I am reading the book by Fox 'optical properties of solids'. In chapter 3, he considers the interband absorption of photons in an direct band solid. It is necessary to calculate the matrix element ...
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Notations for high symmetry points in the 1st Brillouin zone

I am trying to understand how I should interpret the letters like Г,K,M,T etc., that are usually there in the electronic band structure diagrams. So, let's assume we have graphene with its hexagonal ...
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What is the lattice sum and how can I calculate it for a general reciprocal lattice vector?

In lecture we were given the following definition: Lattice sum $$\sum_{n=1}^N e^{-i \mathbf{Q}\mathbf{R}_n}$$ where $\mathbf Q=\mathbf k-\mathbf k'$ is the scattering vector. First question: What ...
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Lattice sums (solid state physics)

The potential in a crystal doesn't only depend on the distance between 2 atoms, but also with the interaction to all $j^{th}$ neighbour-atoms. The Lennard-Jones-Potential then becomes $U(R_j)=\...
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X-ray diffraction: Is there an intuitive explanation of structure and form factors?

We have just started x-ray diffraction and I am utterly lost. We were given two formulas: First formula: The intensity of the x-rays scattered by $\mathbf{Q}=\mathbf{k}-\mathbf{k}'$ is given ...
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what is elastic thickness?

I read the article about Flexural rigidity, it says Flexural rigidity of plates is defined as $D=\dfrac{Eh_e^3}{12(1-\nu^2)}$ and $E$ is the young's modulus, $\nu$ is poisson's ratio. And I can't find ...
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Database for work functions for exotic crystallographic faces

Is there a database, which holds work functions (found either from experiment or calculations) for some more exotic crystallographic faces, such as (221) or (311) for copper? I dug around and found ...
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Relationship between fracture of solid plates and its curvature

I do some school projects about fracture of glass, my assumption is this phenomenon related to the curvature of these plates, specifically, fracture starts from the point which is having “maximum” ...
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It it true that the Fourier transform of the return probability can be written as the product of the retarded propagator & the advanced propagator?

I know the retarded green's function $G(r,r; E)$ is expressed as $$G(r,r; E)=\sum_n \frac{|\mu_n(r)|^2}{E-E_n+i\eta}$$ with the eigenvectors/eigenvalues $\mu_n(r)/E_n$. This expression of $G(r,r; E)$ ...
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Fermi surface reconstruction and fermi pockets

Certain quantum phase transitions are characterized by the emergence of some ordering wavevector $K$ : antiferromagnetism, charge or spin density waves, among others. In the case of Néel ...
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What exactly is the reciprocal lattice and how is it connected to the Ewald sphere?

I want to understand what the reciprocal lattice is and how it is connected to the Ewald sphere. I know a very similar question has been asked on this site already: Reciprocal lattices. The top ...
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What does it mean that a Cooper pair behaves as a boson but respects the obligations of fermions?

I refer to the fact that it has integer spin, but antisymmetric wavefunction. How is this possible?
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Why the bandgap of inorganic semiconductors decreases with temperature?

The temperature dependence of the energy bandgap in inorganic semiconductors is given by $$E_g (T) = E_{g,0} - \frac{\alpha T^2}{T+\beta}$$ where $\alpha, \beta$ are both positive, and the (somewhat ...
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what is the effect of temperature on the resistance of a photoconductor?

As we know, for a photo conductor resistance tends to decrease with increase in irradiance, but with greater irradiance comes greater temperature. Also we know, photo conductors are semiconductors,...
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How does negative power lead to amplification?

I am currently investigating semiconductor superlattices and I am analyzing the negative differential velocity (NDV) after a certain limit. I understand how NDV leads to negative power, but I am ...