Questions tagged [condensed-matter]

The study of physical properties of condensed phases of matter, including solids and liquids.

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The cavity method of Ising model in infinity dimension and dynamical mean field

In the article "Dynamical mean-field theory of strongly correlated fermion systems and the limit of infinite dimensions" chapter III.A, when discussing the cavity method of Ising model, the ...
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EM Lorentz force field flux in the air gap of a parallel plates charging capacitor?

For a charging/discharging capacitor, simultaneously to the electric field created by the displacement current during charge/discharge cycle, a magnetic field is also generated in the area inside the ...
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Magnetic unit cell in Hofstadter model

What is the best way to choose magnetic unit cell in the Hofstadter model for any $p/q$, the magnetic flux enclosed by a unit cell in the flux quantum unit $h/e$ in order to solve the eigensystem in ...
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Spectral flow in IQHE

I am encoutering some problems in understading the argument in David Tong's QHE lecture notes that the spectral flow of extended states give rise to currents in IQHE. First, Tong argues in page 36 ...
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Open boundary condition in hubbard model

In case of open boundary condition, crystal momentum is not a good quantum number anymore. I mean we can construct an $N×N$ matrix in position basis and diagonalize it to obtain the eigenvalues, but ...
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Hartree-Fock vs. density functional theory

What is the relationship/difference between the Hartree-Fock method and the density functional theory? It seems the basic formulations of them are very similar.
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Could you magnetize and at the same time elactrostatically charge a piece of rusted iron?

Pure iron rust (i.e. iron oxide) can be electrostatically charged and also magnetized. In a piece of iron usually the surface starts rusting leaving the interior untouched. Is it possible to have such ...
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Can you magnetize iron by putting it in the air gap of a two parallel plates capacitor?

We can magnetize an iron piece (i.e. permanently given enough field strength) by putting it inside a solenoid strong homogeneous field and charging/discharging the solenoid several times. I am asking ...
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Is there a consensus of experimental evidence amongst scientists of whether spin-charge separation exists in 2d?

I am looking for a very simple qualitative, definite answer of whether there has been a legitimate experimental evidence of spin-charge separation in 2D. This is for a presentation for one of my ...
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What is the signal velocity in a very thin enameled magnet wire?

I was wondering if in the case of a very thin enameled (i.e. sub-millimeter thick wire insulation dielectric usually made from polyimide) magnet wire the generated electric field of a signal transient ...
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Hamiltonian and Lagrangian in Condensed Matter

Can metal can be described as sum of many particle Lagrangian rather than Hamiltonian?
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I have found a serious error in a Wikipedia page? [duplicate]

From WP Signal Velocity article: https://en.wikipedia.org/wiki/Signal_velocity Signal velocity is usually equal to group velocity (the speed of a short "pulse" or of a wave-packet's middle ...
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How to harvest water passivley?

I have been reading recently about methods to collect moisture from the air passively and turn it into water. However, is there any attempt currently for small-scale water harvesting? Methods I have ...
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Hartree-Fock on a lattice: how to deal with non-diagonal charges

For a Hubbard hamiltonian, $$\hat{H} = \sum_{i,j,\sigma} t_{i j} \hat{c}^\dagger_{i \sigma} \hat{c}_{j \sigma} + \sum_i U_i \hat{n}_{i \uparrow} \hat{n}_{i \downarrow}, $$ the mean-field solution can ...
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How to use Density Functional Theory to get the correct energy spectrum

I'm having some trouble understanding how DFT can be used to obtain results for electronic structure calculations. We can assume that we're studying an $N$ electron atom with a fixed nucleus and want ...
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Frequency Integration of Green's Function

If one has a Green's Function that has been projected into the Helcity basis (from spin) of the from \begin{equation} G(\mathbf{k},\omega)=\sum_s\frac{1}{\omega-\epsilon_{\mathbf{k},s}+\mu+isgn(\omega)...
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Did I understand RG correctly?

I am currently self-studying Renormalization Group (RG) in Condensed matter physics (in preparation for graduate school while I'm in Alternative Military Service). While I'm writing bunch of ...
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"Universal" versus "nonuniversal" in the topological entanglement entropy

In their seminal paper, Kitaev and Preskill consider a 2D area law for entanglement of the form $$ S(\rho) = \alpha |\partial A| - \gamma + \cdots. $$ Here $\rho$ denotes the density matrix associated ...
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Incredible electron drift velocity in atomic thin layer of graphene?

Free electrons in atomic thin layers of graphene behave more like photons (Bosons) than fermions reaching incredible drift velocities and mobility which reach speeds as reported by this article in the ...
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What can cause charge density wave (CDW) in 3D metal except for fermi surface nesting?

As we know, the charge density wave (CDW) naturally happens in 1D metal at low temperature due to Peierls instability. It also happens when you have fermi surface nesting in 2D or quasi 2D metal. But ...
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Plausible finite group on-site-SPTs in realistic materials

I am looking for some understanding of which on-site symmetries in realistic crystalline materials (i.e. not just in random lattice models) can plausibly be expected to be realized and to induce ...
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How to test for possible negative mass of dark matter?

What is the phenomenology of how to test if dark matter has possibly a negative mass (WP negative mass) in particle physics experiments, cosmology or astrophysics? I lately came across this ...
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Why does doping allow for Cooper pairs in high temperature superconducting cuprate compounds in Resonating Valence Bond Theory?

Preface: I'm a first years masters student (only in my second quarter) and I'm well aware that RVB theory is an extremely complex and high level topic. I have to give a presentation for one of my ...
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Momentum and position representation of BCS Hamiltonian

I am struggling to relate the BCS Hamiltonians in momentum and position representations. The free part of the BCS Hamiltonian is often written $$ H_{\text{pos}} = \int d^3 r ~ \psi^\dagger(r) \left(\...
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What's a charge density wave?

I'm reading chapter 2 of Condensed Matter Field Theory by Alexander Altland, Ben D. Simons, Section on Interacting fermions in one dimension. From what I understood, they considered the system of ...
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Why superfluid He-4 exhibits one degree of freedom zero viscosity but when for example rotated has a non-zero viscosity?

It is shown clearly in this demonstration that He-4 superfluid has zero viscosity for a one directional flow (i.e. one degree of freedom in motion) but shows viscous behavior when a more complex ...
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Tuning fork quality factor measurement using SR 830 lock-in amplifier

I've read about some methods based on SR 830 to conduct measurement on tuning fork Q, such as https://arxiv.org/abs/1809.01584. But I am wondering can I use the sine output signal directly as ...
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Resource recommendation for time-dependent DMRG

I am looking for any references (journal article/ review /tutorial) to understand the TEBD (Time-evolution by block decimation) algorithm and code it up for a simple 1D model system. Broadly, I am ...
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Can the water remain in the vapor gas form at zero Kelvin (0K) temperature? (when the pressure is low enough or under other conditions)

Naively, when the water cools down to low temperature, the water goes to the ice solid phase. (Like below 0 celsius at 1 ATM pressure.) Can water remain in the gas form at zero Kelvin (0K) temperature,...
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Why not all Berry phase just vanished?

I just learned that for any real wavefuntions, berry phase equals zero. But in Griffiths' Problem 2.1(b), he proved that any complex wavefuntion can be written as linear combination of REAL ...
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Ginzburg Landau model from Usadel equation

I have been learning how to obtain the Ginzburg-Landau model (local theory) starting from the Eilenberger equation (microscopic theory). I recently come across the Usadel equation which is obtained ...
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Number of maxima of 1D many-body fermion density

Consider in quantum mechanics a single particle in one dimension, with a Hamiltonian $$ H_0(x) = -\frac{\hbar}{2m} \frac{d^2}{dx^2} + V(x). $$ It is well known that the $n$:th bound eigenstate $\psi_n(...
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Static dielectric constant and optical dielectric constant

I was reading Introduction to Solid State Physics of Charles Kittel (8th Edition), and the static dielectric constant is defined as $$\epsilon(0) = \epsilon(\omega=0) $$ and the optical dielectric ...
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Is Bogoliubov transformation simply a basis transformation?

I encounter Bogoliubov transformation when I'm learning 1D transverse field Ising Model.But I think it's just a simple basis transformation, I don't understand why people give it a special name?
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Why electrons that form the cooper pairs only lie within $\omega_D$ of the Fermi energy in superconductors?

In BCS theory, it's said that electrons that form the pairs only lie within $\omega_D$ (Debye frequency) of the Fermi energy. Why is that? Edit - In Quantum field theory for the gifted amateur, ...
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Diagonal long range order

I heard a lecture given by Professor Liu Haiwen. He said: off-diagonal long range order(ODLRD)$\rightarrow$BEC diagonal long range order(DLRD)$\rightarrow$solids ODLRD+DLRD$\rightarrow$supersolids ...
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What is the mass of collective oscillations?

When you step through the procedure of deriving a phonon dispersion relationship for a given crystal structure (i.e. small oscillations from equilibrium, harmonic approximation, collective coordinate ...
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Matrix components of energy of simple cubic crystals

Im working through the derivation of the paper by Slater and Koster (1954) http://users.wfu.edu/natalie/s15phy752/lecturenote/SlaterKoster.PhysRev.94.1498.pdf Im having trouble working through table 2....
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Applying Kramers-Kronig to the real part of conductivity results in a real and imaginary term

Following Tinkham's Introduction to Superconductivity, the complex conductivity in the two-fluid approximation is defined as \begin{equation} \sigma_i(\omega)\equiv\sigma_{1i}(\omega)-i\sigma_{2i} \...
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Why silver atom is diamagnetic and aluminium paramagnetic although both have one valance unpaired electron?

According to theory all atoms that have one unpaired valance electron are paramagnetic and all atoms which have no unpaired electrons are diamagnetic. Transition elements atoms like iron which have ...
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Symmetry breaking in near free electron?

In 1D lattice, if we consider a near-free electron model, ie. $$\hat{H}=-\hat{\psi}^{\dagger}(x)\frac{\nabla^2}{2}\hat{\psi}(x)+V(x)\hat{\psi}^{\dagger}(x)\hat{\psi}(x)$$ where $V(x)$ is a periodical ...
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Representation of one-body operator in field theory

Section 2.1 Introduction to second quantization, Page No 47 of Condensed Matter Field Theory reads Representation of operator (one-body) Single-particle or one-body operator $\mathcal{O}_1$ acting in ...
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Questions regarding physical electronics [closed]

I ran into some questions while studying physical electronics. My textbook/lecture note says "An electric field applied to a semiconductor will produce a force on electrons and holes so that ...
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Composite fields and statistics

The usual explanation for superconductivity is that the electrons form Cooper pairs, which are bosons. This effective boson then condenses. E.g., quoting Wikipedia, Therefore, unlike electrons, ...
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Spectral unfolding for Aubry-Andre model

While I was studying on random matrix theory recently, I have tried to unfold the spectrum of Aubry-Andre model. If the amplitude $\lambda$ of quasiperiodic onsite potential is less than 2, then it is ...
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Iridium carbides in stainless steel alloys

Has there ever been any high carbon stainless steel made with iridium as one of the alloy components? Is there any research in this direction? There is a paper from 2016 comparing various iridium ...
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How to derive the equations of motion of finite temperature Green function?

I'm having a trouble deriving the equation of motion of a Green function. My understanding of the derivation is the following. Given a set of fermionic creation annihilation operators $$\{a_\alpha (\...
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Para- and ortho-excitons in solids with spin-orbit coupling

The names para- and ortho-exciton stem from the fact that -- in superficial analogy to para- and ortho-hydrogen -- the wave function that forms the electron-hole bound state can either be a singlet ...
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Why Hamiltonian for a Solid is periodic in Bloch Theorem?

It is as simple as the title and more general to Bloch theorem treatment. In any periodic infinite solid lattice, we say that the potential will be periodic. This makes sense, but how do we know that ...
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Units of Berry curvature/connection elements in Wannier90 code

If you please have a look at Eq. (25) of Vanderbilt's PRB2006 paper, the gauge transformation of the connection element $A$ results in $A^{(H)}_\alpha = \bar{A}^{(H)}_\alpha + iD^{(H)}_\alpha $, $\,\,...
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