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

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Numerical Tools to find Braiding Statistics of Quasiparticles

While certain classes of systems that exhibit topological order can be solved exactly (such as the Toric Code, Abelian FQH Edges, etc.) there also exist systems (think of perturbed versions of the ...
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1answer
32 views

Fetter & Walecka's derivation of second quantised potential term in many-particle TDSE

For the potential term in the Hamiltonian, I understand that we go through the same process as with the kinetic energy term. On the RHS of the TDSE, we get something like ...
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126 views
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123 views

Is Planck’s proof of Kirchhoff’s Law of Thermal Emission false; and if it is not false why is it not false? [on hold]

In his book ‘The Theory of Heat Radiation’, Max Planck adduced his theoretical proof of Kirchhoff’s Law of Thermal Emission. However, there are some problems with that approach, some of which we ...
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1answer
25 views

Calculate the laser heating on a crystal

Let's say I'm doing an optical experiment. I focus a laser on a crystal with a certain amount of power. The crystal's temperature is regulated to a certain temperature but it is localy heated by the ...
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1answer
34 views

General properties of Matsubara frequency summations

By properties, I mean linearity, shifting, commutativity, etc. I was hoping to evaluate something like $S_\eta = \dfrac{1}{\beta}\displaystyle\sum_{i\omega} g(i\omega)$ where $g(i\omega) = ...
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1answer
29 views

Why does a dynamical gauge field accompany fractionalisation?

I'm trying to understand fractionalisation, of which spin-charge separation is an example. I've read that this is accomplished by introducing a Lagrange multiplier field, which becomes a dynamical ...
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1answer
155 views

How to prove Bloch function is periodic in reciprocal lattice?

How to prove Bloch function is periodic in reciprocal lattice? I saw in some textbooks this formula: $$ \Psi_{\mathbf{k}} (\mathbf{r}) = \sum_{\mathbf{G}} ...
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422 views

Momentum change in collisions (Drude model)

A particle suffers elastic collisions with scattering centres with a probability of collision per unit time $\lambda$. After a collision the particle is in a direction characterized by a solid ...
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296 views

Quantum Hall Effect and Edge States

In quantum hall effect we measure the hall conductance (in transverse direction) which is quantized. My question how do they take care of the edge states that are in the longitudinal side?
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312 views

How to understand topological order at finite temperature?

I have heard that in 2+1D, there are no topological order in finite temperature. Topological entanglement entropy $\gamma$ is zero except in zero temperature. However, we still observe some features ...
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698 views

How does Haldane conjecture follow from the topological $\Theta$ term

The one dimensional SU(2) Heisenberg quantum spin chain is known to be described by the 1+1d O(3) nonlinear $\sigma$ model with a $\Theta$ term, following the action ...
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17 views

What is the difference between quantum and classical Heisenberg model?

I have been studying these models very closely. I see that when we go from classical to quantum Heisenberg model we replace spin vectors with Pauli matrices. I don't understand the reason behind it. ...
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40 views

What is the correct statement of Kirchhoff's Law of Thermal Emission?

There are various quite different statements in textbooks and other science literature as to Kirchhoff's Law of Thermal Emission. So, what is the correct statement of Kirchhoff's Law of Thermal ...
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27 views

Density of states for graphene

I have seen a lot of plots for the density of states for graphene: but have been unable to find the calculation explicetely. I know the dispersion relation for graphene is $E_{\pm} (\textbf{k}) ...
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37 views

In what circumstances, can exchange interaction acquire temperature dependence?

Heisenberg exchange interaction (sometimes called as magnetic stiffness?), originating from the Coulomb interaction and the Fermion statistics, is widely used in theories of magnetism. Conventionally, ...
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1answer
26 views

Can the probability of electron capture in a metal hydride be increased by extreme electric current?

An example of a metal that can hold a lot of hydrogen is palladium. The hydrogen atoms (protons) in the metal lattice are positive and the electrons are negative. When a large electric potential is ...
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1answer
103 views

How is superconducting coherence length measured in experiment?

In a superconductor, the coherence length measure the mean distance between two electrons in the Cooper pair. How is the coherence length experimentally measured?
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1answer
206 views

Why is the projective symmetry group (PSG) called projective?

As discussed by Prof.Wen in the context of the quantum orders of spin liquids, PSG is defined as all the transformations that leave the mean-field ansatz invariant, IGG is the so-called invariant ...
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1answer
45 views

Self-energy of a Fermi liquid

A weakly correlated many-electron system can be viewed in a first approximation as a Fermi liquid, meaning that it behaves similarly to a non-interacting electron gas with renormalized parameters. In ...
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25 views

Weyl semi metal vs entanglement entropy

In 2+1D, entanglement entropy (EE) is crucial for identifying a topological phase. What happens in 3+1d case? e.g. what are the behaviours of EE in WSM and trivial states?
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51 views

Why is amorphous classified solid?

Because it does not have a crystal structure, it is hard to find physical similarities with a solid. Why isn't it then another state other than solid? The physics of amorphous is also quite different ...
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225 views

What kinds of behavioural anomalies can a zero-field-cooled (ZFC) / field-cooled (FC) split indicate?

If a material shows a spiltting in the ZFC and FC curves, is it necessarily superparamagnetic, or could there be any other reason for the irreversibility? I have heard spin glasses also show ZFC-FC ...
3
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1answer
162 views

Will Anderson's Poor Man's Scaling loose its effect when band width is small?

The s-d interaction Hamiltonian is as fellows $H_I=Js.S$, J is the coupling strength. We focus on the antiferromagnetic case, where $J>0$. According Anderson's poor man's scaling, the ...
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1answer
22 views

What's the difference in the film between sputtering deposition and an ebeam evaporator?

I know the differences between the two deposition techniques, but what about the difference in the properties of the resulting films? All things being equal (such as substrate temperature), would ...
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2answers
51 views

Variant of the Sokhotski–Plemelj theorem

I am aware of the Sokhotski–Plemelj theorem (I have also heard people referring to it as the "Dirac identity") which states that in the limit $\eta\rightarrow 0^+$ $$\frac{1}{x\pm i\eta}=\mathcal ...
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1answer
119 views

Topological invariant for interacting systems using single particle green functions?

Why Single particle green's function is (preferred) used to find topological for interacting systems? $N_1 =\frac{\epsilon_{ijk}}{24 \Pi ^2} \int dw d^3k G \partial_i ...
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275 views

Is there any relation between temperature dependence of resistance and fermi energy in metals?

Given that the resistance varies linearly with temperature in metals, is there any way we can calculate the Fermi energy from this information?
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228 views

Has anyone experimentally shown the quantized thermal hall conductivity in Quantum Hall systems?

For background: In a $D=2+1$ state with edge modes described by a chiral $( c_L \neq c_R )$ CFT there is a predicted thermal Hall conductance associated with the gravitational anomaly at the edge. ...
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1answer
435 views

Quasi 1D insulators with strong spin-orbital interaction

We know that the spin-1 chain realizes the Haldane phase which is an example of symmetry protected topological (SPT) phases (ie short-range entangled phases with symmetry). The Haldane phase is ...
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62 views

What are fragmented condensates?

It is defined that if more than one eigenvalue of the one-body density matrix are macroscopically occupied the condensate is said to be fragmented. $$ n^{(1)},n^{(2)},...=\mathcal{O}(\mathcal{N}) $$ ...
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1answer
154 views

Looking for a good introductory-level review of pseudopotential methods

I'm looking for a good introductory-level review of pseudopotential methods. In particular, I'd like to understand how the self-consistent pseudopotential methods work.
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59 views

Fetter & Walecka's derivation of second quantised canonical Schrodinger equation for fermions

On page 18, before the occupation number variables for states i and j are changed $n_i \rightarrow n'_i = n_i - 1$ and $n_j \rightarrow n'_j = n_j + 1$ respectively, could we not have rewritten eq. ...
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2answers
140 views

What is the physical significance of the Curie constant?

What is the physical significance of the Curie constant? I understand it depends on the effective moment of the ion and hence must be some measure of it, but what is it exactly? Like some average ...
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19 views

How well can ADSCFT related approaches to condense matter predict measurable properties of materials? [closed]

Are ADSCFT techniques able to make any predictions about measurable properties of any materials? Are there some interesting but somewhat accessible looking problems left in this area to solve or is ...
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20 views

Non-equilibrium electronic distribution in the time-relaxation approximation - Which is the boundary condition?

In Chapter 13 of Ashcroft-Mermin - "Solid State Physics", the following non equilibrium electronic phase-space distribution for the semiclassical electrons in a periodic crystal is derived: ...
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1answer
121 views

Kronecker sum or direct sum?

When we write $$H=\sum_k H_k$$ in condensed matter physics, are we using Kronecker sum or direct sum? I think this is direct sum. However, Wikipedia says it is Kronecker sum. Can anyone give some ...
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35 views

How to describe spin-orbital coupling in Weyl semi-metal

In three dimensional Weyl semi-metal, the Hamiltonian that describes low excitation quasi-particle is well-know Weyl Hamiltonian: +/- $k\cdot\sigma$. But if I want to add spin-orbital coupling in that ...
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47 views

Transfer from Heisenberg to Ising model

It is well know, that ferromagnets can be described using Hamiltonian $$ H = -\sum\limits_{i<j}J_{ij}\, (\mathbf{s}_i \cdot \mathbf{s}_j). $$ where (three dimensional) spins $\mathbf{s}_i$ ...
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1answer
237 views

Superconductivity in graphene with spin orbital coupling, is it proper to let the order parameter on two sub-lattice equal?

I am reading this article: Edge superconducting correlation in the attractive-U Kane-Mele-Hubbard model. Considering just the first part of the article, where a negative-U Hubbard model with the ...
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1answer
50 views

Difference between $\nu=5/2$ quantum Hall state, chiral p-wave superconductor, He 3

I am interested in the relation between the following three phases of matter (in 2D): chiral $p$-wave superconductor (spineless $p_x + i p_y$ pairing) $\nu=5/2$ fractional quantum Hall state A-phase ...
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11 views

What is our most complete microscopic theory for the elastic-plastic transition point?

I suppose its all stated in the title. What is our most successful description of the microscopic behavior of material at the elastic-plastic transition point. My condensed matter physics prof was ...
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1answer
157 views

Point group symmetries and unit cell

I was wondering if the unit cell (of a given lattice) had to have every point group symmetries of the lattice it defines ? I guess there is no unique way to define a unit cell and that it may not have ...
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21 views

Quantum spin Hall effect and the edge states

In quantum spin Hall effect or Kane-Mele model, how can one get rid off the edge states without affecting the bulk?
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1answer
34 views

behavior of dissolved ionic compounds in an electric field

Consider the following setup - An open, insulating box is filled with distilled water, into which is dissolved a significant amount of pure NaCl. Two insulated lumps of conductor, one with a large ...
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1answer
411 views

What is a Dirac semimetal?

What is the precise definition of a Dirac semimetal? Is it sufficient for two bands to touch at a single k point with a linear crossing, or are more conditions required for a material to be called a ...
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42 views

Electron self-energy calculation for a $k$-dependent interaction

I am trying to calculate the Fock term of an electronic self energy in the Matsubara formalism : Where the straight black line in the free electronic Green's function : $G_{k+q}(i\omega_n + i\nu_n) ...
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1answer
201 views

Do indirect optical transitions “cool” the material a little?

So I'm reading in Ashcroft and Mermin about indirect optical transitions: So, a photon comes in, and it only excites the electron across the indirect band gap if a phonon with the appropriate wave ...
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1answer
286 views

Atomic nearest neighbor notation

I recently got a correction to a paper that I am writing. The correction references a section in which I talk about nearest neighbors. The comment says: Do you mean NN, NNN, etc., or NN, 2NN, 3NN? ...
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Do tensor product tables for irreducible representations apply for non-symmorphic space groups?

I'm reading Dresselhaus's book on group theory for solid-state physics, but I'm having trouble understanding how to get irreducible representations for phonons away from $\mathbf{k} = \mathbf{0}$ for ...