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

learn more… | top users | synonyms

0
votes
0answers
38 views

Question(s) Regarding the Lindhard Function

As a theoretical chemist, I'm slightly outside of my element on a project my advisor gave me, so I come to your for help and direction. Basically, he wants me to integrate the imaginary part of the ...
0
votes
1answer
44 views

electron shell jumping in Iron?

I understand a "little" about electron shell jumping, I was wondering about "Iron", If iron was heated to a gas, perhaps held in a vacuum maybe even under pressure, would the added energy make the ...
1
vote
0answers
41 views

Proof of periodicity of Floquet Green's function

It is claimed in many papers that the two-time Green's function in time periodic Hamiltonian case is periodic in the average time, i.e. \begin{equation} G(t+T,t'+T)=G(t,t') \end{equation} when ...
1
vote
1answer
341 views

Symmetry arguments for valley physics in graphene with broken inversion

I am trying to understand this paper: http://link.aps.org/doi/10.1103/PhysRevLett.99.236809 (Here is an arXiv version: http://arxiv.org/abs/0709.1274) In the introduction, they mention certain ...
4
votes
1answer
386 views

Finding the ground state of the toric code Hamiltonian

How do I write by proof, the ground state of the toric code (by Kitaev) Hamiltonian $ H=-\sum_{v}A(v)-\sum_{p}B(p) $ where $A(v)=\sigma_{v,1}^{x}\sigma_{v,2}^{x}\sigma_{v,3}^{x}\sigma_{v,4}^{x}$ and ...
0
votes
0answers
27 views

Charge and spin susceptibility in the random phase approximation

In the random phase approximation, the charge and spin susceptibility (of a Hubbard model, for example) can be written as $$\chi^c(q) = \chi^0(q)\left[1+U^c\chi^0(q)\right]^{-1},$$ $$\chi^s(q) = ...
0
votes
0answers
20 views

Energy magnetization in the presence of temperature and chemical potential gradient

In the following paper (Phys. Rev. Lett. 97, 026603) http://journals.aps.org/prl/abstract/10.1103/PhysRevLett.97.026603 the energy magnetization part of the energy current is given in the presence ...
3
votes
1answer
418 views

Naive questions on the ground states of Kitaev model

I got some naive questions on the ground states of honeycomb Kitaev model (with open boundary conditions): (1) Consider a simple case that $J_x=J_y=0$, then the model reduces to $$H=J_z\sum_{z\text{ ...
3
votes
1answer
104 views

Is there a bulk signature of topological nontriviality for a 3D free fermion band insulator?

Is there such thing as a 3D Chern invariant (or some other quantity) that I can use to test an insulating quasiparticle spectrum is a topologically trivial or non-trivial insulator? Does one exist ...
2
votes
2answers
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 ...
1
vote
1answer
80 views

Why Integer Quantum Hall Effect (IQHE) can only happen in even dimensions?

I read that Integer Quantum Hall Effect (IQHE) can only exist in even dimensions, while Quantum Spin Hall Effect (QSHE) can be generalized to 3D (or rather any dimensions?). Does anyone have a ...
1
vote
0answers
17 views

Coupled Diff Equation from Bose Einstein distribution [closed]

I am a student doing physics hons and have had very little experience in programming. This semester we are supposed to do a computational project in thermodynamics. I have to solve these two coupled ...
1
vote
2answers
73 views

What's phonon mean free path

This is probably a naive question but still. Phonons are quasiparticles that emerge when we quantize motion of a lattice. In this sense, they have no location in space, they are just energy quanta of ...
0
votes
0answers
33 views

Can measurement of Spontaneous Magnetization and susceptibility lead one to deduce the magnetic structure of a magnetic compound?

For a given magnetic compound, spontaneous magnetization and susceptibility are measured at various temperatures (in this paper). (SMS measurement) From neutron diffraction data the compound is found ...
0
votes
2answers
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 ...
9
votes
3answers
305 views

How to cut a stone on a White Dwarf?

I've heard that white dwarf stars are extremely dense and hard. So, if I had a piece of white dwarf matter, would it be possible to cut it (or otherwise) into a custom shape? How could one do that?
1
vote
0answers
57 views

Why is there a superconducting dome in superconductors?

Generally speaking, by the well-known BCS theory, the more carrier density( density of state at Fermi surface) leads to higher critical temperature. However, in many researches, people fond that the ...
21
votes
1answer
2k views

Emergent symmetries

As we know, spontaneous symmetry breaking(SSB) is a very important concept in physics. Loosely speaking, zero temprature SSB says that the Hamiltonian of a quantum system has some symmetry, but the ...
1
vote
1answer
111 views

How can I write the Anderson hamiltonian as a matrix? [closed]

How can I write this Hamiltonian: $$ H = \sum E_d \hat{n}_d + \sum_k \epsilon_k\hat{n}_k + \sum_k V_{kd} (\hat{a}^\dagger_k \hat{a}_d + \hat{a}^\dagger_d \hat{a}_k) $$ in matrix form using its ...
0
votes
0answers
40 views

Conductance measurement of InAs/GaSb Quantum Spin Hall Edges

My questions are related to recent article: http://arxiv.org/ftp/arxiv/papers/1507/1507.08362.pdf I can't figure out how their sample (wafers) actually looked like. In particular I can't understand ...
1
vote
0answers
22 views

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 ...
2
votes
1answer
108 views

Atomic physics - lattice energy

Question: Why is ionic lattice energy inversely proportional to the radius of the atom? Most heterogeneous covalent molecules are polar to some extent. The degree of polarity, or the dipole moment, ...
1
vote
1answer
30 views

Neutralizing Background and Fractional Quantum Hall ground state

The idealized many-body Hamiltonian describing FQH is given by $$ H = \sum_i \left\{\frac{[\vec{p}_i -e/c \vec{A}(\vec{r}_i)]^2}{2m}+V(\vec{r}_i)\right\} + \frac{1}{2}\sum_{i\neq j} ...
1
vote
0answers
63 views

Correspondence between variational method and Feynman diagrams

There are two ways to look at the Hartree or Hartree-Fock equations. One method relies on the variational method for a particular type of the probe function and the second one originates from ...
1
vote
1answer
42 views

Effective mass approximation Wannier function lattice vector operator approximate representation proof. Yu and Cardona

I am having difficulty in Yu and Cardona 4th edition chapter 4 page 164, equation 4.9 to 4.10 I just do not understand how to go from line 4.9 to 4.10. 4.9: $$ R_{op} \psi(\mathbf{r}) = ...
7
votes
1answer
634 views

To what extent can the superconducting order parameter be thought of as a macroscopic wavefunction?

I know that the order parameter does not obey the Schrodinger equation; it instead obeys the Ginzburg-Landau equation. However, I am unclear as to the situations under which the view of the ...
1
vote
1answer
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 ...
0
votes
1answer
57 views

Landau level for quadratic band touching in Dirac Hamiltonian

I wonder if there is anyone or any references that have solved the Landau level spectrum and eigenstates with respect to the following Hamiltonian: \begin{equation} ...
0
votes
0answers
35 views

Why is graphene “gate tunable”?

I am reading Geim and Novoselov's classic paper on electrostatic doping of graphene: http://arxiv.org/abs/cond-mat/0410550 Three parts to the same broad question: 1) I am looking for some rigorous ...
0
votes
1answer
31 views

What is the 'dimensionality' in solid state materials?

In the context of condensed matter physics, when it is referred to a '1D', '2D' or '3D' material, what context is this dimensionality understood in? Real space? momentum space? or something else? We ...
1
vote
1answer
42 views

Static structure function for non-interacting Fermi gas

I'm wondering how would one go on about to calculate the static structure function with the ground state being $|\phi_0\rangle$: $S_\vec{q}=\frac{1}{N}\langle ...
1
vote
0answers
49 views

Inuitive analogy for localization?

I'm looking for a plain English analogy for electron/wave localization. And in particular weak localization and Anderson/strong localization. Is it possible to describe these phenomena in simple terms ...
0
votes
1answer
33 views

Can magnetization measurement give dimensionless susceptibility without knowledge of volume and density of the material

In a magnetization measurement (as a function of temperature) experiment, M is measured in emu (1 emu = 1 erg/G). Weight of the sample used in the experiment is known. Without knowing the volume and ...
0
votes
2answers
101 views

Can mercury evaporate if it's covered by water?

I was recently watching a video about elemental mercury and how it's cleaned up in water (fish tanks), and it was mentioned how mercury can be toxic in vapor form. My question is, if I were to drop a ...
0
votes
0answers
37 views

Nuclear Cusp Condition

Suppose I write a Hamiltonian for an atom, it will contain electron-electron repulsion term and nucleus-electron attraction term. But, these terms will diverge, for example, position of an electron ...
1
vote
0answers
76 views

What makes a system topological?

As I understand, if the Chern number which is obtained by integrating Berry curvature over a surface with a boundary is an integer, then the Chern number is a topological invariant. So when does Chern ...
6
votes
3answers
2k views

Why can, or can not, a perfectly incompressible fluid exist?

Water is normally assumed to be an incompressible fluid - for example in the context of calculations involving water pressure. I wondered whether that is strictly true, or an approximation? Later I ...
1
vote
1answer
57 views

Hubbard model in the t>>U limit

I know one can obtain the t-J model from the Hubbard one by taking the limit $t\ll U$ in the following Hamiltonian: $H= -t\sum_{i\neq j}a_{i\sigma}^\dagger a_{j\sigma}+U\sum_i ...
1
vote
2answers
137 views

What can we learn from a band structure diagram?

Other than the band gap and its magnitude, what are the things that we can immediately learn about the properties of the material just by glancing at its band structure? Can we say something about ...
0
votes
1answer
77 views

Ground state of AKLT chain invariant under time-reversal?

The AKLT chain is an example of an SPT phase protected by time-reversal symmetry. The Hamiltonian of the system has time-reversal symmetry. The ground state wave function can be pictured as follows ...
1
vote
1answer
65 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?
16
votes
3answers
6k views

How does electricity propagate in a conductor?

On a systems level, I understand that as electrons are pushed into a wire, there is a net field and a net electron velocity. And I've read that the net electron drift is slow. But electricity ...
2
votes
1answer
130 views

Wannier functions on a ring

Let's say I have a single particle hamiltonian in a periodic potential, for example a 1D lattice such that: $$H = -\frac{\partial_x^2}{2m} + V(x) $$ with $ V(x+a) = V(x)$ where $a$ is the lattice ...
4
votes
2answers
175 views

Are critical exponents below and above the critical point always same?

The scaling relations don't distinguish the the critical exponents below and above the critical value. In the mean field level, I understand these critical exponents are same whatever one approaches ...
1
vote
0answers
60 views

String operator in the string-net model

The string operator is a way to study the quasiparticle excitations in the string-net model http://arxiv.org/abs/cond-mat/0404617. It is claimed in the above reference (Eq.(19), p.9) that for string ...
0
votes
0answers
60 views

Time Reversal Bulk Hamiltonian

This questions is from pages 68 and 69 of: http://fizipedia.bme.hu/images/1/14/Topological_insulators.pdf For a lattice, time reversal invariance of the bulk corresponds to the equation (Eqn 6.11): ...
2
votes
0answers
34 views

why are quantum vortices so large?

Quantum vortices in helium are almost macroscopic, and can be be imaged in a light microscope: http://www.aps.org/units/dfd/pressroom/papers/gaff09.cfm How can vorticity be quantized on such a large ...
1
vote
0answers
46 views

Hamiltonian in Majorana basis

I read (for example here: cond-mat/0010440) very often that if we transform the Hamiltonian from a fermionic basis to the basis of Majorana operators by expanding the fermionic operators in real and ...
1
vote
0answers
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?