The study of physical properties condensed phases of matter, including solids and liquids.
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Why is planar geometry preferred to observe ordinary Hall effect?
In the Physics Today article by Avron et.al. "A Topological Look at the Quantum Hall Effect" Physics Today (2003) it is suggested that to observe ordinary Hall effect, planar geometry is preferred to ...
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39 views
Some questions about the edge states for time-reversal invariant topological superconductors?
Stimulated by my some recent calculations on edge states(ES) for time-reversal invariant(TRI) topological superconductors(TS) as well as many questions concerning the "edge states" in Physics ...
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51 views
Why do some things break when twisted?
Explain at the atomic level why twisting something, like a thin tree branch or arm, will break from twisting, but something else, such as a bowling ball or cinder block, will not break from twisting.
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17 views
Kinetic and Thermodynamic Dopant Solubility
I've read that both the "kinetic" and "thermodynamic" solubility of impurities limit substitutional dopant concentrations. Unfortunately, I haven't found a clear explanation of the two types and the ...
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1answer
61 views
NP-completeness of non-planar Ising model versus polynomial time eigenvalue algorithms
From the papers by Barahona and Istrail I understand that a combinatorial approach is followed to prove the NP-completeness of non-planar Ising models. Basic idea is non-planarity here. On the other ...
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1answer
24 views
Origin of interaction in inelastic neutron scatting
In solid state physics, inelastic neutron scattering is a commonly-used experimental technique for probing the energy spectrum of phonon and magnon excitations. This technique relies on the ...
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2answers
80 views
Currents and the Speed of Light
Why is it that currents don't flow at the speed of light, but rather significant ratios of the speed of light.
I don't have any formal reasoning as to why they would flow at the speed of light-I just ...
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1answer
87 views
A corollary of Mermin-Wagner Theorem
The picture above shows Mermin-Wagner Theorem and its corollary. How can the corollary be derived from Mermin-Wagner Theorem?
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67 views
Fermi level for the bulk of topological insulator
"Fermi level" is the term used to describe the top of the collection of electron energy levels at absolute zero temperature. Why does the Fermi level for the bulk of topological insulator fall within ...
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3answers
136 views
Why is the Coulomb potential in pseudo-2D experiments proportional to the logarithm of distance?
Inspired by this question, I ask another. Theoretically, Coulomb potential in 2D is proportional to the logarithm of distance; In experiments, though electrons are constrained in a pseudo-2D ...
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163 views
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Ferromagnetism with mobile spins
How can electron spins in Iron at room temperature have ferromagnetic order even though they are travelling at very high speeds?
One could argue that spin and motion are completely uncorrelated and ...
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1answer
84 views
$SU(N)$ Neel manifold
I have seen multiple papers talking about the manifold, $M$ of the Neel order for an $SU(N)$ magnet is
$$M~=~\frac{U(N)}{U(m)\times U(N-m)}.$$
So for instance, a $SU(2)$ magnet has manifold
$$M ~=~ ...
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21 views
What's the real value of screening length?
I know that the screening length (R) is an effective distance over which the nucleus of an atom is active, since it is screened by the orbiting electrons.Various derivations for R have been proposed, ...
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30 views
How to understand topological order at finite temperature?
I have heard that in 2+1D, there are no topological order in finite temperature. Topological entanglement entropy $\gamma$ is zero except in zero temperature. However, we still observe some features ...
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44 views
Why doublons and holons are not bounded in spin-1/2 Hubbard chain?
The Hubbard model reads
$$H = -t \sum_{\langle ij \rangle, \sigma} c_{j\sigma}^\dagger c_{i\sigma} + U\sum_i n_{i\uparrow}n_{i\downarrow} $$
In the large $U$ limit and at half-filling, the Hubbard ...
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56 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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1answer
36 views
If my lattice has an atomic basis, do I also find the reciprocals of the basis vectors to get the reciprocal crystal structure?
That is what my crystal structure looks like. The blue atoms sit on every lattice point (basis vector of $\{0,0\}$) and the red atoms have basis vector of $\left\{{2\over3},{1\over3}\right\}$. The ...
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28 views
Is there a critical order of the Abelian gauge theory in (2+1)D
In (2+1)D spacetime, it is known that the $U(1)$ gauge theory is always confined (according to Polyakov), while the $\mathbb{Z}_2$ gauge theory can support a deconfined phase. Now consider a generic ...
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1answer
41 views
Is this 2D structure triclinic?
The only rotation axis obvious to me is rotation by 360 degrees, the identity. Vertical mirror planes I've been dicing and cutting it through several planes and I still see none. Yet, the structure ...
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1answer
68 views
What is the interface tension between ordered and disordered phases of the Potts model?
I read in these papers(1,2) the concept of interface tension. I can't understand its definition. I can hardly imagine there is some tension in a model. Any help will be appreciated.
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47 views
What is tricritical point？
Critical point is the transition temperature of a second order phase transition. But what does tricritical point mean? WIki says that a tricritical point is a point in the phase diagram of a system at ...
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1answer
41 views
What would be the basis vectors for this 2D crystal structure?
In the above image, I have a 2D crystal structure. The lattice vectors are described by:
a = {-1/2, -Sqrt[3]/2};
b = {1, 0};
and the location of atoms A and B ...
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3answers
98 views
What is the difference between lattice vectors and basis vectors?
Google has not been very useful in this regard. It seems no one has clearly defined terms and Kittel has too little on this.
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1answer
96 views
How to understand the emergent special relativity in the superfluid?
The superfluid vacuum theory was proposed to understand some features of the vacuum (aether) from the emergence point of view. Although made up of non-relativistic atoms, the low-energy excitations of ...
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1answer
39 views
Dopant concentration and changes in band gap energy
Thanks to this lovely website, I was able to pop out reasonable values for my band gap energies from a translucent material. As expected, I found a decrease in band gap energy due to my treatments.
...
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59 views
A general wavefunction in a square lattice
Suppose we have a square lattice with periodic condition in both $x$ and $y$ direction with four atoms per unit cell, the configuration of the four atoms has $C_4$ symmetry. What will be a general ...
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26 views
Wavefunction in first Brillouin zone
We know that with symmetry, Brillouin zone is nothing but copies of its irreducible zone, so can we conclude that we can find all possible wavefunctions in its irreducible zone? What about ...
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1answer
65 views
What is the importance of the Fermi energy $E_F$ or the chem. potential $\mu$ for topological superconductors
A lot of effort is put into shifting the Fermi energy of a topological insulator to exactly zero which then provides some advantages when this TI is coupled with a superconductor.
I don't understand ...
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1answer
116 views
What're the relations and differences between slave-fermion and slave-boson formalism?
As we know, in condensed matter theory, especially in dealing with strongly correlated systems, physicists have constructed various "peculiar" slave-fermion and slave-boson theories. For example,
For ...
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49 views
How to understand Modular transformation in topological order?
Topological order in (2+1)D is described by its ground state degeneracy and the braiding statistics and topological spins of excitations. People believe that these information is all encoded in ground ...
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41 views
Lambda transition data points of $\require{mhchem}\ce{^4He}$
I'm looking to get some data on the lambda transition of $\require{mhchem}\ce{^4He}$. I need the data points of the specific heat vs. temperature graph, if that makes sense.
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49 views
Is it possible to have topological degeneracy in 1D ?
I mean to have q-fold degenerate ground states on a ring which could not be lifted by local perturbation.
If the answer is no, then what is the physical (or mathematical) reason against having such ...
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1answer
42 views
If a balloon is continuously filled with air and stays at a constant shape and size will there be any empty space in the balloon?
If a container like a balloon but with constant volume is filled, is it possible to pack air molecules so closely together that they don't have any empty space between them? If so, what would this ...
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1answer
29 views
Difference between Wigner crystal state and fractional quantum Hall (FQH) state
Wigner crystal and FQH effect are both due to strong electron-electron interaction under magnetic field. As we know, Landau's symmetry-breaking cannot be used to describe FQH state. But can it be used ...
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94 views
How to define the mirror symmetry operator for Kane-Mele model?
Let us take the famous Kane-Mele(KM) model(http://prl.aps.org/abstract/PRL/v95/i22/e226801 and http://prl.aps.org/abstract/PRL/v95/i14/e146802) as our starting point.
Due to the time-reversal(TR), ...
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102 views
When can a body of water glow in space?
How would superionic water be formed at the core of a giant water planet? The publication
Giant planets may host superionic water, E. Marris, Nature News, 22 March 2005,
states that water in ...
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23 views
What are some applications of crystal fabrication? [closed]
I have heard of some applications here or there in certain papers, but I am looking for a broader scope of examples.
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2answers
133 views
Would HgTe be a topological insulator?
In "Quantum Spin Hall Insulator State in HgTe Quantum Wells", researchers observed a 2D topological insulator by sandwiching HgTe between CdTe. Is the CdTe really necessary? Would Vacuum/HgTe/Vacuum ...
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107 views
Some questions about anyons?
(1) As we know, we have theories of second quantization for both bosons and fermions. That is, let $W_N$ be the $N$ identical particle Hilbert space of bosons or fermions, then the "many particle" ...
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72 views
Simple uncertaintly calculation of the center coordinates of a Landau Level
I am reading the following review paper on the Quantum Hall Effect. I am sorry for the extremely stupid question, but I have been stuck on this very easy equation for long.
In equation 2.39, the ...
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1answer
58 views
Calculation of the quantized Hall coefficient in the Integral Quantum Hall Effect
I have been reading about the QHE over the past couple of days. I am facing difficulty understanding a calculation in this review.
www.nimt.or.th/nimt/upload/linkfile/sys-metrology-248-434.pdf
In ...
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1answer
115 views
What is Anderson localization? Could someone give an example worked out in detail?
What is Anderson localization, for someone with no previous knowledge on the subject?
I tried to read Anderson's original paper, but it was too terse for me. I have seen a couple of intuitive ...
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29 views
Neutron scattering for a critical magnetic-ordering system : what about critical opalescence?
Liquid-gas transition critical point is believed to share the same universality class as the 3D Ising model.
We know that the liquid-gas transition is characterized by a phenomenon called critical ...
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1answer
41 views
Influence of the temperature on the ionization energies for impurities in silicon
Is there any dependence of the impurities ionization energy on temperature in silicon? I mean if there are any interactions between localized electron and phonons which leads to renormalization of ...
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2answers
394 views
What is the mathematical reason for topological edge states?
There are many free fermion systems that possess topological edge/boundary states. Examples include quantum Hall insulators and topological insulators. No matter chiral or non-chiral, 2D or 3D, ...
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3answers
142 views
What is the mathematical justification for the quadratic approximation to the energy of a spring in a one-dimensional lattice?
It follows easily from this draw, the length $l$ of this spring as a function of the vertical distance $x$, as $l(x)=\sqrt{1+x^{2}}$
Now, $l$ can be expressed as a MacLaurin expansion:
$$l(x) = ...
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2answers
38 views
Free spin (Curie) Paramagnetism
I'm working through a derivation for Curie paramagnetism and hope someone could help clarify a couple of steps. The way that makes sense to me (although now I have seen the wikipedia derivation below ...
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1answer
76 views
Electrical energy storage in superconductors
I am a first year A-level student and I am doing a project about the possibility of storing electrical energy in a superconductor. I have researched and I am aware of the critical current density and ...
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2answers
135 views
Graphene +1 extra carbon bond
I'm not a physicist just a curious mind, so please go easy!
I was just watching a BBC Horizon Documentary that featured a piece on the recently discovered material Graphene. One of the facts ...
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1answer
148 views
A question on the doped Kitaev-Heisenberg model?
Recently, some groups have studied the effects of doping the Kitaev model on honeycomb lattice(e.g.,http://arxiv.org/abs/1109.6681 and http://arxiv.org/abs/1109.4155) and their calculations show the ...
