Tagged Questions
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0answers
32 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 ...
4
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0answers
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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0answers
52 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 ...
6
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0answers
119 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" ...
5
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1answer
156 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 ...
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1answer
193 views
What is the “BCS Cooper pair condensation” as a physical phenomenon in terms of experiments?
"Thought" experiments and "numerical" experiments are allowed.
This question is motivated by the question Has BCS Cooper pair condensate been observed in experiment? ,
and by our recent research on ...
10
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2answers
488 views
Basic questions in Majorana fermions
Why any fermion can be written as a combination of two Majorana fermions? Is there any physical meaning in it? Why Majorana fermion can be used for topological quantum computation?
4
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1answer
183 views
Chiral edge state as topological properity of bulk state
As far as I know, quantum hall effect and quantum spin hall effect has chiral edge state. Chiral edge state is usually closely related with delocalization, since back scattering is forbidden. However, ...
10
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2answers
353 views
Why quantum hall effect has chiral edge state?
The most popular explaination may be the following: in magnetic field, electrons move in cycolotron orbits, such cycolotron orbits ensure electrons to move in one direction at the edge. That is why ...
4
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1answer
120 views
Notation in Spin Liquid
When construct spin liquid by projective symmetry group, we can classified spin liquids by the invariant group (IGG) of their mean field ansatze. For example, we can have Z2, U(1) and SU(2) spin ...
6
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1answer
150 views
Chiral coupling in string-nets
In Xiao-Gang Wen's review of topological order http://arxiv.org/abs/1210.1281 , he states in footnote 52 that string-nets are so far unable to produce the chiral coupling between the SU(2) gauge boson ...
3
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1answer
103 views
Measurement of topological spin
How do you measure the topological spin of an anyon? So how could an experimental setup look like? Is topological spin an observable at all?
6
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1answer
110 views
String-net condensation in 3D
In 2D and 3D quibit models, string-net condensation can happen. In 3D or higher models, is it possible for surfaces (instead of just strings) to condense?
5
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2answers
443 views
Why are Topological Superconductors hard to make?
Topological insulators (TI) have already been made in lab. Topological superconductors (TSC), being close cousins of TI, seem harder to make.
Why is that?
It seems that materials in connection with ...
6
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1answer
301 views
Realization of Witten-type topological quantum field theory in condensed matter physics
It is well-known that some exotic phases in condensed matter physics are described by Schwarz-type TQFTs, such as Chern-Simons theory of quantum Hall states. My question is whether there are condensed ...
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1answer
159 views
$Z_2 $ topological index in spin liquid
What is $Z_2 $ topological index in spin liquid system? How to understand its physical picture in condensed matter?
7
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1answer
287 views
What is topological degeneracy in condensed matter physics?
What is topological degeneracy in strongly correlated systems such as FQH?
What is the difference between topological degeneracy and ordinary degeneracy?
Why is topological degeneracy important for ...
5
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1answer
329 views
Topological Order and Entanglement
I have a question about entanglement in condensed matter physics. It seems that topological order origins from long range entanglement, but what is long range entanglement? It is the same as long ...
7
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1answer
568 views
Is resonating valence bond (RVB) states long-range entangled?
Quantum liquid is at the core of condensed matter theory study, examples include superfluid in Bose Hubbard model, quantum spin liquid around the RK point of a quantum dimer model, string-net ...
5
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0answers
169 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 ...
4
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1answer
587 views
What is the relationship between string net theory and string / M-theory?
I've just learned from this one of Prof. Wen's answers that there exists a theory called string net theory. Since I've never heard about this before it picks my curiosity, so I`d like to ask some ...
4
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1answer
325 views
A physical understanding of fractionalization
all! Is there a physical understanding of fractionalization in condensed matter physics? The textbook approach is theoretical, not physical. I'm thinking of spin-charge separation for electrons, the ...
13
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4answers
1k views
Quantum Hall effect for dummies
In the past few days I've become increasingly intrigued by the QHE, mainly thanks to very interesting questions and answers that have appeared here. Unfortunately, I am as of yet very confused by all ...
15
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5answers
1k views
Simple models that exhibit topological phase transitions
There are a number of physical systems with phases described by topologically protected invariants (fractional quantum Hall, topological insulators) but what are the simplest mathematical models that ...
12
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2answers
1k views
What is a resonating valence bond (RVB) state?
There's something known as a "resonating valence bond" (RVB) state, which plays a role in at least some attempts to understand physics of high-$T_c$ superconductors. This, roughly, involves a state ...
