Tagged Questions

2
votes
0answers
96 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), ...
5
votes
1answer
153 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 ...
9
votes
1answer
192 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 ...
4
votes
1answer
119 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
votes
1answer
149 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 ...
6
votes
1answer
300 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 ...
3
votes
1answer
166 views

How to measure Projective Symmetry Group in spin liuquid?

Quasiparticles in spin liquid will no longer be the representation of symmetry group. So when group elements act on quasiparticles, there will be some phase factor. For example, in $\pi$ flux state, ...
4
votes
0answers
130 views

What is the mass of the emergent magnetic monopoles in spin ice and how is the mass of an emergent particle determined?

In solid state physics emergent particles are very common. How one determines if they are gap-less excitations? Do the defects in spin ice called magnetic monopoles have mass? What is the mass of ...
2
votes
0answers
187 views

condensed matter physics must reads [closed]

Possible duplicate: Books for Condensed Matter Physics I'm looking to learn more about cutting edge research in condensed matter theory. I hope you'll help me find some recommended articles in ...
6
votes
1answer
156 views

Spin-ice materials with strong quantum fluctuations

Spin-ice materials are insulating materials where spins form a 3D pyrochlore lattice and have a frustrated magnetic interaction. The spin dynamics in most spin-ice materials is very classical and has ...
7
votes
1answer
565 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
votes
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 ...
7
votes
2answers
452 views

Majorana zero mode in quantum field theory

Recently, Majorana zero mode becomes very hot in condensed matter physics. I remember there was a lot of study of fermion zero mode in quantum field theory, where advanced math, such as index ...
17
votes
10answers
1k views

What is spontaneous symmetry breaking in QUANTUM systems?

Most descriptions of spontaneous symmetry breaking, even for spontaneous symmetry breaking in quantum systems, actually only give a classical picture. According to the classical picture, spontaneous ...
4
votes
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 ...
5
votes
1answer
270 views

Graphene Moebius Strip

I'm refering to the Paper: PHYSICAL REVIEW B 80, 195310 (2009) "Möbius graphene strip as a topological insulator" Z. L. Guo, Z. R. Gong, H. Dong, and C. P. Sun. The paper is also available as a ...
15
votes
3answers
891 views

Are elementary particles actually more elementary than quasiparticles?

Quarks and leptons are considered elementary particles, while phonons, holes, and solitons are quasiparticles. In light of emergent phenomena, such as fractionally charged particles in fractional ...
8
votes
1answer
305 views

Kramer's-Kronig relations for the electron Self-Energy Σ

I'm currently studying an article by Maslov, in particular the first section about higher corrections to Fermi-liquid behavior of interacting electron systems. Unfortunately, I've hit a snag when ...
6
votes
1answer
159 views

Thermodynamic limit “vs” the method of steepest descent

Let me use this lecture note as the reference. I would like to know how in the above the expression (14) was obtained from expression (12). In some sense it makes intuitive sense but I would ...
4
votes
1answer
75 views

Derivatives of fluctuations about a condensate

Firstly I am not sure as to whether I am using the word "condensate" in the right context. In QFT contexts I think I see it getting used to mean the space-time independent solution which would solve ...
4
votes
1answer
324 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 ...
11
votes
2answers
131 views

Literature on fractal properties of quasicrystals

At the seminar where the talk was about quasicrystals, I mentioned that some results on their properties remind the fractals. The person who gave the talk was not too fluent in a rigor mathematics ...
7
votes
1answer
49 views

Canonical averages in a Fermi gas aka generalized Fermi-Dirac distribution

I am in the process of applying Beenakker's tunneling master equation theory of quantum dots (with some generalizations) to some problems of non-adiabatic charge pumping. As a part of this work I ...
21
votes
2answers
165 views

Renormalization Group for non-equilibrium

For equilibrium/ground state systems, a (Wilson) renormalization group transformation produces a series of systems (flow of Hamiltonians/couplings $H_{\Lambda}$ where $\Lambda$ is the cut-off) such ...
18
votes
1answer
780 views

How Fundamental is Spin-Orbit Coupling to Topological Insulators?

I'm well aware this is a very active area of research so the best answer one can give to this question may be incomplete. Topological states in condensed matter are well-known, even if not always ...
11
votes
1answer
51 views

Limitations in using FLEX as a DMFT solver

When using the fluctuating exchange approximation (FLEX) as a dynamical mean field theory (DMFT) solver, Kotliar, et al. (p. 898) suggest that it is only reliable for when the interaction strength, ...
11
votes
5answers
2k views

What does it mean for a Hamiltonian to be gapped?

I've read some papers recently that talk about gapped Hamiltonians or gapless systems, but what does it mean? Edit: Is an XX spin chain in a magnetic field gapped? Why or why not?
15
votes
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
votes
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 ...
12
votes
4answers
2k views

A pedestrian explanation of conformal blocks

I would be very happy if someone could take a stab at conveying what conformal blocks are and how they are used in conformal field theory (CFT). I'm finally getting the glimmerings of understanding ...