Questions tagged [topological-phase]

It regroups the notion of Berry's phase, Aharonov-Bohm and Aharonov-Casher type of phase among others. It is mathematically described by the notion of the (an-)holonomy group, associated to the vast mathematical notion of connection on a finer-bundle.

The use of topological phase arises in almost all the areas of modern physics, ranging from continuous mechanics (elastic problems, ...) eventually described by statistical physics methods (fluid mechanics, polymer physics, ...) to high-energy physics passing through the quantum-side of condensed matter (defects in ordered media, fluxoid quantisation, two-dimensional problems, quantisation of Hall conductance ...) and mesoscopic problems (adiabatic pumping, proximity effect, ...)

It should be not confounded with the notion of topological order (i.e. the word phase has to be understood as the phase of the wave-function, not as any kind of phase of matter like in the term phase transition which a topological phase actually doesn't have). The appearance of a topological phase is a (necessary, not sufficient) prerequisite for the appearance of topological order.

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Local explanation of the Aharonov-Bohm effect in terms of force fields

Here is an interesting paper for the Physics SE community: On the role of potentials in the Aharonov-Bohm effect. Lev Vaidman. Phys. Rev. A 86 no. 4, 040101 (R) (2012). arXiv:1110.6169 [quant-ph]. You should check it out because it's an amusing…
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What does the Chern number physically represent?

In 2D the Chern number can be written as $$C_m=\frac 1{2\pi}\int_{BZ}\Omega_m(\mathbf k)\cdot d^2 \mathbf k$$ where we are integrating over the Brillouin zone. In 2D this is equivalent to finding the "flux" of the Berry curvature through the entire…
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Chern insulator vs topological insulator

What is the basic distinction between a Chern Insulator and a Topological Insulator? Right now I know that a Chern Insulator has "topologically non-trivial band structure" and that a Topological Insulator has "symmetry protected surface states".
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What is so topological about topological phase transitions?

I am studying the KT-transition, which is called a topological phase transition. The phase transition is driven by vortices in a 2-D superfluid, where it is shown that at a critical temperature $T_c$ free vortices are energetically favoured over…
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What is the relation between non-local order parameters and topological phases?

I know of several definitions of phases of matter: The first is the "old" one, Landau theory and symmetry breaking. In this definition we pick a local order parameter $m$ (as far as I can tell this is quite vaguely defined). If the state had the…
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Are there topological non-trivial states in zero dimension?

The periodic table of topological insulators and superconductors suggests that there can be topological non-trivial phases in zero dimension in non-interacting system with certain symmetries. A 0D system can be thought as a single atom, a quantum…
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Why do lattice models of fermions need a spin structure?

It is well-known that in order to define a relavistic quantum-field theory containing fermions on a general manifold $M$, the manifold $M$ needs to be equipped with a spin structure. The spin structure is a lift of the frame bundle (which is a…
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Why is the phase picked up during identical particle exchange a topological invariant?

I've been wondering about the standard argument that the only possible identical particles in three dimensions are bosons or fermions. The argument goes like this: Consider exchanging the positions of two identical particles in 3D. Because the…
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What is the topological space in “topological materials/phases of matter”?

I’m embarrassed to admit that after sitting in on several “topological physics” seminars, I still don’t understand the basic ideas of the area. In particular, when physicists talk about the “topology” and “topological properties” of a system, what…
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Small confusion about the Aharonov-Bohm effect

I am mostly aware of the Aharonov-Bohm effect's (AB effect) physical interpretation, as well as the corresponding mathematical/differential geometric interpretation. What does confuse me slightly however is the physical part of the derivation…
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1+1d TSC as $Z_2^f $ symmetry breaking topological order?

I have been struggling recently with a comprehensive problem on the relationship between topological superconductor and topological order. My question originates from reading a work conducted by Prof. Wen http://arxiv.org/abs/1412.5985 ,also a…
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Definition of short range entanglement

When studying Symmetry Protected Topological phases, one needs to define what a short range entangled (SRE) states means. But there appears to be different definitions that are not equivalent to each other. In http://arxiv.org/abs/1106.4772,…
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Does the Kosterlitz–Thouless transition connect phases with different topological quantum numbers?

The Kosterlitz-Thouless transition is often described as a "topological phase transition." I understand why it isn't a conventional Landau-symmetry-breaking phase transition: there is no local symmetry-breaking order parameter on either side of the…
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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. This is the case for integer and some fractional…
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Has The Aharonov-Bohm Effect Been Experimentally Proven?

I have encountered two contradicting papers on the Aharonov-Bohm Effect: One supporting, The Aharonov-Bohm Effects: Variations on a Subtle Theme. H Batelaan and A Tonomura. Physics Today 62 pp. 38-43 (2009). doi:10.1063/1.3226854,…
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