All Questions
12
questions
1
vote
1
answer
113
views
What is the Haldane gap?
The Haldane Phase is a topological phase of matter in which a Haldane gap opens due to the breaking of either time-reversal symmetry or inversion symmetry. Physically speaking, what is the "...
- 43
3
votes
0
answers
131
views
Berry phase from Bloch wave functions in the basis of Wannier functions
The formulate to calculate berry phase for Bloch wave functions is
$$
\gamma = i \sum_{n\in occ}\int_{\mathcal{C}} dk \langle \psi_k^n|\partial_k|\psi_k^n\rangle,
$$
where $|\psi_k^n\rangle$ is a ...
- 337
1
vote
1
answer
84
views
Why number of left-moving and right-moving edge states on a finite lattice system is equal?
I read an arguments about number of left-movers and right-mover in finite system in paper titled as
Antichiral Edge States in a Modified Haldane Nanoribbon. In second paragraph of introduction, it ...
- 337
1
vote
0
answers
32
views
Phase freedom of the edge states in topological insulator
Suppose that we consider the BHZ-like Hamiltonian of the form
$$
H_{bulk}=\left(M-B k^{2}\right) \tau_{z}-A k_{x} \tau_{y}+A k_{y} \sigma_{z} \otimes \tau_{x}
$$
where $\tau_i $ acts on the orbital ...
- 503
1
vote
2
answers
377
views
Topological phases of matter
So according to this, scientists have discovered more than 5 states of matter we usually had that is the solid, liquid, gases, and Bose-Einstein-Condensate, and plasma. So how many topological phases ...
- 11
1
vote
1
answer
466
views
Argument for number of edge states as topological invariant for SSH model
I am currently reading the book "A short introduction to Topological insulators" by Asboth etal.
In the first chapter on SSH model, they argue (see sec 1.5.3) that number of edge states is a ...
- 43
1
vote
1
answer
259
views
Chern number for nonintracing hamiltonian while bands crossing
Is it possible to define and calculate chern number for two bands while they're crossing each other?
- 13
2
votes
0
answers
141
views
Does flat band imply localization?
Consider the Kitaev chain, whose Hamiltonian is as follows:
$$ H = -\mu \sum_n c_n^\dagger c_n -t\sum_n (c_n^\dagger c_{n+1} + \mathrm{h.c.}) +\Delta \sum_n (c_n c_{n+1} + \mathrm{h.c.}) $$
I have ...
- 171
2
votes
0
answers
339
views
About symmetry constraints in momentum space
When people study symmetry protected topological phases, certain symmetry constraints are enforced on the Hamiltonian. Specifically, for non-interacting fermionic systems, we could focus on the ...
- 171
0
votes
1
answer
321
views
Meaning of complex pairing terms in Kitaev chain
I am studying some properties of the one dimensional Kitaev chain, which has the following form:
$ H = -\mu \sum_n c_n^\dagger c_n - t \sum_n (c_{n+1}^\dagger c_n + h.c.) + \Delta \sum_n (c_n c_{n+1} ...
- 171
3
votes
1
answer
1k
views
The surface states and Fermi arcs in Weyl semimetals
I'm confused about surface states in Weyl semimetals. Assume that we have a single pair of Weyl points and the Fermi level turned to this points. In this https://arxiv.org/abs/1301.0330 paper the ...
- 341
1
vote
1
answer
198
views
Do topological transitions only occur at Dirac points?
Topological phase transitions happen when the band gap closes. It is not true that all band crossings are topological.
There are Dirac (linear) band crossings, quadratic band crossings, Dirac-like ...
- 351