Zoltán Tajkov
PhD Student
Department of Biological Physics, Eötvös Loránd University
BME Elméleti Fizika Szeminárium,
22. November, 2019.
A. K. Geim, I. V. Grigorieva Nature 499, 419 (2013)
Ishizaka et al. Nature Materials 10, 521 (2011)
Fülöp et al. 2D Mater. 5, 031013 (2018)
BiTeI sandwich: Kou et al. ACS Nano, 8 10448 (2014)
trivial
topological
Z. Tajkov et al. Nanoscale 11, 12704 (2019)
Weiss et al. Advanced Materials, 24 5782(2012)
Z. Tajkov et al. Appl. Sci. 9, 4330 (2019)
BiTeBr
BiTeCl
BiTeI
BiTeI is different, why?
Z. Tajkov et al. Appl. Sci. 9, 4330 (2019)
BiTeCl / BiTeBr, graphene
BiTeI, graphene
\(E_\mathrm{F} \) for graphene
\(E_\mathrm{F} \) for BiTeX
WF are different!
topological
trivial
Z. Tajkov et al. Nanoscale 11, 12704 (2019)
The most important parameters
Kekulé
Kane-Mele
Strain promotes SOC \( \rightarrow \) TI
We have to deal with:
Divide et impera
Start with graphene + strain
Tight-binding model for pristine graphene
In real space:
Consider the Kekulé pattern as an ordered disorder
Kekulé perturbation operator
The periodicity is different!
In real space:
Kene-Male perturbation operator
The periodicity is different!
In real space:
The full tight-binding Hamiltonian:
Dispersion relation \( \rightarrow \) Fourier-transformation
Fourier-transformation is tricky...
After the FT
\( \boldsymbol{\Omega} \) and \( \boldsymbol{\Gamma} \) are ugly \( 3\times3 \) matrices.
Identify low-energy part:
Taylor expansion, momentum and strain are the small parameters
The low-energy Hamiltonian
Strain can close the gap at \(\boldsymbol{k}=\boldsymbol{0}\) if
Gamayun et al. New J. Phys. 20, 023016 (2018)
Andrade et al. Phys. Rev. B 99, 035411 (2019)
László Oroszlány
János Koltai
József Cserti
Z. Tajkov et al. Nanoscale 11, 12704 (2019)
Z. Tajkov et al. Appl. Sci. 9, 4330 (2019)