7 papers
Genus-protected higher-order topological phases
Shahroze Shahab, Hui Liu, Daniel Varjas +1
Higher-order topological phases (HOTPs) feature protected gapless modes on boundaries of higher codimension, such as the corners or hinges of a crystal. They are understood as bein…
The geometry of the Hermitian matrix space and the Schrieffer--Wolff transformation
GergŠPintér, György Frank, Dániel Varjas +1
In quantum mechanics, the Schrieffer--Wolff (SW) transformation (also called quasi-degenerate perturbation theory) is known as an approximative method to reduce the dimension of th…
AKLT Hamiltonian from Hubbard tripods
Claire Benjamin, Dániel Varjas, Gábor Széchenyi +2
We investigate how the spin-1 Affleck-Kennedy-Lieb-Tasaki (AKLT) Hamiltonian can emerge from a microscopic fermionic model based on half-filled Hubbard tripods. We first show that…
Fermi surface and topology of multiband superconductor BeAu
Riccardo Vocaturo, Klaus Koepernik, Dániel Varjas +3
The chiral material BeAu was recently identified as a multiband type-I superconductor with a critical temperature of 3.2 K. As a member of the B20 crystal family (space group $P2_1…
Effective Hamiltonians for Ge/Si core/shell nanowires from higher order perturbation theory
Sebastian Miles, A. Mert Bozkurt, Dániel Varjas +1
We theoretically explore the electronic structure of holes in cylindrical Germanium/Silicon core/shell nanowires using a perturbation theory approach. The approach yields a set of…
Non-unitary Time Evolution via the Chebyshev Expansion Method
Ãron Holló, Dániel Varjas, Cosma Fulga +2
The Chebyshev expansion method is a well-established technique for computing the time evolution of quantum states, particularly in Hermitian systems with a bounded spectrum. Here,…