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SUMMARY:Characterizing a two-dimensional high-order topological insulator
DTSTART;VALUE=DATE-TIME:20201029T093000Z
DTEND;VALUE=DATE-TIME:20201029T095000Z
DTSTAMP;VALUE=DATE-TIME:20220519T114500Z
UID:indico-contribution-6389@indico.nikhef.nl
DESCRIPTION:Speakers: João Martins\n\nA two-dimensional topological insul
ator presents gapless topologically protected edge states and there is a c
orrespondence between the topological invariant and the number of edge-sta
tes\, known as the bulk-boundary correspondence. Recently proposed higher-
order topological insulators (HOTIs) generalize the bulk-boundary corresp
ondence and present topological states with dimensions two or more lower t
han that of the bulk. Two-dimensional HOTIs\, for instance\, present topol
ogically protected corner states. The main goal of this work was to study
numerically a variation of a 2D Su-Schrieffer-Heeger (SSH) tight-binding m
odel in order to characterize the topologically protected corner states.\n
As a first example\, a numerical study of the one-dimensional SSH chain wi
ll be presented. The electron hopping ratio is studied and identified as a
parameter for a topological phase transition\, by calculating the density
of states (DOS) of the SSH chain with different hopping energies.\nSecond
ly\, a 2D SSH model was analyzed\, where the band structure and the local
density of states (LDOS) were studied. Square and ribbon geometries were s
tudied in order to observe different topological phases.\nThirdly\, and la
stly\, a modified 2D SSH model was studied\, where a quadrupolar to trivia
l topological phase transition is clearly observed. Holes of different geo
metries (square and cross holes) were created in a square lattice. The eff
ect of the holes’ presence in the lattice\, regarding its band structure
and LDOS\, was shown to change the behavior of the topological phase tran
sitions. A quadrupolar topological phase transition was observed in an inf
inite periodical square super-lattice with a cross hole geometry. This res
ult can be of interesting applications\, e.g.\, in photonics\, to mediate
energy transfer in photonic crystals.\n\nhttps://indico.nikhef.nl/event/27
20/contributions/6389/
LOCATION:Zoom Link: https://videoconf-colibri.zoom.us/j/81437260131?pwd=d
2V4RExtV05sazg5dnNhYUJORGVnUT09 (Web-based event - Lisbon - Porto - Braga
)
RELATED-TO:indico-event-2720@indico.nikhef.nl
URL:https://indico.nikhef.nl/event/2720/contributions/6389/
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