Floquet engineering of topological phase transitions in a quantum spin Hall <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mrow> <mml:mi>α</mml:mi> <mml:mtext>−</mml:mtext> <mml:msub> <mml:mi>T</mml:mi> <mml:mn>3</mml:mn> </mml:msub> </mml:mrow> </mml:math> system
Kok Wai Lee, Mateo Jalen Andrew Calderon, Xiang‐Long Yu, Ching Hua Lee, Yee Sin Ang, Pei-Hao Fu
Abstract
Floquet engineering of topological phase transitions driven by a high-frequency time-periodic field is a promising approach to realizing new topological phases of matter distinct from static states. Here, we theoretically investigate Floquet engineering topological phase transitions in the quantum spin Hall $\ensuremath{\alpha}\text{\ensuremath{-}}{T}_{3}$ system driven by an off-resonant circularly polarized light. In addition to the quantum spin (anomalous) Hall insulator phase with multiple helical (chiral) edge states, spin-polarized topological metallic phases are observed, where the bulk topological band gap of one spin subband overlaps with the other gapless spin subband. Moreover, with a staggered potential, the topological invariants of the system depend on whether the middle band is occupied because of the breaking of symmetry with respect to the center of energy-momentum plane. Our work highlights the significance of Floquet engineering in realizing new topological phases in $\ensuremath{\alpha}\text{\ensuremath{-}}{T}_{3}$ lattices.