Kavli Affiliate: Jing Wang
| First 5 Authors: Wen-Hao Bian, Wen-Hao Bian, , ,
| Summary:
We systematically investigate how static symmetry-breaking perturbations and
dynamic Floquet terms via a polarized light manipulate the topological phase
transitions in the two-dimensional quadratic-band-crossing-point (QBCP)
materials. The Berry curvature shows distinct behavior in such two situations.
It is linearly and quadratically proportional to the product of microstructural
parameters $t_x,z$ for the former and the latter, respectively. The static
perturbation eliminates the QBCP and opens an energy gap, which leads to the
momentum-inversion symmetry of Berry curvature. This yields a nontrivial Chern
number determined by the microstructural parameters. In contrast, we
demonstrate that either a circularly or an elliptically polarized light breaks
the time-reversal symmetry, transforming the QBCP semimetal into a Chern
insulator with a quantized anomalous Hall conductivity $sigma_xy =
Ce^2/hbar$, where the Chern number is governed by the polarization angle.
Moreover, the linear polarization preserves the central antisymmetry of the
Berry curvature, giving rise to a topological trivial insulator. These results
establish a tunable topological phase transition from a QBCP semimetal to Chern
insulator in the two-dimensional QBCP materials.
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