Photoinduced Transition between Conventional and Topological Insulators in Two-Dimensional Electronic Systems

Manipulating the topological properties of insulators, encoded in invariants such as the Chern number and its generalizations, is now a major issue for realizing novel charge or spin responses in electron systems. We propose that a simple optical means, subjecting to a driving laser field with circular polarization, can be fruitfully incorporated to this end. Taking as a prototypical example the two-band insulator first considered by Haldane, we show how the electron system can be tuned through phases associated with different Chern numbers as the laser intensity is adiabatically swept, i.e., a photoinduced analog of the quantum Hall plateau transition. The implications of our findings include the possibility of laser tuning a conventional insulator into a quantum spin Hall system.

Figure 1

The lattice structure considered in this study. Solid (open) dots denote sites belonging to the $A$ ($B$) sublattice. Electrons residing on the $A$ ($B$) sublattice suffer an on-site electron potential of $+\Delta$ ($-\Delta$).

Figure 2

The three-dimensional phase diagram of the normal and Chern insulators. (See text for details.)

Figure 3

(a) Partial section of the phase diagram for $\lambda =0$. In the filled area, one can traverse between the interior and exterior of the double-sheet structure by changing $\lambda$ within the interval $0<\lambda \lesssim \Lambda$. (b) Section of the phase diagram for $\varphi =\pm \pi /2$. (c) Corresponding Chern number as a function of $\lambda \in [{\lambda }^A,{\lambda }^B]$ for $\varphi =\pi /2$ (thick solid line) and $\varphi =-\pi /2$ (thick dashed line).