Light-engineered Multichannel Quantum Anomalous Hall Effect in High-order Topological Plumbene

Abstract

Floquet engineering severs as a forceful technique for uncovering high Chern numbers of quantum anomalous Hall (QAH) states with feasible tunability in high-order topologically insulating plumbene, which is readily accessible for experimental investigations. Under the irradiation of righthanded circularly polarized light, we predict a three-stage topological phase transition in plumbene, whether it is in a free-standing form or grown on h-BN. Initially, a metallic state evolves into a K(K')-valley-based QAH state with a Chern number of -8, which then decreases to -6 after the valley gap closes. Finally, a band inversion occurs at the $Γ$ point, resulting in a multichannel QAH state with C = -3. The trigonal warping model accounts for both K(K')-valley-based and $Γ$-pointbased QAH states. Additionally, growing plumbene on a non-van-der-Waals substrate eliminates the K(K')-valley-based topology, leaving only the $Γ$-point-based QAH state with C = +3. Our findings propose the tunability of various high Chern numbers derived from high-order topological insulators, aiming to advance the next-generation dissipationless electronic devices.

Figures (4)

• Figure 1: The evolution of the LDOS patterns in R-CPL-irradiated free-standing plumbene (at in-plane lattice constant as 5.08 Å and the light frequency of $\hbar\omega$ = 0.375 eV). (a) shows the side view (upper panel) and top view (lower pannel) of the plumbene under the irradiation of R-CPL, with the gray sphere representing the Pb atom. (b)-(e) provide a detailed presentation of the band inversion process and illustrate the $Y$-edge projected LDOS patterns at light intensities of 0.005 Å$^{-1}$, 0.056 Å$^{-1}$, 0.100 Å$^{-1}$ and 0.178 Å$^{-1}$, respectively. The total Chern number is indicated at the top of each subfigure, while the corresponding topological phase is shown at the bottom (Phases I, II, III stand for the Chern-insulating states with $C = -8$, $C = -6$ and $C = -3$ respectively). In each subfigure, the color gradient progresses from black to red and then to light-yellow, indicating an increase in LDOS values.
• Figure 2: A detailed analysis of the TPT process separately at the $K$ valley and the $\Gamma$ point: free-standing plumbene at in-plane lattice constant as 5.08 Å and $\hbar\omega$ = 0.375 eV. Panels (a)–(e) display the spin-resolved band evolutions around the $K$ valley, while panels (f)–(j) illustrate the zoomed-in Berry curvature distributions in the same region. The selected light intensities are 0.005 Å$^{-1}$, 0.060 Å$^{-1}$, 0.064 Å$^{-1}$, 0.068 Å$^{-1}$ and 0.080 Å$^{-1}$, respectively. In the band structures, the red and blue components represent spin up and down. In the Berry curvature plots, the red and blue regions indicate positive and negative chirality, respectively. Panels (k)–(t) provide a similar analysis around the $\Gamma$ point, with the light intensities chosen as 0.005 Å$^{-1}$, 0.120 Å$^{-1}$, 0.136 Å$^{-1}$, 0.150 Å$^{-1}$ and 0.170 Å$^{-1}$, respectively.
• Figure 3: Spin splitting and the contour distribution of phase diagrams in R-CPL-induced topologies of free-standing plumbene. The spin-resolved local gap evolution of free-standing plumbene under R-CPL irradiation at $\hbar\omega$ = 0.375 eV is shown around (a) the $\Gamma$ point and (b) the $K$($K'$) valley, respectively. The red and blue lines correspond to spin up and down accordingly. The contour distributions of (c) $\Gamma$-point local gaps, (d) $K$($K'$)-valley local gaps, and e global gaps across the entire Brillouin zone (BZ) are depicted as functions of light frequency ($x$-axis) and light intensity ($y$-axis). The color gradient transitions from blue to green and then to red, indicating an enhancement of the global gap. The maroon region represents the global gaps greater than 40 meV, while the metallic region is denoted in blue. The white dashed curves delineate the boundaries between different Chern number phases. Panels (a)-(e) are based on free-standing plumbene with in-plane lattice constant as 5.08 Å. Panel (f) is similar to (e) but illustrates the distributions as a function of biaxial strain ($x$-axis) and light intensity ($y$-axis) at $\hbar\omega$ = 0.375 eV.
• Figure 4: R-CPL-induced TPTs of plumbene grown on different substrates. Panel (a) provides the side view of plumbene/h-BN under the irradiation of R-CPL. The gray, light-gray and green balls stand for Pb, N and B atoms sequentially. Panels (b)–(e) illustrate the $Y$-edge projected LDOS patterns at light intensities of 0.005 Å$^{-1}$, 0.056 Å$^{-1}$, 0.100 Å$^{-1}$ and 0.178 Å$^{-1}$, respectively, with the light frequency as $\hbar\omega$ = 0.375 eV. The total Chern number is indicated at the top of each subfigure, while the corresponding topological phase is noted at the bottom. In each subfigure, the color gradient transitions from black to red and then to light-yellow, reflecting an increase in the LDOS values. Panels (f)-(j) depict the outcomes of plumbene/H-half-saturated-BaSe(111) in the same manner, but with the light intensities chosen as $A$ = 0.005 Å$^{-1}$, 0.100 Å$^{-1}$, 0.165 Å$^{-1}$ and 0.190 Å$^{-1}$ respectively in LDOS patterns, in which the light frequency is selected as 0.475 eV. Besides, the ching balls stand for Se atoms.