Floquet Engineering of Nonequilibrium Valley-Polarized Quantum Anomalous Hall Effect with Tunable Chern Number

Abstract

Here, we propose that Floquet engineering offers a strategy to realize the nonequilibrium quantum anomalous Hall effect (QAHE) with tunable Chern number. Using first-principles calculations and Floquet theorem, we unveil that QAHE related to valley polarization (VP-QAHE) is formed from the hybridization of Floquet sidebands in the two-dimensional family MSi 2 Z 4 (M = Mo, W, V; Z = N, P, As) by irradiating circularly polarized light (CPL). Through the tuning of frequency, intensity, and handedness of CPL, the Chern number of VP-QAHE is highly tunable and up to C = ±4, which attributes to light-induced trigonal warping and multiple-band inversion at different valleys. The chiral edge states and quantized plateau of Hall conductance are visible inside the global band gap, thereby facilitating the experimental measurement. Our work not only establishes Floquet engineering of nonequilibrium VP-QAHE with tunable Chern number in realistic materials but also provides an avenue to explore emergent topological phases under light irradiation.

Exploring single-molecule interactions: heparin and FGF-1 proteins through solid-state nanopores

“…The characterization and discrimination of amyloid particles through nanopores further extend the scope of disease identification, allowing the observation of disease progression as these particles are identified as biomarkers associated with neurological diseases. 46,47 O'Donohue et al demonstrated the successful classification of the monomeric and dimeric forms of human serum transferrin receptor proteins through SSNs and confirmed the coexistence of both forms in a heterogeneous mixture. 48 The research findings of Yin et al exemplify the use of nanopores of varying diameters in the discrimination of ferritin and apo-ferritin, which display identical exterior structures and divergent interior structures.…”

Layer Control of Magneto-Optical Effects and Their Quantization in Spin-Valley Splitting Antiferromagnets

“…The SOC effect further breaks the degeneracy of two K valleys. The valley splitting Δ E valley can reach up to 98 meV at the conduction band edge, which is on the order of usual ferrovalley materials, such as monolayer Nb 3 I 8 , VSe 2 or VS 2 , , or VSi 2 N 4 or VSi 2 P 4 . ,,− In contrast to -symmetric antiferromagnetic materials, Figure h shows that the spin-conserving interband transitions (↑↑ + ↓↓) present an asymmetric distribution near two K valleys, which means the ↑↑ component can not cancel out the ↓↓ contribution. Notably, a finite spin-flip contribution emerges and also exhibits an unbalanced distributions around two K valleys (see Figure i), which is usually negligible small in most materials because the SOC energy scale is usually smaller than the exchange splitting energy scale. − The nonvanishing contributions both from spin-conserving and spin-flip processes, induced by the strong SOC effect and special spin-splitting, ultimately give rise to a measurable L-MOE, as shown in Figure j.…”

Engineering Layertronics in Two-Dimensional Ferromagnetic Multiferroic Lattice

“…Because of the simultaneous breaking of T - and P -symmetries, large Berry curvature is usually expected to exist at the band edges. Typical examples include the FM topological and valleytronics systems, wherein a large Berry curvature can emerge for the bands at the Γ and K points, respectively. − ,− Without loss of generality, we here focus on a 2D hexagonal lattice with C 3 z rotation symmetry and assume its conduction and valence band edges locate at the K and Γ points, respectively. It is noted that the mechanism proposed here is related to the C 3 z symmetry.…”

“…In solid-state physics, the geometric properties of wave functions are important physical quantities for fundamental physics and practical device applications in view of their striking physical effects on transport and thermodynamic properties of crystals. , Among the geometrical properties, Berry curvature is the most prominent quantity. − Berry curvature measures the electronic wave packet traversing a closed loop in the Brillouin zone, describing the entanglement of the bands. , Usually, symmetry breaking in crystalline solids can enable the existence of nonzero Berry curvature, which yields the striking Hall effect. ,,− For example, nonzero Berry curvature under time-reversal ( T ) symmetry breaking gives rise to a nonzero Chern number and thus the quantum anomalous Hall effect (QAHE), − while inversion ( P ) symmetry breaking leads to the valley Hall effect (VHE), − and they are related with distinct degrees of freedom, i.e., spin and valley, respectively. In recent years, these Hall effects have attracted broad interest and greatly promoted the fundamental research of condensed matter physics. − …”