Layer Hall effect induced by hidden Berry curvature in antiferromagnetic insulators

Abstract

The layer Hall effect describes electrons spontaneously deflected to opposite sides at different layers, which has been experimentally reported in the MnBi2Te4 thinfilms under perpendicular electric fields [Gao et al., Nature 595, 521 (2021)]. Here, beyond the scenario of $\mathcal {PT}$-symmetry breaking in the experiment, we reveal a universal origin of the layer Hall effect in terms of the so-called hidden Berry curvature, as well as material design principles. Hence, it gives rise to zero Berry curvature in momentum space but nonzero layer-locked hidden Berry curvature in real space. We show that compared to that of a trivial insulator, the layer Hall effect is significantly enhanced in antiferromagnetic topological insulators. Our universal picture provides a paradigm for revealing the hidden physics as a result of the interplay between the global and local symmetries, and can be generalized in various scenarios.

Renormalizing Antiferroelectric Nanostripes in β′-In2Se3 via Optomechanics

“…Similar photocurrents of the same order of magnitude are also calculated in AF 1 and AF 2 (Figure S6). This nanostripe-specific photocurrent is similar as in the recently disclosed concept of hidden spin polarization, hidden Berry curvautre, and hidden Hall current . In all of these cases, the total response functions of the system are zero, subject to specific (usually inversion or time-reversal) symmetries, but once we project them into a partial sector, they would show finite and observable signals.…”

“…This nanostripe-specific photocurrent is similar as in the recently disclosed concept of hidden spin polarization, 55 hidden Berry curvautre, 56 and hidden Hall current. 57 In all of these cases, the total response functions of the system are zero, subject to specific (usually inversion or time-reversal) symmetries, but once we project them into a partial sector, they would show finite and observable signals. The fundamental mechanism is that the local symmetry of each nanostripe is lower than that of the whole system, and the removal of mirror reflection along the x direction yields finite and observable BPV currents.…”

Chiral Dirac fermion in a collinear antiferromagnet

“…Due to the symmetry operation of time-reversal combined with nonsymmorphic translation (see Supplementary S5.1, Table S4), bulk CoNb 3 S 6 cannot exhibit nite anomalous Hall conductivity. However, rather than being intrinsically absent, the Berry curvature originated from the nontrivial bands are large yet compensated by the global high symmetry 33,34 . Therefore, the small ferromagnetic (FM) tilting along the z-axis and nite SOC play a role of symmetry breaking that reveals the large Berry curvature effect hidden in the otherwise doubly degenerate bands, thus leading to nite anomalous Hall effect.…”

Tunable Topological States in Stacked Chern Insulator Bilayers

“…Study of the topological states in low dimensions under strong magnetic fields can be traced back to the quantum Hall plateaus first observed in two-dimensional (2D) electron systems . Since the experimental observation of quantum anomalous Hall (QAH) effect in Cr-doped (Bi, Sb) 2 Te 3 , , a large number of multilayer-stacked van der Waals (vdW) magnetic topological materials and tailored alternating magnetic-doped TI heterostructures have been designed and synthesized, which greatly increases the QAH working temperature and enriches topological quantum phases in low dimensions. − For instance, topological phase transitions are introduced in the MnBi 2 Te 4 family modulated by external magnetization, magnetic anisotropy, and electric fields, with both strong spin–orbit coupling (SOC) and time-reversal symmetry breaking under concern. − Tunable high-Chern-number QAH states are further realized, − and the layer Hall effect (LHE), where electrons with the opposite layer degree of freedom respond to external fields differently, is proposed and explained by hidden Berry curvature singularity. , Nevertheless, nontrivial topological states can be preserved only when the MnBi 2 Te 4 septuple layers are multilayer-stacked and bulk-phase orientated rather than being atomically thin . Stacked Chern insulators bilayers, however, which are more flexible in responding to external fields, will naturally provide an excellent platform to study tunable topological phase transitions.…”