Antiferromagnetism-induced second-order nonlinear optical responses of centrosymmetric bilayer CrI3

Abstract

Antiferromagnetism (AF) in AB ′-stacked centrosymmetric bilayer (BL) CrI 3 breaks both spatial inversion (P) and time-reversal (T) symmetries but maintains the combined P T symmetry, thus inducing novel second-order nonlinear optical (NLO) responses such as second-harmonic generation (SHG), linear electric-optic effect (LEO) and bulk photovoltaic effect (BPVE). In this work, we calculate AF-induced NLO responses of the BL CrI 3 based on the density functional theory with the generalized gradient approximation (GGA) plus onsite Coulomb correlation (U), i.e., the GGA+U method. Interestingly, we find that the magnetic SHG, LEO and photocurrent in the AF BL CrI 3 are huge, being comparable or even larger than that of the well-known nonmagnetic noncentrosymmetric semiconductors. For example, the calculated SHG coefficients are in the same order of magnitude as that of MoS 2 monolayer (ML), the most promising 2D material for NLO devices. The calculated LEO coefficients are almost three times larger than that of MoS 2 ML. The calculated NLO photocurrent in the CrI 3 BL is among the largest values predicted so far for the BPVE materials. On the other hand, unlike nonmagnetic semiconductors, the NLO responses in the AF BL CrI 3 are nonreciprocal and also switchable by rotating magnetization direction. Therefore, our interesting findings indicate that the AF BL CrI 3 will not only provide a valuable platform for exploring new physics of low-dimensional magnetism but also have promising applications in magnetic NLO and LEO devices such as frequency conversion, electro-optical switches, and light signal modulators as well as high energy conversion efficiency photovoltaic solar cells.

Reparative and Maladaptive Inflammation in Tendon Healing

“…The release of type II cytokines promotes polarization of innate and adaptive immune cells toward anti-inflammatory phenotypes that induce immune tolerance and release growth factors (such as amphiregulin and TGFβ) that stimulate resident stem and progenitor cell proliferation and recruitment ( Burzyn et al, 2013 ; Eming et al, 2017 ; Ito et al, 2019 ; Minutti et al, 2019 ). Inadequate reparative responses of stem and progenitor cells or immune dysregulation can alternatively recruit myofibroblasts that deposit dense collagen resulting in scar tissue formation or fibrosis ( Gudelli and Guo, 2020 ).…”

Basic formulation and first-principles implementation of nonlinear magneto-optical effects

“…The correction to ensure U(2)-gauge invariant is essential in the presence of PT symmetry which hasn't been Our results are in red solid line, while the results in Ref. [61] are in blue dashed line. The coordinate was set to be the same as Ref.…”

“…In this case, only magnetic responses including MIC, MSC and magnetization-sensitive SHG are present while normal responses NIC, NSC and non-magnetic SHG are forbidden, which makes them a simple platform to investigate the nonlinear magneto-optical responses. Additionally, both materials are feasible in experiments [21,60] and their MIC has been studied theoretically in literature [12,13,61], which provides valuable results for comparison. For bilayer MnBi 2 Te 4 , we considered ABtype stacking (same stacking pattern as in bulk) in which each layer laterally shifted by [1/3, 1/3, 0].…”

“…The MIC of bilayer MnBi 2 Te 4 and bilayer CrI 3 have been calculated recently [13,61]. Although previous works haven't considered the U(2)-gauge problem under PT symmetry, fortunately, MIC is not subjected to modifications in PT symmetric case as demonstrated in Eq.…”

“…For bilayer CrI 3 , in order to compare the band struc- The Cartesian coordinates adopted in our calculations are marked by solid lines and the one adopted in Ref. [61] are in the dashed line.…”