Zhang, KunyanKunyanZhangDandu, MedhaMedhaDanduTUAN HUNG NGUYENZhang, TianyiTianyiZhangBarré, ElyseElyseBarréSaito, RiichiroRiichiroSaitoKong, JingJingKongRaja, ArchanaArchanaRajaHuang, ShengxiShengxiHuang2025-12-182025-12-182025-11-1119360851https://www.scopus.com/record/display.uri?eid=2-s2.0-105021303457&origin=resultslisthttps://scholars.lib.ntu.edu.tw/handle/123456789/734741Symmetry breaking in van der Waals materials enables the realization of quantum states and advanced device functionalities. Janus transition-metal dichalcogenides (TMDs) exhibit distinctive nonlinear optical properties due to their broken out-of-plane mirror symmetry. However, the dynamic control of second harmonic generation (SHG) anisotropy and resonance behavior via optical excitation remains elusive. In this work, we investigate the SHG response of Janus MoSSe/MoS2heterostructures with 2H and 3R stackings. We can tune the SHG response by varying the incident photon wavelength from 800 to 1000 nm, which shows a resonance-dependent enhancement in intensity and a deviation from 6-fold symmetry, indicating wavelength-dependent anisotropy. The ratio between maximum and minimum intensity in the armchair directions, associated with the SHG anisotropy, reaches a value of 1.73 at the excitation wavelength of 1000 nm. Group theory analysis and first-principles calculations reveal that the observed anisotropy arises from optically induced strain. Our findings highlight the role of symmetry breaking and optical resonance contributing to the optomechanical tuning of SHG anisotropy, offering opportunities for developing Janus TMD-based photonic devices for frequency conversion, light generation, and optical switching.falseinterlayer couplingJanus transition metal dichalcogenidesoptical resonanceoptostrictionsecond harmonic generationstrain[SDGs]SDG9journal article10.1021/acsnano.5c108612-s2.0-105021303457