Strong-Field Control of a van der Waals Antiferromagnet MnPS₃

Groundbreaking advances in laser technology has allowed for optical manipulation of quantum materials on ultrafast timescales. Exciting a material using intense laser pulses and pushing it out of equilibrium may enable discovery of myriad novel collective excitations which cannot be revealed by static parameters, i.e., pressure, temperature etc. Recently, significant efforts have been made in strong-field periodic driving with light having energy below a material band gap. Such a photoexcitation protocol holds exciting possibilities to modulate nonlinear optical properties as well as uncover phenomena that are otherwise inaccessible via driving above the band gap. This is accomplished using mid-infrared (MIR) or terahertz (THz) pulses. We target 2D van der Waals antiferromagnet (AFM) MnPS₃that exhibits a Néel-type AFM ordering below K and a charge-transfer band gap of 3 eV. Previously, optical absorption and resonant inelastic X-ray scattering have revealed multiple onsite transition peaks below the band gap, and photoexciting below and above these transitions have produced strikingly different results. Here, we use strong-field below-gap pumping schemes ranging from nonlinear THz to MIR, and combine them with a suite of probing techniques. Thus, we delineate the dynamical attributes of MnPS₃ such as coherent phonons and light-induced shift of spectral weight that scales with the AFM order. Our study unravels intriguing signatures of nonlinear coupling between electron, lattice and magnetism, and can shed light towards efficient controlling of quantum magnets in strong-field regime.