2025, Strain-Driven Symmetry Breaking and Enhanced SHG in Centrosymmetric 1T-PtS2, Journal of Physical Chemistry Letters(cover image).
2025, Strain-Driven Symmetry Breaking and Enhanced SHG in Centrosymmetric 1T-PtS2, Journal of Physical Chemistry Letters.
Abstract:
Second-harmonic generation (SHG) in two-dimensional (2D) materials typically requires broken inversion symmetry, posing a fundamental constraint for nonlinear optical applications. Surprisingly, the SHG phenomenon recently observed in centrosymmetric 1T-phase transition metal disulfide compounds (1T-TMDs), but its underlying mechanism and tunability remain elusive. Here, taking the centrosymmetric 1T-PtS2 as an example, we investigate the SHG responses and origin, finding a surprising giant SHG response, exhibiting intensities up to 15 times greater than non-centrosymmetric monolayer WS2 under same excitation conditions. This is attributed to the sensitive response of SHG in 1T-PtS2 to tiny strain introduced by the mechanical exfoliation, which is confirmed by the anisotropic six-petal polarization pattern. By engineering a controlled strain environment using patterned Au pillars and Si hole arrays, we enhanced the SHG signal by a factor of three, further indicating exceptional strain sensitivity of the 1T phase. Theoretical calculations reveal that strain disrupt lattice symmetry and disturb uniform charge distribution of 1T-PtS2, which induces the SHG. Our results provide new insights into central symmetry structure-induced second harmonics, and establish a foundation for developing the next generation of ovel functional SHG devices.
Keywords: Nonlinear optics, second-harmonic generation, platinum disulfide, strain, first principles calculation.
Link: https://pubs.acs.org/doi/10.1021/acs.jpclett.5c01731
zhang-et-al-2025-strain-driven-symmetry-breaking-and-enhanced-shg-in-centrosymmetric-1t-pts2.pdf