Carrier-doping-tunable ferroelectricity and ferromagnetism in elemental T-pentasilicene

The discovery of elemental two-dimensional (2D) ferroelectrics (FEs) offers a promising route toward ultrathin, energy-efficient electronic and spintronic devices. This work investigates a single-element 2D silicon allotrope with a corrugated pentagonal structure, namely T-pentasilicene, and reveals that both n-type and p-type carrier doping can effectively modulate the tilting height Δh, thereby enabling tunable FE polarization. This structural deformation induces a Mexican-hat-shaped valence band and pronounced band splitting near the Fermi level, arising from charge redistribution between inequivalent atoms that breaks local inversion symmetry. The resulting electronic asymmetry triggers a Stoner-type magnetic instability under moderate hole doping, enabling itinerant ferromagnetism. These findings establish T-pentasilicene as a rare elemental 2D system hosting coexisting FE ity and doping-induced ferromagnetism.