Doping-induced itinerant ferromagnetism and enhanced ferroelectricity in bilayer InSe
Phys. Rev. Applied 26, 014049 – Published 16 July, 2026
DOI: https://doi.org/10.1103/sbfw-ygb7
Abstract
The microscopic coexistence of ferroelectricity and ferromagnetism in solids remains a fundamental challenge in condensed matter physics, with far-reaching implications for multifunctional materials and next-generation electronic devices. Using first-principles calculations, we predict emergent sliding ferroelectricity and doping-mediated ferromagnetism in bilayer (BL) InSe. The energetically favored AB-stacked BL-InSe spontaneously breaks the out-of-plane mirror symmetry, resulting in a switchable polarization with a saturated component of 0.089 pC/m and a low transition barrier of 28.8 meV per unit cell. Strikingly, low-concentration electrostatic doping enhances rather than suppresses the ferroelectric polarization due to the abnormal layer-dependent electronic occupation in BL-InSe, in contrast to the conventional screening paradigm. In addition, the characteristic Mexican-hat-shaped valence band enables doping-induced itinerant half-metallic ferromagnetism, where the interlayer spin density difference scales linearly with doping concentration and can be reversed by switching the polarization direction, revealing a direct coupling between polarization and spin degrees of freedom. These results demonstrate the coexistence of ferroelectric and ferromagnetic orders in BL-InSe and establish a viable platform for realizing voltage-tunable multiferroicity through stacking and carrier doping in otherwise nonpolar and nonmagnetic semiconductors.
