Light Reveals the Crystal's Secrets
Shine light on an FePS3 crystal, and it responds with its own glow, like a neon sign, but much fainter and in the infrared range. This glow is not random: it depends on how the crystal is oriented. The scientists took samples from a thick chunk down to a single-atom layer and observed four emission bands — at 1.24 electronvolts, 1.79, 2.3, and 2.56.