Unraveling temperature-dependent electronic and optical shifts via single vacancy artificial defects on graphene

We present a thorough first-principles investigation of the temperature-dependent electronic, magnetic, and optical properties of graphene with a single vacancy defect. Spin-polarized states emerge near the Fermi level due to the breaking of sublattice symmetry caused by the vacancy, and localized electronic states are also observed. The system exhibits a significant enhancement in magnetic moment as the temperature increases from 300 K to 3000 K, reaching up to 2.00 μ B /cell, along with a more pronounced spin density localization around the defect. Analysis of the projected density of states (PDOS) shows a clear spin asymmetry in the defect-induced states, while charge density plots reveal a gradual delocalization of electrons with rising temperature. Furthermore, temperature-sensitive shifts and intensity changes are observed in the optical response, indicating reduced electronic coherence at elevated temperatures. The optical behavior is characterized by evaluating the dielectric function, refractive index, extinction coefficient, reflectivity, and energy loss function. These findings demonstrate that single-vacancy graphene maintains strong spin polarization across a wide temperature range and exhibits tunable optoelectronic properties, highlighting its potential for future spintronic and optoelectronic applications.