High infrared transparency up to 8-μm-wavelength in correlated vanadium Wadsley conductors

Within industrial and military contexts, research on infrared transparent conductors (IR-TCs) has been limited due to the significant suppression of transparency by the free electron response. In this paper, we report that strong correlations between electrons play an important role in the development of a new strategy for fabricating IR-TCs. Metallic VO2(B) and V6O13 persistently exhibit transmittances 45% higher than that of Sn-doped In2O3 for a broad IR wavelength range of up to 8 μm. Based on electronic band structures determined quantitatively using x-ray absorption spectroscopy, x-ray photoemission spectroscopy, and spectroscopic ellipsometry, we propose that the enhancement in the IR-TC is attributed to the redshift of the plasma frequency induced by the correlated electrons.