Anomalously low dielectric constant of confined water
Abstract
The dielectric constant of interfacial water has been predicted to be smaller than that of bulk water (= 80) because the rotational freedom of water dipoles is expected to decrease near surfaces, yet experimental evidence is lacking. We report local capacitance measurements for water confined between two atomically-flat walls separated by various distances down to 1 nm. Our experiments reveal the presence of an interfacial layer with vanishingly small polarization such that its out-of-plane dielectric constant is only approximately 2. The electrically dead layer is found to be two to three molecules thick. These results provide much needed feedback for theories describing water-mediated surface interactions and behavior of interfacial water, and show a way to investigate the dielectric properties of other fluids and solids under extreme confinement.
Keywords
Cite
@article{arxiv.1806.04486,
title = {Anomalously low dielectric constant of confined water},
author = {L. Fumagalli and A. Esfandiar and R. Fabregas and S. Hu and P. Ares and A. Janardanan and Q. Yang and B. Radha and T. Taniguchi and K. Watanabe and G. Gomila and K. S. Novoselov and A. K. Geim},
journal= {arXiv preprint arXiv:1806.04486},
year = {2025}
}