Tuning the thermodynamic ordering of strongly correlated protons in ice by angstrom-scale interface modification

The static and dynamic behaviour of strongly correlated many-body protons in nanoscale hydrogen-bond networks plays crucial roles in a wide range of physicochemical, biological and geological phenomena in nature. However, because of the difficulty of probing and manipulating the proton configuration in nanomaterials, controlling the cooperative behaviour of many-body protons remains challenging. By combining proton-order sensitive nonlinear optical spectroscopy and well-defined interface modification at molecular/atomic scale, we demonstrate the possibility of extensively tuning the emergent physical properties of strongly correlated protons beyond the thermodynamic constraints of bulk hydrogen bonds. Focusing on heteroepitaxially grown crystalline ice films as a model of a strongly correlated and frustrated proton system, we show that the emergence and disappearance of a high-Tc proton order on the nano- to mesoscale is readily switched by angstrom-scale interface engineering. These results pave a way to designing and controlling emergent properties of correlated proton systems. The ordering and dynamics of protons in nanoscale hydrogen-bond networks are crucial for a wide range of physicochemical, biological and geological phenomena in nature. Here, combining vibrational spectroscopy and Angstrom-scale interface engineering of crystalline ice films, an extensive tuning of strongly correlated proton ordering is demonstrated beyond the thermodynamic constraints of bulk hydrogen bonds.