Experimental evidence of a liquid-liquid critical point in supercooled water
- Seonju You
- Marjorie Ladd-Parada
- Kyeongmin Nam
- Aigerim Karina
- Seoyoung Lee
- Myeongsik Shin
- Cheolhee Yang
- Yeseul Han
- Sangmin Jeong
- Kichan Park
- Kyeongwon Kim
- Minjeong Ki
- Robin Tyburski
- Iason Andronis
- Keely Ralf
- Jae Hyuk Lee
- Intae Eom
- Minseok Kim
- Rory Ma
- Dogeun Jang
- Fivos Perakis
- Peter H. Poole
- Katrin Amann-Winkel
- Kyung Hwan Kim
- Anders Nilsson
2026-03-26
The search for the liquid-liquid critical point in supercooled water is challenging owing to rapid crystallization. We studied supercooled water at timescales before ice formation by heating high- and low-density amorphous ices using infrared ultrafast laser pulses, followed by x-ray scattering. By varying the pump laser fluence, we accessed liquid states straddling the predicted critical point. We observed a crossover from a discontinuous to a continuous transition at which broad and slow structural variations occurred, consistent with critical fluctuations and slowing down. We also observed a rapid increase in the heat capacity indicating a critical divergence at 210 ± 8 K coincident with enhanced density fluctuations. These results suggest that our experiments have directly probed the vicinity of a critical point in supercooled water.