Observation of crystallization slowdown in supercooled para-hydrogen and ortho-deuterium quantum liquid mixtures

TL;DR

This study demonstrates that supercooled quantum liquid mixtures of para-hydrogen and ortho-deuterium exhibit a significant slowdown in crystallization rates, with experimental and simulation evidence highlighting quantum effects on crystallization dynamics.

Contribution

First experimental observation of quantum-origin crystallization slowdown in pH2-oD2 mixtures, supported by path-integral simulations revealing isotope-dependent quantum delocalization effects.

Findings

Crystallization rate is reduced in mixtures compared to pure substances.

Quantum delocalization differences lead to effective particle size variation.

Provides experimental benchmark for quantum behavior in supercooled liquids.

Abstract

We report a quantitative experimental study of the crystallization kinetics of supercooled quantum liquid mixtures of para-hydrogen (pH$_2$) and ortho-deuterium (oD$_2$) by high spatial resolution Raman spectroscopy of liquid microjets. We show that in a wide range of compositions the crystallization rate of the isotopic mixtures is significantly reduced with respect to that of the pure substances. To clarify this behavior we have performed path-integral simulations of the non-equilibrium pH$_2$-oD$_2$ liquid mixtures, revealing that differences in quantum delocalization between the two isotopic species translate into different effective particle sizes. Our results provide first experimental evidence for crystallization slowdown of quantum origin, offering a benchmark for theoretical studies of quantum behavior in supercooled liquids.