Purely Spatial Quantum Diffusion of H Atoms in Solid H_{2} at Temperatures below 1 K

Area of Science:

• Quantum physics
• Condensed matter physics
• Materials science

Background:

• Atomic diffusion in solid molecular hydrogen (H2) is poorly understood at low temperatures.
• Previous studies relied on indirect methods like H atom recombination to infer H atom mobility.
• Understanding atomic transport in solid H2 is crucial for fields like quantum computing and astrophysics.

Purpose of the Study:

• To directly measure the quantum diffusion rate of H atoms in solid H2 films at ultralow temperatures.
• To investigate the influence of phonons on H atom mobility.
• To provide a more accurate characterization of H atom transport in solid H2.

Main Methods:

• Direct measurement of H atom quantum diffusion using a novel technique.
• Experiments conducted on solid H2 films at a temperature of 0.7 K.
• Controlled injection of phonons to study their effect on diffusion.

Main Results:

• A pure spatial diffusion rate of H atoms in H2 films was determined to be D^d = 5(2)×10^-17 cm^2 s^-1.
• This measured diffusion rate is two orders of magnitude faster than previously inferred values.
• H atom diffusion was observed to be significantly enhanced by the injection of phonons.

Conclusions:

• This study presents the first direct measurement of pure spatial diffusion for H atoms in solid H2.
• The findings challenge previous assumptions about H atom mobility in solid H2.
• Solid H2, alongside helium-3/helium-4 mixtures, is confirmed as a rare system exhibiting non-vanishing atomic diffusion below 1 K.