Thermal compression of two-dimensional atomic hydrogen to quantum degeneracy

TL;DR

This study demonstrates thermal compression of 2D atomic hydrogen on superfluid helium, reaching high phase-space densities and providing the first direct measurement of the three-body recombination rate constant, which is lower than previous estimates.

Contribution

It presents the first direct measurement of the three-body recombination rate constant for 2D atomic hydrogen at ultra-low temperatures.

Findings

Achieved surface densities up to 5e12 1/cm^2 at ~100 mK.

Determined the upper bound of the three-body recombination rate constant as 2e-25 cm^4/s.

Found the recombination rate constant to be an order of magnitude smaller than previous experimental results.

Abstract

We describe experiments where 2D atomic hydrogen gas is compressed thermally at a small "cold spot" on the surface of superfluid helium and detected directly with electron-spin resonance. We reach surface densities up to 5e12 1/cm^2 at temperatures of approximately 100 mK corresponding to the maximum 2D phase-space density of about 1.5. By independent measurements of the surface density and its decay rate we make the first direct determination of the three-body recombination rate constant and get the value of 2e-25 cm^4/s for its upper bound, which is an order of magnitude smaller than previously reported experimental results.