Identical spin rotation effect and electron spin waves in quantum gas of atomic hydrogen

Abstract

Spin waves in quantum gases-the quality factor of the identical spin rotation effect L Lehtonen, O Vainio, J Ahokas et al. AbstractWe present an experimental study of electron spin waves in atomic hydrogen gas compressed to high densities of ∼5×10 18 cm −3 at temperatures ranging from 0.26 to 0.6 K in the strong magnetic field of 4.6 T. Hydrogen gas is in a quantum regime when the thermal de-Broglie wavelength is much larger than the s-wave scattering length. In this regime the identical particle effects play a major role in atomic collisions and lead to the identical spin rotation effect (ISR). We observed a variety of spin wave modes caused by this effect with strong dependence on the magnetic potential caused by variations of the polarizing magnetic field. We demonstrate confinement of the ISR modes in the magnetic potential and manipulate their properties by changing the spatial profile of the magnetic field. We have found that at a high enough density of H gas the magnons accumulate in their ground state in the magnetic trap and exhibit long coherence, which has a profound effect on the electron spin resonance spectra. Such macroscopic accumulation of the ground state occurs at a certain critical density of hydrogen gas, where the chemical potential of the magnons becomes equal to the energy of their ground state in the trapping potential.

Heisenberg's uncertainty principle in the PTOLEMY project: a theory update

“…It follows that a sufficiently high external magnetic field could force the pairs to be in spin triplet, hence preventing the molecular binding. Indeed, it has already been shown that in vacuum an external field of 4 − 5 T was capable of stabilizing atomic hydrogen at the temperature a few Kelvin [59,60]. Moreover, the low dimensionality of our systems might help stabilizing the atomic tritium against dimerization.…”

Searching for magnetostatic modes in spin-polarized atomic hydrogen

“…The ISRE leads to a propagation of the spin perturbation in the form of spin waves. In our recent work we found a large variety of the spin wave modes dependent on density of the gas, magnetic field gradients, and geometry of the sample [14,21,22]. We demonstrated a possibility of trapping and guiding [22] ISRE spin waves and compiled an argument for the existence of a Bose-Einstein condensate of magnons in atomic hydrogen [21].…”

“…Experiments are performed with a gas of atomic hydrogen in a strong magnetic field of 4.6 T in a temperature range of 300-500 mK. The gas is compressed to high densities up to ∼10×10 18 cm −3 using the piston of liquid helium in a U-tube like geometry, where the compression is driven by the fountain effect of superfluid 4 He [21]. Compression is performed by raising the helium level in a thin-walled polyimide tube of 0.5 mm diameter to a variable height ranging between 0.5 and 2 mm (see figure 1).…”

“…

We consider a possibility of the magnetostatic type spin waves driven by a long-range magnetic dipole interactions, to account for the peaks in the ESR spectra observed in our previous work [14]. The Walker equation for magnetostatic modes is solved for a cylinder of atomic hydrogen, first in a uniform magnetic field and second in a linearly decreasing magnetic field.

…”