Formation of Nuclear-Polarized Phases of H Atoms Embedded in Solid H2 Films

We report on an experimental observation of two phases of hydrogen atoms in solid H2 films at temperatures of 0.1–0.8 K, characterized by a large enhancement of the nuclear spin polarization compared to that given by Boltzmann statistics (p=0.15 at T=0.15 K). The first phase with p=0.35(5) is formed...

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Bibliographic Details
Published in:Physical review letters 2019-06, Vol.122 (22), p.1
Main Authors: Sheludiakov, S, McColgan, P T, Lee, D M, Khmelenko, V V, Järvinen, J, Ahokas, J, Vasiliev, S
Format: Article
Language:English
Subjects:
Boltzmann distribution
Hydrogen atoms
Nuclear spin
Phase transitions
Polarization (spin alignment)
Sequences
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Summary:We report on an experimental observation of two phases of hydrogen atoms in solid H2 films at temperatures of 0.1–0.8 K, characterized by a large enhancement of the nuclear spin polarization compared to that given by Boltzmann statistics (p=0.15 at T=0.15 K). The first phase with p=0.35(5) is formed spontaneously during sample storage in a high magnetic field (B=4.6 T). The second phase with an even higher nuclear polarization, p=0.75(7), can be achieved at T≤0.55 K by repeating sequences of dynamic nuclear polarization followed by a system relaxation. Upon warming through the range 0.55–0.65 K, the highly nuclear-polarized phase undergoes a phase transition to the spontaneously polarized phase which breaks down at T≃0.8 K, and the nuclear polarization gradually converges to the Boltzmann distribution. We discuss possible scenarios for explaining the nature of the observed phenomena.
ISSN:0031-9007
1079-7114
DOI:10.1103/PhysRevLett.122.225301