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arXiv · 1310.5342

Conventional BCS, Unconventional BCS, and Non-BCS Hidden Dineutron Phases in Neutron Matter

V. A. Khodel·J. W. Clark·V. R. Shaginyan·M. V. Zverev
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Abstract

The nature of pairing correlations in neutron matter is re-examined. Working within the conventional approximation in which the $nn$ pairing interaction is provided by a realistic bare $nn$ potential fitted to scattering data, it is demonstrated that the standard BCS theory fails in regions of neutron number density where the pairing constant $λ$, depending crucially on density, has a non-BCS negative sign. We are led to propose a non-BCS scenario for pairing phenomena in neutron matter that involves the formation of a hidden dineutron state. In low-density neutron matter where the pairing constant has the standard BCS sign, two phases organized by pairing correlations are possible and compete energetically: a conventional BCS phase and a dineutron phase. In dense neutron matter, where $λ$ changes sign, only the dineutron phase survives and exists until the critical density for termination of pairing correlations is reached at approximately twice the neutron density in heavy atomic nuclei.

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V. A. Khodel, J. W. Clark, V. R. Shaginyan, M. V. Zverev. 2013-10-20. Conventional BCS, Unconventional BCS, and Non-BCS Hidden Dineutron Phases in Neutron Matter. https://doi.org/10.1134/s1063778814080109

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