Four-Particle Condensates in Nuclear Systems

Aseem Talukdar, Michael Ma, Fu‐Chun Zhang

GERD RÖPKE, Alexander Schnell, Peter Schuck +1 more

Four-particle correlations in fermion systems at finite temperatures are investigated with special attention to the formation of a condensate. Instead of the instability of the normal state with respect to the onset of pairing described by the Gorkov equation, a new equation is obtained which describes the onset of ``quartetting.'' Applying to symmetric nuclear matter, below a critical density, the four-particle condensation ( $\ensuremath{\alpha}$-like quartetting) is found to be favored over deuteron condensation (triplet pairing). This pairing-quartetting competition is expected to be a general feature of interacting fermion systems, such as the exciton-biexciton system in excited semiconductors. Possible experimental consequences are pointed out.

Hiroyuki Yabu

Yixin Guo, Hiroyuki Tajima, Haozhao Liang

We investigate the quartet correlations in four-component fermionic systems at the thermodynamic limit within a variational many-body theory. The Bardeen-Cooper-Schrieffer (BCS)--type variational wave function is extended to the systems with the coexistence of pair and quartet correlations at zero temperature. Special attention is paid to the application of the present framework to an $\ensuremath{\alpha}$-particle condensation in symmetric nuclear matter, where the coexistence of deuteron and $\ensuremath{\alpha}$ condensations is anticipated. We also discuss how physical properties, such as quasiparticle dispersion, can be modified by the pair and quartet correlations and show a hierarchical structure of in-medium cluster formations in infinite nuclear matter. The present results may also contribute to the interdisciplinary understanding of fermionic condensations beyond the BCS paradigm in many-body systems.

Peter Schuck, Yasuro Funaki, H. Horiuchi +3 more

M. Beyer

I present recent results on few-body correlations in nuclear matter at finite temperatures and densities. In particular I focus on the four-body correlations. The alpha-particle is the strongest bound state. The investigation is done based on effective in-medium few-body equations that consistently include self energy corrections and Pauli blocking effects. I address the question of four-body condensates as well.