engleski

Universality in few-body systems

We explore ground state properties of quantum few-body systems which consist of one, two or three different atom species. Stability of different clusters consisting of spin-polarized hydrogen, helium, neon, argon, alkali and alkaline earth isotopes is determined and their structure is analyzed. The study of realistic systems is supplemented by model calculations in order to fill gaps and test influence of the interaction potential model. For selected masses and interaction models exact ground-state estimates are obtained by the diffusion Monte Carlo method and pure estimators. Often special emphasis is given on a universality of quantum two- and three-body halo states [1, 2, 3], which prefer more to be in classically forbidden regions of space. Using dimensionless measures of the binding energy and cluster size, studied atomic clusters are compared to other known halos in different fields of physics. Different characteristic scaling lengths, which make size-energy ratio to be universal, are tested. As the scaled binding energy decreases, scaled size of samba and tango type trimers separate from Borromean type [3]. Here we make a step forward and extend size- energy universality to four- and five-body systems, starting with halo systems and tracking their behavior when going far away from the halo region toward strongly bound systems. In addition, connections between $(N+1)$- and $(N)$-body scaling relations are considered. Among structural properties we emphasize helium dimers and trimers which can be compared [4] with the most recent experimental results [5, 6, 7] obtained by Coulomb explosion imaging of diffracted clusters, and helium-alkali pentamers [8] which already indicate behavior noticed in nanodroplets. References [1] A. S. Jensen, K. Riisager, D. V. Fedorov, E. Garrido, Rev. Mod. Phys. 76, 215 (2004). [2] K. Riisager, Phys. Scr. T152, 014001 (2013). [3] P. Stipanović, L. Vranješ Markić, I. Bešlić, J. Boronat, Phys. Rev. Lett. 113, 253401 (2014). [4] P. Stipanović, L. Vranješ Markić, J. Boronat, J. Phys. B: At. Mol. Opt. Phys. 49, 185101 (2016). [5] J. Voigtsberger et al., Nature Communications 5, 5765 (2014). [6] M. Kunitski et al., Science 348, 551 (2015). [7] S. Zeller et al., PNAS 113, 14651 (2016). [8] P. Stipanović, L. Vranješ Markić, Few-Body Syst. 59, 45 (2018).

univerzalnost, mali broj čestica, kvantna halo stanja, kvantni Monte Carlo

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