| 1. |
- Lemasson, A., et al.
(author)
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Pair and single neutron transfer with Borromean He-8
- 2011
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In: Physics Letters B. - : Elsevier BV. - 0370-2693 .- 1873-2445. ; 697:5, s. 454-458
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Journal article (peer-reviewed)abstract
- Direct observation of the survival of Au-199 residues after 2n transfer in the He-8 + Au-197 system and the absence of the corresponding Cu-67 in the He-8 + Cu-65 system at various energies are reported. The measurements of the surprisingly large cross sections for Au-199, coupled with the integral cross sections for the various Au residues, is used to obtain the first model-independent lower limits on the ratio of 2n to in transfer cross sections from He-8 to a heavy target. A comparison of the transfer cross sections for He-6.8 on these targets highlights the differences in the interactions of these Borromean nuclei. These measurements for the most neutron-rich nuclei on different targets highlight the need to probe the reaction mechanism with various targets and represent an experimental advance towards understanding specific features of pairing in the dynamics of dilute nuclear systems.
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| 2. |
- Armstrong, Jeremy, et al.
(author)
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Interaction Blockade and Pairing in Two-Dimensional Finite Fermion Systems
- 2009
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In: Few-body Systems. - : Springer Science and Business Media LLC. - 0177-7963 .- 1432-5411. ; 45:2-4, s. 219-222
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Conference paper (peer-reviewed)abstract
- The properties of two-component fermionic quantum systems in two dimensions, such as they nowadays may be realized with cold atoms in traps, are studied within the pairing model adapted from nuclear physics. We compare the results with those of a full numerical diagonalization of the many-body Hamiltonian. The chemical potential differences, excitation energies and angular momentum spectra show that when the zero-range attractive interaction is varied in strength, strong odd-even effects, gaps and shell structure emerge.
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| 3. |
- Armstrong, J. R., et al.
(author)
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Complexity of quantum states in the two-dimensional pairing model
- 2012
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In: Physical Review E (Statistical, Nonlinear, and Soft Matter Physics). - 1539-3755. ; 86:6
-
Journal article (peer-reviewed)abstract
- It is known that many-fermion systems, such as complex atoms and nuclei, reveal (at some level of excitation energy) local signatures of quantum chaos similar to the predictions of random matrix theory. Here, we study the gradual development of such signatures in a model system of up to 16 fermions interacting through short-range pairing-type forces in a two-dimensional harmonic trap. We proceed from the simplest characteristics of the level spacing distribution to the complexity of eigenstates, strength, and correlation functions. For increasing pairing strength, at first, chaotic signatures gradually appear. However, when the pairing force dominates the Hamiltonian, we see a regression towards regularity. We introduce a "phase correlator" that allows us to distinguish the complexity of a quantum state that originates from its collective nature, from the complexity originating from quantum chaos. DOI: 10.1103/PhysRevE.86.066204
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| 4. |
- Åberg, Sven, et al.
(author)
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Mesoscopic fluctuations of the pairing gap
- 2008
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In: AIP CONFERENCE PROCEEDINGS. - : AIP. - 1551-7616 .- 0094-243X. ; 995, s. 173-184
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Conference paper (peer-reviewed)abstract
- A description of mesoscopic fluctuations of the pairing gap in finite-sized quantum systems based on periodic orbit theory is presented. The size of the fluctuations are found to depend on quite general properties. We distinguish between systems where corresponding classical motion is regular or chaotic, and describe in detail fluctuations of the BCS gap as a function of the size of the system. The theory is applied to different mesoscopic systems: atomic nuclei, metallic grains, and ultracold fermionic gases. We also present a detailed description of pairing gap variation with particle number for nuclei based on a deformed cavity potential.
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