Pair-Correlation Effects in Many-Body Systems

J. Dobaczewski, Piotr Magierski, Witold Nazarewicz +2 more

Odd-even staggering of binding energies is studied in finite fermion systems with pairing correlations. We discuss contributions of the pairing and mean field to the staggering, and we construct the binding-energy indicators which measure the magnitude of pairing correlations and the effective single-particle spacings in a given system. The analysis is based on studying several exactly solvable many-body Hamiltonians as well as on the analytical formulas that can be applied in the weak and strong pairing limits.

Ivan Hubač, Andrzej J. Sadlej

Pina Romaniello

Sean S. Hodgman, R. I. Khakimov, Robert J. Lewis-Swan +2 more

In quantum many-body theory, all physical observables are described in terms of correlation functions between particle creation or annihilation operators. Measurement of such correlation functions can therefore be regarded as an operational solution to the quantum many-body problem. Here, we demonstrate this paradigm by measuring multiparticle momentum correlations up to third order between ultracold helium atoms in an s-wave scattering halo of colliding Bose-Einstein condensates, using a quantum many-body momentum microscope. Our measurements allow us to extract a key building block of all higher-order correlations in this system-the pairing field amplitude. In addition, we demonstrate a record violation of the classical Cauchy-Schwarz inequality for correlated atom pairs and triples. Measuring multiparticle momentum correlations could provide new insights into effects such as unconventional superconductivity and many-body localization.

Yugo Takahashi, Hideo Miyamoto, Kazuhiko Kuroki +1 more

We investigate the pairing state in a doped band insulator under a periodic driving field. We employ a correlated fermionic model on a honeycomb lattice, in which pairing glue is obtainable via repulsive interactions, and derive an effective model under circularly polarized light. We demonstrate that the effective pairing interaction for doped fermions obtained with the second-order perturbation theory is tunable by the frequency and amplitude of the driving field. We find the optimal frequency range to enhance the pairing interaction and show that the modified effective system can strengthen the two-body bound state. Our study suggests that external driving light can reinforce superconducting pair states in strongly correlated electron systems.

E. Krotscheck, C. E. Campbell