Di-neutron correlation in monopole two-neutron transfer modes in Sn isotope chain

TL;DR

This paper investigates the microscopic structure of monopole two-neutron transfer modes in neutron-rich Sn isotopes using QRPA, revealing di-neutron correlations and predicting a giant pair vibration near the neutron separation energy.

Contribution

It introduces a method to decompose transfer amplitudes into two-quasiparticle components and uncovers the role of high angular momentum states in di-neutron correlations.

Findings

Pair vibrational modes involve high-l quasiparticle states.

Coherent contributions suggest spatially correlated neutron pairs.

Prediction of a giant pair vibration near the neutron separation energy.

Abstract

We study microscopic structures of monopole pair vibrational modes and associated two-neutron transfer amplitudes in neutron-rich Sn isotopes by means of the linear response formalism of the quasiparticle random phase approximation(QRPA). For this purpose we introduce a method to decompose the transfer amplitudes with respect to two-quasiparticle components of the QRPA eigen mode. It is found that pair-addition ibrational modes in neutron-rich $^{132-140}$Sn and the pair rotational modes in $^{142-150}$Sn are commonly characterized by coherent contributions of quasaiparticle states having high orbital angular momenta $l \gesim 5$, which suggests transfer of a spatially correlated neutron pair. The calculation also predicts a high-lying pair vibration, the giant pair vibration, emerging near the one-neutron separation energy in $^{110-130}$Sn, and we find that they have the same di-neutron characters as that of the low-lying pair vibration in $^{132-140}$Sn.