Critical temperature for quenching of pair correlations

Abstract

The level density at low spin in the 161,162-Dy and 171,172-Yb nuclei has been extracted from primary gamma rays. The nuclear heat capacity is deduced within the framework of the canonical ensemble. The heat capacity exhibits an S-formed shape as a function of temperature, which is interpreted as a fingerprint of the phase transition from a strongly correlated to an uncorrelated phase. The critical temperature for the quenching of pair correlations is found at Tc=0.50(4) MeV.Comment: 8 pages including 4 figures, different method to extract Tc, different figures, text partly rewritte

Nuclear moment of inertia and spin distribution of nuclear levels

“…This would introduce five additional integration variables in the SPA integral (20), two representing the intrinsic deformation and three representing the orientation of the deformed field [16]. This integration over the Euler angles of the intrinsic frame is equivalent to the symmetry restoration described by (82).…”

“…Rather then using Eqs. (7) and (8) with the full Hamiltonian H, we first apply an SPA representation similar to (20) but for the cranked Hamiltonian in (6), and then calculate the intrinsic moments from I ii = ∂ 2 F (β, ω)/∂ω 2 i | ω=0 . If this is done starting from the canonical partition function in (6), we obtain the following expression…”

Quantum number projection at finite temperature via thermofield dynamics

“…Although the superfluid-to-normal phase transition has been predicted to occur at relatively low temperature (0.5 T c 1 MeV) [18,24,25], it is not yet well established in nuclei. Based on a precise measurement of nuclear level densities, the superfluid-to-normal transition in nuclei has been discussed recently [26]. While there is no sharp discontinuity as in infinite systems, the S-shape behavior in the graph of heat capacity vs. temperature, C(T ), has been argued to be a signature of the transition [26,27].…”

“…Based on a precise measurement of nuclear level densities, the superfluid-to-normal transition in nuclei has been discussed recently [26]. While there is no sharp discontinuity as in infinite systems, the S-shape behavior in the graph of heat capacity vs. temperature, C(T ), has been argued to be a signature of the transition [26,27]. For proper understanding of the phase transition and its relation to the S-shape, it is important to investigate effect of the quantum fluctuations in connection with the conservation laws, although the other quantum fluctuations cannot be neglected in quantitative description [28], particularly around the critical temperature.…”

“…The projection operator with respect to the space parity can be expressed in the form similar to Eq. (26), with the integral converted to a discrete sum,…”