Abstract
At finite temperatures, nuclear excitations are significantly modified, most notably through the emergence of additional low-energy dipole strength, which can critically impact astrophysical reaction rates. Ongoing fusion-evaporation experiments on Ni isotopes provide a unique opportunity to investigate the hot pygmy dipole strength (HPDS), underscoring the need for reliable theoretical predictions and a comprehensive understanding of this emerging phenomenon. In this work, the HPDS is investigated in Ni isotopes from$N = Z$to neutron-rich systems ( $^{56\text{--}70}$ Ni) over a temperature range of$T=$0 $-$ 2~MeV using the finite-temperature relativistic quasiparticle random phase approximation. In neutron-rich Ni isotopes, the pygmy dipole strength at higher temperatures exceeds up to 2.5 times its value observed at zero temperature. In contrast, near$N \approx Z$isotopes show negligible low-energy dipole strength at$T = 0$MeV but develop a pronounced HPDS as the temperature increases. Predicted E1 energy-weighted strength ( $S_{\text{EWS}}$ ) and cumulative$B$ (E1) values for HPDS are presented across the Ni isotopic chain for various low-energy intervals and temperatures, providing essential benchmarks to support and guide experimental studies.