The discovery of superconductivity with a critical temperature of 80~K in
La3βNi2βO7β under pressure has received enormous attention.
La3βNi2βO7β is not superconducting under ambient pressure but
exhibits a density-wave-like transition at Tββ115~K.
Understanding the electronic correlations, charge dynamics and dominant
orbitals are important steps towards the mechanism of superconductivity and
other instabilities. Here, our optical study shows that La3βNi2βO7β
features strong electronic correlations which significantly reduce the
electron's kinetic energy and place it in the proximity of the Mott phase. The
low-frequency optical conductivity reveals two Drude components arising from
multiple bands dominated by the Ni-dx2βy2β and Ni-d3z2βr2β
orbitals at the Fermi level. Above Tβ, the scattering rates for both
Drude components vary linearly with temperature, indicating non-Fermi-liquid
behavior which may be associated with spin-fluctuation scattering. Below
Tβ, a gap opens in the Ni-d3z2βr2β orbital, suggesting the
importance of the Ni-d3z2βr2β orbital in the density-wave-like
instability. Our experimental results provide key insights into the mechanism
of the density-wave-like order and superconductivity in
La3βNi2βO7β.Comment: 26 pages, 4 figures, Comments are welcome and appreciate