The first far-infrared absorption spectra of manganite samples at pressures $P$ up to 10 GPa were obtained on ${\mathrm{La}}_{1-x}{\mathrm{Ca}}_x{\mathrm{MnO}}_{3-y}$ by use of synchrotron radiation. For $x=0.25$ and 0.20 ($y=0$), $P$ promotes partial metallization at room temperature through a strong reduction of the insulating gap. An $x=0.20$ sample with $y=0.08$ does not show any charge delocalization effect up to 10 GPa. An Urbach-like model of disordered Jahn-Teller wells is shown to well fit the far-infrared band edge and allows one to obtain a reliable pressure dependence of the energy gap.

• Received 3 August 2005

DOI:https://doi.org/10.1103/PhysRevLett.96.035503