Electronic correlation-driven orbital polarization transitions in the orbital-selective Mott compound <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mrow><mml:msub><mml:mi>Ba</mml:mi><mml:mn>2</mml:mn></mml:msub><mml:msub><mml:mi>CuO</mml:mi><mml:mrow><mml:mn>4</mml:mn><mml:mo>−</mml:mo><mml:mi>δ</mml:mi></mml:mrow></mml:msub></mml:mrow></mml:math>

The electronic states near the Fermi level of recently discovered superconductor ${\mathrm{Ba}}_{2}{\mathrm{CuO}}_{4\ensuremath{-}\ensuremath{\delta}}$ consist primarily Cu ${d}_{{x}^{2}\ensuremath{-}{y}^{2}}$ and ${d}_{3{z}^{2}\ensuremath{-}{r}^{2}}$ orbitals. We investigate correlation effect orbital polarization an effective two-orbital Hubbard model mimicking low-energy physics in hole-rich regime by utilizing dynamical mean-field theory with Lanczos method as impurity solver. find that hole-overdoped $3{d}^{8}$ (${\mathrm{Cu}}^{3+}$) is orbital-selective Mott phase (OSMP) at half-filling, typical feature remains when electron filling approaches ${n}_{e}\ensuremath{\sim}2.5$, which closely approximates to experimental hole doping for emergence high-${T}_{c}$ superconductivity. also obtain very stable OSMP, multiorbital can drive transitions. These results indicate OSMP polarization, local magnetic moment, spin or fluctuations still exist. propose our present are applicable ${\mathrm{Sr}}_{2}{\mathrm{CuO}}_{4\ensuremath{-}\ensuremath{\delta}}$ other cuprates, demanding unconventional superconducting scenario cuprates.