Monovalent‐Copper (I; 3d10, S = 0) Induced Oxygen‐2p Valence Band Holes with Concomitant Attractive Interaction inside Low‐Dimensional Oxygen Networks

Results of electrical transport and magnetic measurements on coldpressed compacts of La2CuO4 and La1.70Ba0.30CuO4 provide strong evidence for their p‐type metallic and Pauli paramagnetic character at room temperature connected with the existence of low density‐of‐states oxygen‐2p valence band holes induced by ground state monovalent copper (3d10, S = 0). The host La2CuO4 exhibits an electronic phase transition at ≈85 K from a p‐type broad‐band metal (p = 2.5 × 10−2 holes/La2CuO4, μh = 10−4 m2/Vs, murn:x-wiley:03701972:media:PSSB2221420223:tex2gif-stack-1 = 0.5m0, EF = 0.26 eV, N(EF) = 0.15 states/eV‐La2CuO4) to a p‐type polaron‐mediated ICDW state (p ≈ 2.5 × 10−2 holes/La2CuO4, μh ≈ 10−4 m2/Vs, murn:x-wiley:03701972:media:PSSB2221420223:tex2gif-stack-2 ≈ 10m0, EF = 11 meV, N(EF) = 3.4 states/eV‐La2CuO4). The attractive interaction attending the O‐2p VB holes inside low‐dimensional oxygen networks is discussed in the framework of recent papers on structural distortions, electronic structures, and phase transitions in copper containing oxidic hosts and doped superconducting derivatives.