Resonating Valence Bond Mechanism of Impurity Band Superconductivity in Diamond

Superconductivity in an uncompensated boron doped diamond, a very recent observation, is strikingly close to an earlier observation of Anderson–Mott insulator to metal transition, prompting us to suggest an electron correlation driven superconductivity in an impurity band. Random coulomb potential remove a three fold orbital degeneracy of boron acceptor states, resulting in an effective single, narrow, tight binding and half-filled band of holes. Singlet coupling between spins of neighboring neutral acceptors B ⁰–B ⁰ is the seed of pairing. Across the insulator to metal transition, a small and equal fraction of charged B ⁺ and B ⁻ states (free carriers) get spontaneously generated and delocalize. Thereupon neutral singlets resonate and get charged resulting in a resonating valence bond (RVB) superconducting state.