Dual electronic states in thermoelectric cobalt oxide [ Bi 1.7 Ca 2 O 4 ] 0.59 CoO 2

Abstract : We investigate the low-temperature magnetic-field dependence of the resistivity in the thermoelectric misfit cobalt oxide Bi 1.7 Ca 2 O 4 0.59 CoO 2 from 60 K down to 3 K. The scaling of the negative magnetoresistance demonstrates a spin dependent transport mechanism due to a strong Hund's coupling. The inferred microscopic description implies dual electronic states, which explain the coexistence between localized and itinerant electrons both contributing to the thermopower. By shedding light on the electronic states, which lead to a high thermopower, this result likely provides potential way to optimize the thermoelectric properties.