Ni-Driven Evolution of Pseudogap and Superconducting Gap in Underdoped Cuprate

A. Malinowski, V.L. Bezusyy, P. Nowicki Institute of Physics, Polish Academy of Sciences, al. Lotników 32/46, PL-02668 Warsaw, Poland

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In the presented study, Ni impurity is used to probe pseudogap and superconducting gap in the underdoped cuprate La1.85Sr0.15CuO4. The longitudinal magnetoresistance measurements reveal the presence of local maximum at the same temperature Tmax, below which zero-field resistivity in the parallel-resistor model deviates from its T2-dependence. Tracking the systematic evolution with Ni content y allows equating Tmax with pseudogap temperature T*. The rate of pseudogap closing by the magnetic field is consistent with the spin-paramagnetic effect, which is also the main pair-breaking process destroying superconductivity in the same field configuration. The thermal energy scale of pseudogap kBT* for y=0 is equal to the relevant magnetic Zeeman energy scale. With increasing y, both energy scales separate from each other. The increased Stoner factor is partially responsible for the enhancement of the Pauli effect and the decrease of the Zeeman limiting field with increased y.

DOI:10.12693/APhysPolA.143.134 topics: cuprate superconductors, pseudogap, effects of doping, Pauli paramagnetic effect