NMR and NQR study of pressure-induced superconductivity and the origin of critical-temperature enhancement in the spin-ladder cuprate Sr${}_2$Ca${}_{12}$Cu${}_{24}$O${}_{41}$

Abstract

Pressure-induced superconductivity was studied for a spin-ladder cuprate Sr${}_2$Ca${}_{12}$Cu${}_{24}$O${}_{41}$ using nuclear magnetic resonance (NMR) under pressures up to the optimal pressure 3.8 GPa. Pressure application leads to a transitional change from a spin-gapped state to a Fermi-liquid state at temperatures higher than $T_c$. The relaxation rate $1/T_1$ shows activated-type behavior at an onset pressure, whereas Korringa-like behavior becomes predominant at the optimal pressure, suggesting that an increase in the density of states (DOS) at the Fermi energy leads to enhancement of $T_c$. Nuclear quadrupole resonance (NQR) spectra suggest that pressure application causes transfer of holes from the chain to the ladder sites. The transfer of holes increases DOS below the optimal pressure. A dome-shaped $T_c$ versus pressure curve arises from naive balance between the transfer of holes and broadening of the band width.

References in corpus (13)

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Cited by in corpus (4)

• Absence of Luther-Emery Superconducting Phase in the Three-Band Model for Cuprate Ladders
• Valence Transition Theory of the Pressure-Induced Dimensionality Crossover in Superconducting Sr${}_{14-x}$Ca${}_x$Cu${}_{24}$O${}_{41}$
• Spin dynamics in the pressure-induced two-leg ladder cuprate superconductor Sr${}_{14-x}$Ca${}_x$Cu${}_{24}$O${}_{41}$
• Three-Dimensional Multiband d-p Model of Superconductivity in Spin-Chain Ladder Cuprate