Spin gap evolution upon Ca doping in the spin ladder series $S{r}_{14-x}C{a}_{x}C{u}_{24}{O}_{41}$ by inelastic neutron scattering

Abstract

The spin gap evolution upon Ca doping in Sr14-xCaxCu24O41 was systematically investigated using inelastic neutron scattering. We discover that the singlet-triplet spin gap excitation survives in this series with x up to 13, indicating the singlet dimer ground state in these compounds. This observation corrects the previous speculation that the spin gap collapses at x~13 by the NMR technique. The strong intensity modulation along QH in x=0 gradually evolves into a Q-independent feature in x>11. This could be attributed to the localized Cu moment magnetism developing into an itinerant magnetism with increasing x. It is a surprise that the spin gap persists in the normal state of this spin ladder system with metallic behaviour, which evidences the possibility of magnetically-mediated carrier pairing mechanism in a two-leg spin ladder lattice.

17 pages, 6 figures

References in corpus (1)

• Macroscopic Quantum Coherence of the Spin Triplet in the Spin-Ladder Compound Sr14Cu24O41

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