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arXiv · 1308.1831

Spin gap evolution upon Ca doping in the spin ladder series $Sr_{14-x}Ca_xCu_{24}O_{41}$ by inelastic neutron scattering

Guochu Deng·N. Tsyrulin·P. Bourges·D. Lamago·H. Ronnow·M. Kenzelmann·S. Danilkin·E. Pomjakushina·K. Conder
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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.

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Guochu Deng, N. Tsyrulin, P. Bourges, D. Lamago, H. Ronnow, M. Kenzelmann, S. Danilkin, E. Pomjakushina, K. Conder. 2013-08-08. Spin gap evolution upon Ca doping in the spin ladder series $Sr_{14-x}Ca_xCu_{24}O_{41}$ by inelastic neutron scattering. https://doi.org/10.1103/physrevb.88.014504

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