Naslov
Nonisovalent La substitution in Sr14-y-x LayCaxCu24O41: switching the transport from ladders to chains

Autori
Vuletić, Tomislav ; Ivek, Tomislav ; Korin-Hamzić, Bojana ; Tomić, Silvia ; Gorshunov, Boris ; Haas, Philip ; Room, Thomas ; Dressel, Martin ; Akimitsu, J. ; Sasaki, T. ; Nagata, T.

Vrsta, podvrsta i kategorija rada
Sažeci sa skupova, sažetak, znanstveni

Izvornik
International Conference on the Low Energy Electrodynamics in Solids / Dressel, Martin - Stuttgart : Universitat Stuttgart, 2004

Skup
International Conference on the Low Energy Electrodynamics in Solids

Mjesto i datum
Bad Staffelstein, Njemačka, 18.07.2004. - 23.07.2004

Vrsta sudjelovanja
Poster

Vrsta recenzije
Nije recenziran

Ključne riječi
quasi-one-dimensional cuprates; spin chains; variable-range hopping; low-frequency dielectric spectroscopy; optical spectroscopy

Sažetak
We have studied the electric transport of the chain/ladder Sr14-y-xLayCaxCu24O41 quasi-one-dimensional (q1D) cuprates by dc resistivity, low frequency dielectric and optical spectroscopy. Stoichiometry indicates a maximum of six holes per formula unit, dh=6, which is reduced by non-isovalent La substitution y, dh=6-y. X-ray absorption (NEXAFS) experiments [1] have shown that for dh&#8804; 5 all holes reside in the chains, while for dh=6 at least one hole is transferred from the chains to the ladders. In the former materials we found [2] that dc conductivity sdc(T) follows Mott&#8217; s variable range hopping law, which changes to nearest-neighbor hopping above Tco&#8776; 300 K, characterized by simple activation, Fig.1. This indicates that for dh&#8804; 5 chains behave as a 1D disorder driven insulator, while for dh=6 they cross over into a charge-ordered (CO) state [3]. The CO phase in the chains coexists with charge-density wave (CDW) in the ladders [4, 5]. The high temperature (HT) phase, above the transition into the CDW ground state, is insulating due to strong electron-electron interactions. Room temperature ladder resistivity in this HT phase for dh=6 is at least 30 times lower than the extrapolated one in the chains for dh&#8804; 5, Fig.1. These findings confirm that the ladders behave as a q1D system with mobile carriers. However, the way how the transport switches from the chains to the ladders in 5< dh <6 range is still an open issue. Is there a phase transition from La-substituted to La-free materials and how the phase diagram of the former merges with the one of the latter should be resolved by a further study of materials with the total hole count 5< dh <6. [1] N. Nücker et al., Phys. Rev. B 62, 14384 (2000). [2] T.Vuletic et al., Phys.Rev.B 67, 184521 (2003). [3] M. Takigawa et al., Phys.Rev.B 57, 1124 (1998). [4] T.Vuletic et al., Phys.Rev.Lett. 90, 257002 (2003). [5] T.Vuletic et al., cond-mat/ (2003).

Izvorni jezik
Engleski

Znanstvena područja
Fizika

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