Naslov
Collective Charge Excitations below the Metal-to-Insulator Transition in BaVS3

Autori
Ivek, Tomislav ; Vuletić, Tomislav ; Tomić, Silvia ; Akrap, Ana ; Berger, H ; Forro, Laszlo

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

Izvornik
XIII Training Course in the Physics of Strongly Correlated Systems / - Salerno, 2008

Skup
XIII Training Course in the Physics of Strongly Correlated Systems

Mjesto i datum
Salerno, Italija; Vietri sul Mare, Italija, 06.10.2008. - 17.10.2008

Vrsta sudjelovanja
Predavanje

Vrsta recenzije
Nije recenziran

Ključne riječi
metal-to-insulator transition; charge density wave; dielectric relaxation; orbital ordering

Sažetak
The perovskite-type sulfide the barium vanadium sulfide (BaVS3) consists of parallel VS3 spin chains separated by Ba atoms, which yields a quasi-one-dimensional structure. There are two electrons per unit cell which are shared between a broad A1g band derived from vanadium dz2 orbitals overlapping along the chain direction, and a quasi-degenerate narrow Eg1 band originating from e(t2g) orbitals with isotropic interactions via V-S-S-V bonds [1]. The spin degrees of freedom of the localized electrons together with coupling of itinerant and localized electrons give rise to a novel and complex physics, resulting in a MI transition [2, 3] at about 70 K and a magnetic transition at about 30 K. In spite of a great deal of experimental efforts, no definite understanding has been reached yet on the detailed nature of the MI phase transition and the ground state in BaVS3. We have characterized charge response in BaVS3 single crystals by dc resistivity and low frequency dielectric spectroscopy [4]. A broad relaxation mode in MHz range with a huge dielectric constant ~= 10^6 emerges at the metal-to-insulator phase transition TMI ~= 67 K, weakens with lowering temperature and eventually levels off below the magnetic transition Tchi ~= 30 K. The mean relaxation time is thermally activated in a manner similar to the dc resistivity. These features are interpreted as signatures of short-wavelength charge excitations characteristic for the orbital ordering which sets in at TMI and develops a long-range order below Tchi. References: [1] F. Lechermann et al., Phys. Rev. B 76, 085101 (2007). [2] S. Fagot et al., Phys. Rev. Lett. 90, 196401 (2003). [3] S. Fagot et al., Phys. Rev. B 73, 033102 (2006). [4] T. Ivek et al., accepted for publication in Phys. Rev. B, arXiv:0706.2079v4 (2008).

Izvorni jezik
Engleski

Znanstvena područja
Fizika

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