Superstructures arising from V trimers with orbital ordering in BaV10O15

Tomomasa Kajita,Takuro Katsufuji,Shigeo Mori,Hideki Kuwahara

doi:10.1103/physrevresearch.3.033046

Tomomasa Kajita, Takuro Katsufuji + Show 2 more

Open Access

https://doi.org/10.1103/physrevresearch.3.033046

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Abstract

In ${\mathrm{BaV}}_{10}{\mathrm{O}}_{15}$ with quasitriangular V lattices, we found unique superstructures characterized by $(qq0)$-type peaks in the momentum space, where $q$ varies continuously with temperature between $q=0$ and $1/3$ and locks at $1/3$. Such a threefold superstructure is likely caused by the dense arrangement of the V trimers associated with the orbital ordering of V. The results indicate that the superstructure of the V trimers, each of which is also a superstructure, gives rise to the ordered phases with peculiar characteristics.

Highlights

In crystals, superstructures of charge or spin with a period longer than that of the underlying lattice are often observed
In addition to the structural phase transition at Ts = 135 K, which is characterized by the alternate arrangement of V trimers caused by the V orbital ordering and lone V ions along the b axis, various ordered phases are found above Ts
Anomalies are observed in the resistivity, magnetic susceptibility, strain, and specific heat at Ttriple = 175 K and Tic ab = 210 K

Summary

Introduction

Superstructures of charge or spin with a period longer than that of the underlying lattice are often observed. Superstructures of charge are found in chargedensity-wave (CDW) states [1,2,3,4,5,6,7] and charge-ordered (CO) states [8,9,10], and superstructures of spin are found in spindensity-wave (SDW) states [11] and helical magnetic states [12,13] The period of these superstructures is dominated by the nesting vector of the Fermi surface, the number of carriers, or the magnitude ratio of two interactions, and can be a noninteger multiple of the lattice period, called incommensurate structures. It is known that the orbital degree of freedom that arises from localized d electrons in transition-metal compounds exhibits ordering, called orbital ordering In this orbitalordered (OO) state, specific states among the energetically degenerate orbitals are occupied by electrons at each site. The periods of the orbital ordering in these materials are commensurate with the unit cell, and no incommensurate orbital ordering has been reported so far, except for that of manganites, where OO and CO coexist [15]

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Discussion

Conclusion