Structures and Physical Properties of CsV$_2$Se$_{2-x}$O and V$_2$Se$_2$O

TL;DR

This study synthesizes new CsV$_2$Se$_{2-x}$O and V$_2$Se$_2$O compounds, characterizes their structures, and investigates their electrical and magnetic properties, revealing diverse behaviors and strong electron correlations.

Contribution

It reports the first synthesis and detailed characterization of CsV$_2$Se$_{2-x}$O and V$_2$Se$_2$O oxyselenides, highlighting their structural and electronic diversity.

Findings

CsV$_2$Se$_2$O shows semiconducting behavior.

CsV$_2$Se$_{1.5}$O exhibits metallic behavior.

V$_2$Se$_2$O displays insulating behavior with strong electron correlations.

Abstract

By using solid-state reactions, we successfully synthesize new oxyselenides CsV$_2$Se$_{2-x}$O (x = 0, 0.5). These compounds containing V$_2$O planar layers with a square lattice crystallize in the CeCr$_2$Si$_2$C structure with the space group of $P4/mmm$. Another new compound V$_2$Se$_2$O which crystallizes in space group $I4/mmm$ is fabricated by topochemical deintercalation of cesium from CsV$_2$Se$_2$O powder with iodine in tetrahydrofuran(THF). Resistivity measurements show a semiconducting behavior for CsV$_2$Se$_2$O, while a metallic behavior for CsV$_2$Se$_{1.5}$O, and an insulating feature for V$_2$Se$_2$O. A charge- or spin-density wave-like anomaly has been observed at 168 K for CsV$_2$Se$_2$O and 150 K for CsV$_2$Se$_{1.5}$O, respectively. And these anomalies are also confirmed by the magnetic susceptibility measurements. The resistivity in V$_2$Se$_2$O exhibits an anomalous log(1/$T$) temperature dependence, which is similar to the case in parent phase or very underdoped cuprates indicating the involvement of strong correlation. Magnetic susceptibility measurements show that the magnetic moment per V-site in V$_2$Se$_2$O is much larger than that of CsV$_2$Se$_{2-x}$O, which again suggests the correlation induced localization effect in the former.