Zigzag chain order of LiVSe${}_2$ developing away from the vanadium trimer phase transition boundary

Abstract

The phenomenon of self-assembly of constituent elements to form molecules at low temperatures appears ubiquitously in transition metal compounds with orbital degrees of freedom. Recent progress in local structure studies using synchrotron radiation x-rays is shifting the interest in structural studies in such molecule-forming systems from the low-temperature ordered phase to the short-range order that appears like a precursor at high temperatures. In this study, we discuss both experimentally and theoretically the relationship between the trimer structure that appears in the layered LiV$X_2$ ($X$ = O, S, Se) system with a two-dimensional triangular lattice of vanadium and the zigzag chain-like local structure that appears near the phase transition boundary where molecular formation occurs. The vanadium trimerization that persistently appears in both low-temperature phases of LiVO${}_2$ and LiVS${}_2$ disappears in LiVSe${}_2$, and a regular triangular lattice is thought to be realized in LiVSe${}_2$, but this study reveals that the zigzag chain local distortion appears with a finite correlation length. This zigzag chain state local distortions are similar to the motif of local distortions in the high-temperature phase of LiVS${}_2$, indicating that the local distortions are persistent away from the trimer phase transition boundary. On the other hand, it is concluded that the zigzag chain order appearing in LiVSe${}_2$ is more stable than that in LiVS${}_2$ in terms of the temperature variation of atomic displacement and correlation length. The zigzag chain order is considered to be competitive with the trimer order appearing in the LiV$X_2$ system. In this paper, we discuss the similarities and differences between the parameters that stabilize these electronic phases and the local distortions that appear in other molecular formation systems.

References in corpus (10)

• Band Jahn-Teller Instability and Formation of Valence Bond Solid in a Mixed-Valent Spinel Oxide LiRh2O4
• Novel Superstructure-Phase Two-Dimensional Material 1$\text{T}$-VSe${}_2$ at High Pressure
• Regular-Triangle Trimer and Charge Order Preserving the Anderson Condition in the Pyrochlore Structure of CsW${}_2$O${}_6$
• Vanadium trimers randomly aligned along the c-axis direction in layered LiVO2
• Slow dynamics of disordered zigzag chain molecules in layered LiVS2 under electron irradiation
• Linear Trimer Formation by Three-Center-Four-Electron Bonding in RuP
• Observation of local atomic displacements intrinsic to the double zigzag chain structure of 1T-MTe2 (M = V, Nb, Ta)
• Short-range order and increased transition temperature in LiVO2 with weakened trimer frustration
• Robust atomic orbital in the cluster magnet LiMoO2
• Charge-ordered state satisfying the Anderson condition in LiRh2O4 arising from local dimer order