Dressed j-1/2 objects in mixed-valence lacunar spinel molybdates.

The lacunar-spinel chalcogenides exhibit magnetic centers in the form of transition-metal tetrahedra. On the basis of density-functional computations, the electronic ground state of an Mo tetrahedron has been postulated as single-configuration a e t, where a, e, and t are symmetry-adapted linear combinations of single-site Mo t atomic orbitals. Here we unveil the many-body tetramer wave-function: we show that sizable correlations yield a weight of only 62% for the a e t configuration.

Giant conductivity of mobile non-oxide domain walls.

Atomically sharp domain walls in ferroelectrics are considered as an ideal platform to realize easy-to-reconfigure nanoelectronic building blocks, created, manipulated and erased by external fields. However, conductive domain walls have been exclusively observed in oxides, where domain wall mobility and conductivity is largely influenced by stoichiometry and defects. Here, we report on giant conductivity of domain walls in the non-oxide ferroelectric GaVS.

Cooperative Cluster Jahn-Teller Effect as a Possible Route to Antiferroelectricity.

We report the observation of an antipolar phase in cubic GaNb_{4}S_{8} driven by an unconventional microscopic mechanism, the cooperative Jahn-Teller effect of Nb_{4}S_{4} molecular clusters. The assignment of the antipolar nature is based on sudden changes in the crystal structure and a strong drop of the dielectric constant at T_{JT}=31  K, also indicating the first-order nature of the transition. In addition, we found that local symmetry lowering precedes long-range orbital ordering, implying the presence of a dynamic Jahn-Teller effect in the cubic phase above T_{JT}.

Unusual dielectric response of 4-methyl-1,3-dioxolane derivatives.

In this paper, we applied broadband dielectric spectroscopy (BDS) to investigate the molecular dynamics of three 4-methyl-1,3-dioxolane derivatives (MD) whose chemical structures differ in the length of non-polar alkyl side chains. We notice that small changes within their chemical structures have a pronounced impact on parameters characterizing the supercooled dynamics of the compounds selected for this study. Our detailed analysis of the dielectric response reveals that in the supercooled-liquid state besides the structural α-relaxation a sub-α Debye-like relaxation can be clearly distinguished.

Architecture of nanoscale ferroelectric domains in GaMoS.

Local-probe imaging of the ferroelectric domain structure and auxiliary bulk pyroelectric measurements were conducted at low temperatures with the aim to clarify the essential aspects of the orbitally driven phase transition in GaMoS, a lacunar spinel crystal that can be viewed as a spin-hole analogue of its GaVS counterpart. We employed multiple scanning probe techniques combined with symmetry and mechanical compatibility analysis to uncover the hierarchical domain structures, developing on the 10-100 nm scale. The identified domain architecture involves a plethora of ferroelectric domain boundaries and junctions, including primary and secondary domain walls in both electrically neutral and charged configurations, and topological line defects transforming neutral secondary walls into two oppositely charged ones.