Cascading transitions toward unconventional charge density wave states in the quasi-two-dimensional monophosphate tungsten bronze P4W16O56.

Elen Duverger-Nédellec,Alain Pautrat,Olivier Pérez,Kamil K Kolincio,Laurence Hervé

doi:10.1107/s2052252519016695

Abstract

Single crystals of the m = 8 member of the low-dimensional monophosphate tungsten bronzes (PO2)4(WO3)2m family were grown by chemical vapour transport technique and the high crystalline quality obtained allowed a reinvestigation of the physical and structural properties. Resistivity measurements revealed three anomalies at T C1 = 258 K, T C2 = 245 K and T C3 = 140 K, never observed until now. Parallel X-ray diffraction investigations showed a specific signature associated with three structural transitions, i.e. the appearance of different sets of satellite reflections below T C1, T C2 and T C3. Several harmonics of intense satellite reflections were observed, reflecting the non-sinusoidal nature of the structural modulations and a strong electron-phonon coupling in the material. These transitions could be associated with the formation of three successive unconventional charge density wave states.

Highlights

Monophosphate tungsten bronzes with pentagonal tunnels (MPTBp) were discovered several decades ago during the quest for low-dimensionality conductors (Giroult et al, 1981, 1982)
We can assume that the reported resistivity behaviour
The resistivity curves obtained for the P4W16O56 sample of is related to the ab conducting plane

Summary

Introduction

Monophosphate tungsten bronzes with pentagonal tunnels (MPTBp) were discovered several decades ago during the quest for low-dimensionality conductors (Giroult et al, 1981, 1982). Their structure is built from the regular intergrowth of PO4 tetrahedra slices and of ReO3-type slabs of corner-sharing octohedra WO6 giving rise to the formation of empty pentagonal tunnels at their junctions (Roussel et al, 2001). One strong interest of MPTBs arises from this possibility to investigate, within one system, the impact of dimensionality on electronic instabilities such as super-

Results

Discussion

Conclusion