04. Mai 2023

Vortrag M. Sc. Hicham Nimoh Vortrag M. Sc. Hicham Nimoh

AC-Kolloquium am 04.05.2023: "2D-Metals with locked charge density wave, in the novel layered monophosphate tungsten bronzes [Ba(PO4)2]WmO3m-3"

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Hicham Nimoh1, 2*, Robert Glaum2, Andrés Cano3, Angel M. Arévalo-López1, Olivier Mentré1

1 UCCS (Unité de Catalyse et Chimie du Solide), Université de Lille, Centrale Lille/ENSCL,59000, Lille, France;

2 Institut für Anorganische Chemie, Rheinische Friedrich-Wilhelms Universität Bonn,
Gerhard-Domagk-Str. 1 53121 Bonn, Germany;

3 Institut NEEL CNRS/UGA UPR2940, 25 rue des Martyrs, BP 166, 38042, Grenoble, France

* hicham.nimoh.etu@univ-lille.fr


Keywords: phosphate-bronze, 2D metal, Charge-Density-Wave, layered structure, Hidden FS nesting

We have synthesized a whole novel structural branch of mixed-valent, layered barium tungsten monophosphate bronzes (so-called L-MPTB*) with the general formula [Ba(PO4)2][WmO3m-3] (m = 3 (W5.33+), 4 (W5.50+), and 5 (W5.60+)). The structures are build from spacer-layers [Ba(PO4)2]4‒ and separating ReO3-like layers of variable thickness (Fig. 1). The spacers guarantee a “genuine” 2D-behavior, and enforce an overall trigonal structure preserved down to 1.8 K for the whole series. The L-MPTB* display some analogies but also major differences in comparison to the long.known MPTBs. From a structural point of view, our L-MPTB* correspond to the scission of the well-known  hexagonal tungsten phosphate bronzes (MPTBh’s) into the trigonal-oxide layers (Fig. 1). The L-MPTB* show steady 2D-metallic behavior and no anomaly in their heat capacity/thermopower down to 1.8 K. This is in contrast with the other tungsten bronzes of the literature [1] which systematically develop Charge Density Wave (CDW) instabilities with significant W-shifts or low-T superconductivity (Fig. 1). However, they hold the whole set of ingredients to develop CDW in terms of their tungsten valence and 2D-Fermi surfaces (Fig. 1) thus prompting for hidden nesting. This novel structural family with “locked CDW” opens wide perspectives in the field of correlated metals.

Figure 1: Structural analogy between a) K1.3P4W8O32 [2] and b) L-MPTB* (m = 3) with ideal resistivities. c) m = 4 d) m = 5 e) m = 3 Fermi surface

[1] M. Greenblatt, Acc. Chem. Res. 29, 219-228 (1996). [2] M. Dusek, J. Luedecke, S. van Smaalen, J. Mater. Chem. 12, 1408-1414 (2002).

Figure 1: Structural analogy
Figure 1: Structural analogy © Hicham Nimoh, Robert Glaum, Andrés Cano, Angel M. Arévalo-López, Olivier Mentré
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