Precursor region with full phonon softening above the charge-density-wave phase transition in 2H-TaSe2

Xingchen Shen; Rolf Heid; Roland Hott; Amir-Abbas Haghighirad; Björn Salzmann; Marli Dos Reis Cantarino; Claude Monney; Ayman H Said; Mehdi Frachet; Bridget Murphy; Kai Rossnagel; Stephan Rosenkranz; Frank Weber

doi:10.1038/s41467-023-43094-5

Precursor region with full phonon softening above the charge-density-wave phase transition in 2H-TaSe₂

Nat Commun. 2023 Nov 10;14(1):7282. doi: 10.1038/s41467-023-43094-5.

Authors

Xingchen Shen^{1

2}, Rolf Heid¹, Roland Hott¹, Amir-Abbas Haghighirad¹, Björn Salzmann³, Marli Dos Reis Cantarino^{3

4}, Claude Monney³, Ayman H Said⁵, Mehdi Frachet¹, Bridget Murphy^{6

7}, Kai Rossnagel^{6

7

8}, Stephan Rosenkranz⁹, Frank Weber¹⁰

Affiliations

¹ Institute for Quantum Materials and Technologies, Karlsruhe Institute of Technology, 76021, Karlsruhe, Germany.
² College of Physics, Chongqing University, Chongqing, 401331, P. R. China.
³ Département de Physique and Fribourg Center for Nanomaterials, Université de Fribourg, 1700, Fribourg, Switzerland.
⁴ Instituto de Física, Universidade de São Paulo, São Paulo, São Paulo, 05508-090, Brazil.
⁵ Advanced Photon Source, Argonne National Laboratory, Lemont, IL, 60439, USA.
⁶ Institute of Experimental and Applied Physics and KiNSIS, Kiel University, 24098, Kiel, Germany.
⁷ Ruprecht Haensel Laboratory, Kiel University, 24098, Kiel, Germany.
⁸ Ruprecht Haensel Laboratory, Deutsches Elektronen-Synchrotron DESY, 22607, Hamburg, Germany.
⁹ Materials Science Division, Argonne National Laboratory, Lemont, IL, 60439, USA.
¹⁰ Institute for Quantum Materials and Technologies, Karlsruhe Institute of Technology, 76021, Karlsruhe, Germany. [email protected].

Abstract

Research on charge-density-wave (CDW) ordered transition-metal dichalcogenides continues to unravel new states of quantum matter correlated to the intertwined lattice and electronic degrees of freedom. Here, we report an inelastic x-ray scattering investigation of the lattice dynamics of the canonical CDW compound 2H-TaSe₂ complemented by angle-resolved photoemission spectroscopy and density functional perturbation theory. Our results rule out the formation of a central-peak without full phonon softening for the CDW transition in 2H-TaSe₂ and provide evidence for a novel precursor region above the CDW transition temperature T_CDW, which is characterized by an overdamped phonon mode and not detectable in our photoemission experiments. Thus, 2H-TaSe₂ exhibits structural before electronic static order and emphasizes the important lattice contribution to CDW transitions. Our ab-initio calculations explain the interplay of electron-phonon coupling and Fermi surface topology triggering the CDW phase transition and predict that the CDW soft phonon mode promotes emergent superconductivity near the pressure-driven CDW quantum critical point.