The spontaneous symmetry breaking in Ta 2 NiSe 5 is structural in nature

• DOI: 10.1073/pnas.2221688120
• Publication Date: 2023-04-18T17:48:15Z
• Authors: Edoardo Baldini; Alfred Zong; Dongsung Choi; Changmin Lee; Marios H. Michael; Lukas Windgaetter; Igor I. Mazin; Simone Latini; Doron Azoury; Baiqing Lv; Anshul Kogar; Yifan Su; Yao Wang; Yangfan Lu; Tomohiro Takayama; Hidenori Takagi; Andrew J. Millis; Angel Rubio; Eugene Demler; Nuh Gedik

The excitonic insulator is an electronically driven phase of matter that emerges upon the spontaneous formation and Bose condensation excitons. Detecting this exotic order in candidate materials a subject paramount importance, as size gap band structure establishes potential collective state for superfluid energy transport. However, identification real solids hindered by coexistence structural parameter with same symmetry order. Only few are currently believed to host dominant phase, Ta 2 NiSe 5 being most promising. Here, we test scenario using ultrashort laser pulse quench broken-symmetry transition metal chalcogenide. Tracking dynamics material’s electronic crystal after light excitation reveals spectroscopic fingerprints compatible only primary phononic nature. We rationalize our findings through state-of-the-art calculations, confirming accounts opening. Our results suggest breaking mostly character, hampering possibility realize quasi-dissipationless