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TT: Fachverband Tiefe Temperaturen

TT 48: 2D Materials: Electronic structure, excitations, etc. II (joint session O/HL/TT)

TT 48.5: Vortrag

Mittwoch, 11. März 2026, 11:30–11:45, TRE/MATH

Long-living metastable electronic states in substituted 1T-TaS₂ — •Gaël Reecht¹, Jesumony Jayabalan¹, Ričards Knipšis², Florian Diekmann³, Friedemann Queisser², Ping Zhou¹, Walter Schnelle⁴, Kai Rossnagel^3,5, Ralf Schützhold², Manuel Gruber¹, and Uwe Bovensiepen¹ — ¹University Duisburg-Essen, Germany — ²HZ Dresden-Rossendorf, Germany — ³CAU of Kiel, Germany — ⁴MPI for Chemical Physics of Solids, Dresden, Germany — ⁵DESY, Hamburg, Germany

1T-TaS₂ is a prototypical correlated material whose low-temperature phase exhibits a commensurate charge density wave forming Star-of-David (SOD) clusters. Each SOD hosts a single electron close to E_F and, due to strong on-site Coulomb repulsion, the system enters a Mott insulating state. Adding or removing an electron creates doublon or holon excitations, which typically relax within few femtoseconds [1]. Here, we manipulate the lifetime of the quasiparticle excitations by substituting some Ta with an electron richer element. Using LT-scanning tunnelling microscopy and spectroscopy (STM/STS) and time-resolved photoemission spectroscopy, we observe metastable doublons with lifetimes ranging from fs to hours. STM/STS further shows that these excitations are locally confined. The experimental observations are corroborated by a theoretical description based on a Fermi-Hubbard model. The disorder induced by the random substitution leads to a spatial localization of holon and doublon wavefunctions at the origin of the long lifetimes observed experimentally.

[1] M. Ligges et al., Phys. Rev. Lett., 120, 166401 (2018)

Keywords: Scanning Tunneling Microscopy; Strongly Correlated Materials