Dependence of quantum timescales on symmetry

The role of time in quantum mechanics and the timescale associated with quantum transitions remains an open question in physics, especially on an experimental level. Here we use an experimental method based on spin- and angle-resolved photoemission spectroscopy from spin-degenerate dispersive states to determine the Eisenbud-Wigner-Smith time delay of photoemission. This timescale of the quantum transition is measured for materials with different dimensionality and correlation strength. A direct link is found between the dimensionality, or rather the symmetry, of the system and the attosecond timescale of the quantum transition. The quasi 2-dimensional transition metal dichalcogenides 1T-TiSe 2 and 1T-TiTe 2 show timescales around 150 as, whereas in quasi 1-dimensional CuTe, the transition takes more than 200 as. This is in stark contrast with the 26 as obtained for 3-dimensional pure Cu. These results provide new insights into the role of symmetry in quantum timescales and may provide a route to understanding the role of time in quantum mechanics.