Abstract
Time- and angle-resolved photoemission spectroscopy (TR-ARPES) provides access to the ultrafast evolution of electrons and many-body interactions in solid-state systems. However, the momentum- and energy-resolved transient photoemission intensity may not be unambiguously described by the intrinsic relaxation dynamics of photoexcited electrons alone. The interpretation of the time-dependent photoemission signal can be affected by the transient evolution of the electronic distribution, and both the one-electron removal spectral function as well as the photoemission matrix elements. Here we investigate the topological insulator Bi1.1Sb0.9Te2S to demonstrate, by means of a detailed probe-polarization dependent study, the transient contribution of matrix elements to TR-ARPES.
Highlights
The development of pump-probe techniques has provided the opportunity to extend the study of solid state systems into the time domain, garnering important insights regarding transient phenomena in addition to new perspectives on persistent challenges from equilibrium [1]
The multi-layer and -orbital structure of the wavefunction of the topological surface state (TSS) leads to a characteristic angular modulation of the photoemission intensity, as a consequence of the interference between photoelectrons emitted from different layers and orbitals [29,30,31,32,33,34]13
We mapped the dispersion of the bulk conduction band via TR-ARPES along the G –Mdirection by introducing the 1.55 eV pump excitation (see figure 1(d))
Summary
The development of pump-probe techniques has provided the opportunity to extend the study of solid state systems into the time domain, garnering important insights regarding transient phenomena in addition to new perspectives on persistent challenges from equilibrium [1]. The momentum information accessible to time- and angle-resolved photoemission spectroscopy (TR-ARPES) offers a significant advantage over other pump-probe techniques, as the modifications to the electronic structure and relaxation dynamics of photoexcited electrons are observed directly. TR-ARPES has been widely used to study the transient evolution of exotic phases in condensed matter as disparate as unconventional superconductivity [2,3,4], charge-order [5], excitonic condensates [6], and Floquet states [7, 8]. It is conventional to emphasize the temporal evolution of the electronic temperature [4, 9,10,11,12] or the photoemission intensity in well-defined momentum-energy regions [13,14,15,16]
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