Ultrafast Electron Dynamics in the Topological Insulator Bi2Se3 Studied by Time-Resolved Photoemission Spectroscopy

Abstract

We characterize the topological insulator Bi${}_2$Se${}_3$ using time- and angle- resolved photoemission spectroscopy. By employing two-photon photoemission, a complete picture of the unoccupied electronic structure from the Fermi level up to the vacuum level is obtained. We demonstrate that the unoccupied states host a second, Dirac surface state which can be resonantly excited by 1.5 eV photons. We then study the ultrafast relaxation processes following optical excitation. We find that they culminate in a persistent non-equilibrium population of the first Dirac surface state, which is maintained by a meta-stable population of the bulk conduction band. Finally, we perform a temperature-dependent study of the electron-phonon scattering processes in the conduction band, and find the unexpected result that their rates decrease with increasing sample temperature. We develop a model of phonon emission and absorption from a population of electrons, and show that this counter-intuitive trend is the natural consequence of fundamental electron-phonon scattering processes. This analysis serves as an important reminder that the decay rates extracted by time-resolved photoemission are not in general equal to single electron scattering rates, but include contributions from filling and emptying processes from a continuum of states.

In Press: Journal of Electron Spectroscopy & Related Phenomena (special issue on 2-photon photoemission spectroscopy)

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Cited by in corpus (31)

• Angle-resolved photoemission spectroscopy and its application to topological materials
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• Time- and Angle-Resolved Photoemission Studies of Quantum Materials
• Distinguishing bulk and surface electron-phonon coupling in the topological insulator Bi2Se3 using time-resolved photoemission spectroscopy
• Direct determination of mode-projected electron-phonon coupling in the time-domain
• Band resolved imaging of photocurrent in a topological insulator
• Unraveling photoinduced spin dynamics in topological insulator Bi2Se3
• Ultrafast spin polarization control of Dirac fermions in topological insulators
• Momentum resolved spin dynamics of bulk and surface excited states in the topological insulator $\mathrm{B}{\mathrm{i}}_2\mathrm{S}{\mathrm{e}}_3$
• Enhanced electron-phonon coupling in graphene with periodically distorted lattice
• Effect of dynamical spectral weight redistribution on effective interactions in time-resolved spectroscopy
• Measurement of Topological Order based on Metric-Curvature Correspondence
• Theoretical Understanding of Photon Spectroscopies in Correlated Materials In and Out of Equilibrium
• Optical manipulation of Rashba-split 2-Dimensional Electron Gas
• Advancing time- and angle-resolved photoemission spectroscopy: The role of ultrafast laser development
• Establishing non-thermal regimes in pump-probe electron-relaxation dynamics
• Impact of ultrafast transport on the high-energy states of a photoexcited topological insulator
• Nonequilibrium Electron Dynamics In Pump-Probe Spectroscopy: Role Of Excited Phonon Populations
• Role of matrix elements in the time-resolved photoemission signal
• Nonequilibrium Electron Dynamics in a Solid with a Changing Nodal Excitation Gap
• What do the two times in two-time correlation functions mean for interpreting tr-ARPES?
• Photocurrent measurements in topological insulator ${\text{Bi}}_2{\text{Se}}_3$ nanowires
• Impact ionization dynamics in small band-gap 2D materials from a coherent phonon mechanism
• Nanosecond dynamics in intrinsic topological insulator ${\text{Bi}}_{2-x}{\text{Sb}}_x{\text{Se}}_3$ revealed by time-resolved optical reflectivity
• Superconductivity induced by Ag intercalation in Dirac semimetal Bi${}_2$Se${}_3$
• Second harmonic generation and third harmonic generation in topological insulator-based van der Waals metamaterials
• Ultrafast electron dynamics at the Dirac node of the topological insulator Sb${}_2$Te${}_3$
• Optical amplification in a CDW-phase of a quasi-two dimensional material
• Control of intervalley scattering in Bi${}_2$Te${}_3$ via temperature-dependent band renormalization
• Band structure of Bi surfaces formed on Bi2Se3 upon exposure to air
• High repetition rate Time-Resolved VUV ARPES at 10.8 eV photon energy