Surface State Dynamics of Topological Insulators Investigated by Femtosecond Time- and Angle-Resolved Photoemission Spectroscopy

Hedayat, Hamoon; Bugini, Davide; Yi, Hemian; Chen, Chao‐Yu; Zhou, Xianju; Cerullo, Giulio; Dallera, C.; Carpene, E.

doi:10.3390/app8050694

Cited by 6 publications

(4 citation statements)

References 36 publications

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“…This behaviour can be explained by intra-band scattering of electrons towards states with lower energy, resulting in a a build-up at the bottom of the bands. This accumulation of electrons is attributed to the modest electron-phonon coupling 56 – 58 and to the lack of states/scattering channels for electron and hole recombination in an intrinsic TI 20 , 59 – 61 . Despite the similar rise-times of TSS and B2 , the decay occurs on significantly different time scales of ps and ps, respectively.…”

Section: Resultsmentioning

confidence: 99%

Ultrafast evolution of bulk, surface and surface resonance states in photoexcited $$\hbox {Bi}_{2}\hbox {Te}_{3}$$

Hedayat¹,

Bugini²,

Yi³

et al. 2021

Sci Rep

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We use circular dichroism (CD) in time- and angle-resolved photoemission spectroscopy (trARPES) to measure the femtosecond charge dynamics in the topological insulator (TI) $$\hbox {Bi}_{2}\hbox {Te}_{3}$$ Bi 2 Te 3 . We detect clear CD signatures from topological surface states (TSS) and surface resonance (SR) states. In time-resolved measurements, independently from the pump polarization or intensity, the CD shows a dynamics which provides access to the unexplored electronic evolution in unoccupied states of $$\hbox {Bi}_{2}\hbox {Te}_{3}$$ Bi 2 Te 3 . In particular, we are able to disentangle the unpolarized electron dynamics in the bulk states from the spin-textured TSS and SR states on the femtosecond timescale. Our study demonstrates that photoexcitation mainly involves the bulk states and is followed by sub-picosecond transport to the surface. This provides essential details on intra- and interband scattering in the relaxation process of TSS and SR states. Our results reveal the significant role of SRs in the subtle ultrafast interaction between bulk and surface states of TIs.

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Section: Resultsmentioning

confidence: 99%

Ultrafast evolution of bulk, surface and surface resonance states in photoexcited $$\hbox {Bi}_{2}\hbox {Te}_{3}$$

Hedayat¹,

Bugini²,

Yi³

et al. 2021

Sci Rep

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“…Momentum-sensitive techniques can clarify the microscopic mechanisms by resolving specific electron states and their interactions with other degrees of freedom. Indeed, TR-ARPES has been effectively exploited to study the evolution of order parameters in different complex systems [32][33][34]. In contrast to TRR, the technique of TR-ARPES probes the electronic band structure in the reciprocal space enabling one to focus on a specific region of interest e.g.…”

Section: Introductionmentioning

confidence: 99%

Investigation of the non-equilibrium state of strongly correlated materials by complementary ultrafast spectroscopy techniques

et al. 2021

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Photoinduced non-thermal phase transitions are new paradigms of exotic non-equilibrium physics of strongly correlated materials. An ultrashort optical pulse can drive the system to a new order through complex microscopic interactions that do not occur in the equilibrium state. Ultrafast spectroscopies are unique tools to reveal the underlying mechanisms of such transitions which lead to transient phases of matter. Yet, their individual specificities often do not provide an exhaustive picture of the physical problem. One effective solution to enhance their performance is the integration of different ultrafast techniques. This provides an opportunity to simultaneously probe physical phenomena from different perspectives while maintaining the same experimental conditions. In this context, we performed complementary experiments by combining time-resolved reflectivity and time and angle-resolved photoemission spectroscopy. We demonstrate the advantage of this combined approach by investigating the complex charge density wave (CDW) phase in 1T-TiSe 2 . Specifically, we show the key role of lattice degrees of freedom to establish and stabilize the CDW in this material.

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“…First, a broad spectral probing of the magneto-optical response would give a deeper understanding of the interactions between the charge, lattice and magnetic sectors. Further, it would be interesting to study the electronic and lattice dynamics at low temperatures and long delays more directly by complementary time-resolved techniques [70], like timeresolved ARPES [71], XRD [72], Raman [73], etc. These studies will reveal the intrinsic time scales and interactions of holons and doublons and other quasiparticles and could answer whether a transient lattice deformation can quench magnetic exchange interactions, while simultaneously enhancing the anisotropic Kitaev interactions to drive α-RuCl 3 into the Kitaev spin liquid state.…”

Section: Discussionmentioning

confidence: 99%

Nonequilibrium dynamics of $α$-RuCl$_{3}$ -- a time-resolved magneto-optical spectroscopy study

Wagner¹,

Sahasrabudhe²,

Versteeg³

et al. 2022

Preprint

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We present time-resolved magneto-optical spectroscopy on the magnetic Mott-Hubbard-insulating Kitaev spin liquid candidate α-RuCl3 to investigate the nonequilibrium dynamics of its antiferromagnetically ordered zigzag groundstate after photoexcitation. A systematic study of the transient magnetic linear dichroism under different experimental conditions (temperature, external magnetic field, photoexcitation density) gives direct access to the dynamical interplay of charge excitations with the zigzag ordered state on ultrashort time scales. We observe a rather slow initial demagnetization (few to 10s of ps) followed by a long-lived non-thermal antiferromagnetic spin-disordered state (100−1000s of ps), which can be understood in terms of holons and doublons disordering the antiferromagnetic background after photoexcitation. Varying temperature and fluence in the presence of an external magnetic field reveals two distinct photoinduced dynamics associated with the zigzag and quantum paramagnetic disordered phases. The photo-induced non-thermal spindisordered state shows universal compressed-exponential recovery dynamics related to the growth and propagation of zigzag domains on nanosecond time scales, which is interpreted within the framework of the Fatuzzo-Labrune model for magnetization reversal. The study of nonequilibrium states in strongly correlated materials is a relatively unexplored topic, but our results are expected to be extendable to a large class of Mott-Hubbard insulator materials with strong spin-orbit coupling.

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Surface State Dynamics of Topological Insulators Investigated by Femtosecond Time- and Angle-Resolved Photoemission Spectroscopy

Cited by 6 publications

References 36 publications

Ultrafast evolution of bulk, surface and surface resonance states in photoexcited $$\hbox {Bi}_{2}\hbox {Te}_{3}$$

Ultrafast evolution of bulk, surface and surface resonance states in photoexcited $$\hbox {Bi}_{2}\hbox {Te}_{3}$$

Investigation of the non-equilibrium state of strongly correlated materials by complementary ultrafast spectroscopy techniques

Nonequilibrium dynamics of $α$-RuCl$_{3}$ -- a time-resolved magneto-optical spectroscopy study

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