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Ultrafast electron dynamics at the Dirac node of the topological insulator Sb2Te3.

Zhu S, Ishida Y, Kuroda K, Sumida K, Ye M, Wang J, Pan H, Taniguchi M, Qiao S, Shin S, Kimura A - Sci Rep (2015)

Bottom Line: Sb2Te3 has an in-gap DP located completely above the Fermi energy (EF).The excited electrons in the upper Dirac cone stay longer than those below the DP to form an inverted population.This was attributed to a reduced density of states (DOS) near the DP.

View Article: PubMed Central - PubMed

Affiliation: Graduate School of Science, Hiroshima University, 1-3-1 Kagamiyama, Higashi-Hiroshima, Hiroshima 739-8526, Japan.

ABSTRACT
Topological insulators (TIs) are a new quantum state of matter. Their surfaces and interfaces act as a topological boundary to generate massless Dirac fermions with spin-helical textures. Investigation of fermion dynamics near the Dirac point (DP) is crucial for the future development of spintronic devices incorporating topological insulators. However, research so far has been unsatisfactory because of a substantial overlap with the bulk valence band and a lack of a completely unoccupied DP. Here, we explore the surface Dirac fermion dynamics in the TI Sb2Te3 by time- and angle-resolved photoemission spectroscopy (TrARPES). Sb2Te3 has an in-gap DP located completely above the Fermi energy (EF). The excited electrons in the upper Dirac cone stay longer than those below the DP to form an inverted population. This was attributed to a reduced density of states (DOS) near the DP.

No MeSH data available.


Related in: MedlinePlus

Schematics of the pump and decay processes.The state before pumping (a), upon the pump (b), subsequent decay (c) leading to an hourglass-shaped electron distribution (d), and the final state (e). The colour gradation represents the electron density.
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f3: Schematics of the pump and decay processes.The state before pumping (a), upon the pump (b), subsequent decay (c) leading to an hourglass-shaped electron distribution (d), and the final state (e). The colour gradation represents the electron density.

Mentions: Schematics of the pump and decay processes from the state before pumping to the final state are shown in Fig. 3. As shown in Fig. 3(b), the direct photo-excitation from the occupied to the unoccupied states is accompanied by the impact ionization. During the decay [Fig. 3(c)], the flow of electrons from high to low energy is bottlenecked near the DP to result in the hourglass-shaped electron distribution shown in Fig. 3(d).


Ultrafast electron dynamics at the Dirac node of the topological insulator Sb2Te3.

Zhu S, Ishida Y, Kuroda K, Sumida K, Ye M, Wang J, Pan H, Taniguchi M, Qiao S, Shin S, Kimura A - Sci Rep (2015)

Schematics of the pump and decay processes.The state before pumping (a), upon the pump (b), subsequent decay (c) leading to an hourglass-shaped electron distribution (d), and the final state (e). The colour gradation represents the electron density.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4543953&req=5

f3: Schematics of the pump and decay processes.The state before pumping (a), upon the pump (b), subsequent decay (c) leading to an hourglass-shaped electron distribution (d), and the final state (e). The colour gradation represents the electron density.
Mentions: Schematics of the pump and decay processes from the state before pumping to the final state are shown in Fig. 3. As shown in Fig. 3(b), the direct photo-excitation from the occupied to the unoccupied states is accompanied by the impact ionization. During the decay [Fig. 3(c)], the flow of electrons from high to low energy is bottlenecked near the DP to result in the hourglass-shaped electron distribution shown in Fig. 3(d).

Bottom Line: Sb2Te3 has an in-gap DP located completely above the Fermi energy (EF).The excited electrons in the upper Dirac cone stay longer than those below the DP to form an inverted population.This was attributed to a reduced density of states (DOS) near the DP.

View Article: PubMed Central - PubMed

Affiliation: Graduate School of Science, Hiroshima University, 1-3-1 Kagamiyama, Higashi-Hiroshima, Hiroshima 739-8526, Japan.

ABSTRACT
Topological insulators (TIs) are a new quantum state of matter. Their surfaces and interfaces act as a topological boundary to generate massless Dirac fermions with spin-helical textures. Investigation of fermion dynamics near the Dirac point (DP) is crucial for the future development of spintronic devices incorporating topological insulators. However, research so far has been unsatisfactory because of a substantial overlap with the bulk valence band and a lack of a completely unoccupied DP. Here, we explore the surface Dirac fermion dynamics in the TI Sb2Te3 by time- and angle-resolved photoemission spectroscopy (TrARPES). Sb2Te3 has an in-gap DP located completely above the Fermi energy (EF). The excited electrons in the upper Dirac cone stay longer than those below the DP to form an inverted population. This was attributed to a reduced density of states (DOS) near the DP.

No MeSH data available.


Related in: MedlinePlus