Surface and interface states of Bi<sub>2</sub>Se<sub>3</sub> thin films investigated by optical second-harmonic generation and terahertz emission

Hamh, Sun Young; Park, S. H.; Jerng, Sahng‐Kyoon; Jeon, Jae Ho; Chun, Seung‐Hyun; Kahng, Se-Jong; Yu, Kwangnam; Choi, E. J.; Kim, Sanghoek; Choi, Suk‐Ho; Bansal, Namrata; Oh, Seongshik; Park, Joonbum; Kho, Byung Woo; Kim, Jun Sung; Lee, J. S.

doi:10.1063/1.4941420

Cited by 15 publications

(7 citation statements)

References 31 publications

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“…Finally, time-resolved techniques such as time-resolved ARPES, optical pump-optical probe spectroscopy with probe in the visible to mid-infrared range, time-resolved second harmonic generation (SHG), THz emission spectroscopy, as well as time-resolved THz spectroscopy (TRTS) have been used to uncover various aspects of optically excited carrier dynamics. ,− Of these techniques, optical pump-optical probe measurements are invaluable for probing interband processes, and time-resolved ARPES, time-resolved SHG and THz emission probe exclusively processes that occur at the surface. TRTS allows monitoring of the evolution of the complex optical conductivity in response to photoexcitation with subpicosecond time resolution, and is best suited for unraveling the dynamics of the photoexcited carriers as they interact with both the surface states and with the states in the bulk band structure.…”

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confidence: 99%

Photoexcited Free Carrier Dynamics in Bi₂Se₃, (Bi_0.75In_0.25)₂Se₃, and (Bi_0.50In_0.50)₂Se₃: From Topological to Band Insulator

et al. 2020

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Replacing some Bi with In in Bi 2 Se 3 transforms it from a topological insulator to a band insulator. Here, we have used time-resolved terahertz spectroscopy to investigate photoexcited carrier dynamics in (Bi 1−x In x ) 2 Se 3 films with indium concentration x = 0%, 25%, and 50%. In Bi 2 Se 3 , optically excited carriers scatter from the bulk conduction band states into high mobility topological surface states within picoseconds after excitation. We demonstrate that a second set of Dirac surface states, located ∼1.5−1.8 eV above the conduction band minimum and accessible to carriers excited by 3.1 eV pulses, is characterized by a higher mobility than the surface states within the band gap that dominate equilibrium conductivity. In (Bi 0.75 In 0.25 ) 2 Se 3 and (Bi 0.50 In 0.50 ) 2 Se 3 , which are insulating without photoexcitation, the dynamics of photoexcited free carriers are affected by the twin domain boundaries and are sensitive to the disorder introduced by indium substitution. Transient conductivity rise time, as well as the mobility and lifetime of the photoexcited carriers in (Bi 1−x In x ) 2 Se 3 films, can be tuned by the indium content, enabling tailoring of band insulators that have the desired optoelectronic properties and are fully structurally compatible with the topological insulator Bi 2 Se 3 for applications in high-speed photonic devices based on topological insulator/band insulator heterostructures.

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confidence: 99%

Photoexcited Free Carrier Dynamics in Bi₂Se₃, (Bi_0.75In_0.25)₂Se₃, and (Bi_0.50In_0.50)₂Se₃: From Topological to Band Insulator

et al. 2020

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“…Dirac and Weyl semimetals), which have common features characterized by some band(s) with linear dispersion in k-space near the Fermi level (Weng et al, 2016;Armitage et al, 2018). Owing to the exotic electronic structures in TMs, giant nonlinear responses can be usually expected, such as second harmonic generation (Wu et al, 2017;Patankar et al, 2018;Hamh et al, 2016), nonlinear Hall effect (Ma et al, 2019), and photogalvanic effect (PGE) (Guan et al, 2017;Li et al, 2017). Particularly, on the excitation of the femtosecond (fs) laser pulses, the ultrafast photocurrents and the associated electromagnetic wave emission in the terahertz (THz) regime have attracted enormous attention recently in TMs (Sirica et al, 2019;Gao et al, 2020;Rees et al, 2020;Ni et al, 2021;Braun et al, 2016).…”

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confidence: 99%

Terahertz wave emission from the trigonal layered PtBi2

et al. 2022

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“…[ 13 ] Very interestingly, pure 3D topological insulator (TI) combines the capabilities provided by its peculiar spin‐momentum locking and topologically protected electronic surface states, [ 26–30 ] have been demonstrated to successfully generate and flexibly manipulate the radiated elliptically polarized THz waves. [ 31–36 ] It has been proved that the interface between ferromagnetic metals and TIs played a significant role in the THz wave generation process. [ 37 ] However, the THz emission from pure TIs has been well studied in previous work, the THz efficiency was not that high compared with that based on SCC effect.…”

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confidence: 99%

Efficient Generation and Arbitrary Manipulation of Chiral Terahertz Waves Emitted from Bi₂Te₃–Fe Heterostructures

Chen

Wang

Chun

et al. 2021

Advanced Photonics Research

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Polarization arbitrary manipulated terahertz (THz) pulses with a prescribed amplitude temporal evolution and deposited electric‐field vectors can promote many disruptive technologies and enable enormous applications in polarization‐sensitive THz spectroscopy and imaging, ultrafast THz optospintronics, information encryption, and space exploration. However, the severe shortage of dynamically tunable THz polarization devices has impeded the proliferation of THz science and technology. Herein, a method of efficient generation and arbitrary manipulation of chiral THz waves in the topological insulator (TI)–iron (Fe) heterostructures through delicately engineering the linear photogalvanic effect (LPGE) and spin‐to‐charge conversion (SCC) effect induced by femtosecond laser pulses is proposed and demonstrated. Utilizing the intrinsic merits of optical‐controlled LPGE and magnetic field direction‐adjusted SCC effect, the TI–Fe can radiate chiral THz waves with arbitrarily tailored chirality and ellipticity. To verify the capability of such a novel chiral THz source, helical substructure associates THz circular dichroism spectroscopy is implemented on several (bio)materials, exemplified by the beetle exoskeletons. Furthermore, ultrafast switching between two THz chirality states can be realized by a double‐pulse excitation scheme. Such versatile chiral THz emitters with high efficiency and easy integration may have some disruptive applications.

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Surface and interface states of Bi₂Se₃ thin films investigated by optical second-harmonic generation and terahertz emission

Cited by 15 publications

References 31 publications

Photoexcited Free Carrier Dynamics in Bi₂Se₃, (Bi_0.75In_0.25)₂Se₃, and (Bi_0.50In_0.50)₂Se₃: From Topological to Band Insulator

Photoexcited Free Carrier Dynamics in Bi₂Se₃, (Bi_0.75In_0.25)₂Se₃, and (Bi_0.50In_0.50)₂Se₃: From Topological to Band Insulator

Terahertz wave emission from the trigonal layered PtBi2

Efficient Generation and Arbitrary Manipulation of Chiral Terahertz Waves Emitted from Bi₂Te₃–Fe Heterostructures

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Surface and interface states of Bi2Se3 thin films investigated by optical second-harmonic generation and terahertz emission

Cited by 15 publications

References 31 publications

Photoexcited Free Carrier Dynamics in Bi2Se3, (Bi0.75In0.25)2Se3, and (Bi0.50In0.50)2Se3: From Topological to Band Insulator

Photoexcited Free Carrier Dynamics in Bi2Se3, (Bi0.75In0.25)2Se3, and (Bi0.50In0.50)2Se3: From Topological to Band Insulator

Terahertz wave emission from the trigonal layered PtBi2

Efficient Generation and Arbitrary Manipulation of Chiral Terahertz Waves Emitted from Bi2Te3–Fe Heterostructures

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Surface and interface states of Bi₂Se₃ thin films investigated by optical second-harmonic generation and terahertz emission

Photoexcited Free Carrier Dynamics in Bi₂Se₃, (Bi_0.75In_0.25)₂Se₃, and (Bi_0.50In_0.50)₂Se₃: From Topological to Band Insulator

Photoexcited Free Carrier Dynamics in Bi₂Se₃, (Bi_0.75In_0.25)₂Se₃, and (Bi_0.50In_0.50)₂Se₃: From Topological to Band Insulator

Efficient Generation and Arbitrary Manipulation of Chiral Terahertz Waves Emitted from Bi₂Te₃–Fe Heterostructures