Intrinsic and extrinsic effects on the electrostatic field at the surface of Bi2Se3

Xu, Chao; Hewitt, Andrew; Wang, Jingying; Guan, Tianshuai; Boltersdorf, Jonathan; Maggard, Paul A.; Dougherty, Daniel B.; Gündoğdu, Kenan

doi:10.1063/1.4891719

Cited by 6 publications

(6 citation statements)

References 48 publications

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“…We modify the Bi 2 Se 3 surface by cleaving, which is known to trigger transport processes on a time scale of 100 min. 6,10 Extensive studies on such Bi 2 Se 3 aging effects 20,21,41,42 revealed two mechanisms (see schematic of Fig. 2b): (1) formation of an electric-dipole layer due to charge transfer from adsorbates 21,42 or surface lattice relaxation 19 and (2) migration of bulk defects, mainly Se vacancies, toward the surface.…”

Section: Resultsmentioning

confidence: 99%

“…2b): (1) formation of an electric-dipole layer due to charge transfer from adsorbates 21,42 or surface lattice relaxation 19 and (2) migration of bulk defects, mainly Se vacancies, toward the surface. 21,41 While the surface dipole layer is very localized (thickness of ∼ 3 nm), 21 the redistribution of bulk Se vacancies induces a more extended space-charge region (thickness of tens of nanometers). 21,41 We now relate these processes to the amplitude evolution of J yz and J x following sample cleaving (Fig.…”

Section: Resultsmentioning

confidence: 99%

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Ultrafast photocurrents at the surface of the three-dimensional topological insulator Bi2Se3

Braun¹,

Mußler²,

Hruban³

et al. 2016

Nat Commun

189

176

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Three-dimensional topological insulators are fascinating materials with insulating bulk yet metallic surfaces that host highly mobile charge carriers with locked spin and momentum. Remarkably, surface currents with tunable direction and magnitude can be launched with tailored light beams. To better understand the underlying mechanisms, the current dynamics need to be resolved on the timescale of elementary scattering events (∼10 fs). Here, we excite and measure photocurrents in the model topological insulator Bi2Se3 with a time resolution of 20 fs by sampling the concomitantly emitted broadband terahertz (THz) electromagnetic field from 0.3 to 40 THz. Strikingly, the surface current response is dominated by an ultrafast charge transfer along the Se–Bi bonds. In contrast, photon-helicity-dependent photocurrents are found to be orders of magnitude smaller than expected from generation scenarios based on asymmetric depopulation of the Dirac cone. Our findings are of direct relevance for broadband optoelectronic devices based on topological-insulator surface currents.

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Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

Ultrafast photocurrents at the surface of the three-dimensional topological insulator Bi2Se3

Braun¹,

Mußler²,

Hruban³

et al. 2016

Nat Commun

189

176

View full text Add to dashboard Cite

show abstract

“…1(c)], however, a non-negligible bulk contribution can arise from electric-field induced nonlinear susceptibility in the SCR. 11,12,16,17 The SCR is formed by accumulation of Se vacancies upon exposed to air. 12,[15][16][17] Because the interface between Bi 2 Se 3 and BaF 2 has only little amount of vacancies or defects, 22 we neglect the SCR effect near that interface.…”

Section: For Transmitted Sh Beam (2 ) Generated By a Polarization Shementioning

confidence: 99%

“…10 In the presence of a DC field, however, the field-induced second-order nonlinearity in the bulk can be significant. 11,12 This is often the case if a space charge region (SCR) exists in the bulk, for example, near the interface of a semiconductor due to band bending. For the topological insulator, Bi 2 Se 3 , near the air/Bi 2 Se 3 interface, Se vacancies tend to migrate from the bulk and accumulate at the interface; the resulting excessive amount of positive surface charges leads to the formation of SCR.…”

Section: Introductionmentioning

confidence: 99%

Surface and bulk contributions to the second-harmonic generation in Bi2Se3

Shi

Yao

et al. 2016

Phys. Rev. B

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Second harmonic generation (SHG) from three-dimensional topological insulators originates from both surface and bulk, which does not allow probing of surface states unless the measurement can separate the two contributions. In this study, we used combined measurements of transmitted and reflected SHG from epitaxially grown Bi 2 Se 3 thin films of different thickness on BaF 2 , and a bulk Bi 2 Se 3 crystal, to deduce surface and bulk nonlinear susceptibilities of Bi 2 Se 3 separately. We found that the surface * E-mail: yrshen@berkeley.edu, wtliu@fudan.edu.cn 2 contribution to SHG was comparable to that from the bulk of the crystal, but becomes dominant in ultrathin films. In the latter case, contributions from both air/Bi 2 Se 3 and Bi 2 Se 3 /BaF 2 interfaces were significant, and exhibited a strong out-of-plane polar ordering. The bulk contribution came mainly from the space charge region (SCR), which was formed by Se vacancies aggregated at the air/Bi 2 Se 3 interface; its magnitude can provide an estimate on the field strength in the SCR. Clarification of surface and bulk contributions to SHG can help nonlinear optical techniques be used as a versatile in situ probe for topological insulators.3

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“…Second generation topological insulator (TI) materials such as Bi 2 Te 3 , Bi 2 Se 3 and Sb 2 Te 3 with common structural characteristics of gapped insulating bulks and metallic conducting surfaces have gained great attention in recent years 1 2 3 4 5 . TI surfaces exhibit the linear Dirac spectrum dispersion, resulting in a unique electronic property 6 ; however, optical properties and applications require further exploration. Since Bernard et al initially identified Bi 2 Te 3 as an effective saturable absorber in 2012 7 ; the application values of TIs in nonlinear photonics have received enhanced research interests.…”

mentioning

confidence: 99%

PVP-Assisted Solvothermal Synthesis of High-Yielded Bi2Te3 Hexagonal Nanoplates: Application in Passively Q-Switched Fiber Laser

Zhang

Lin

et al. 2015

Sci Rep

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High-yielded Bi2Te3 hexagonal nanoplates were fabricated via a facile solvothermal method with the assistance of poly (vinyl pyrrolidone) (PVP). Effects of PVP molecular weight and concentration on the morphology and size distribution of the products were illustrated in this study. Molecular weight of PVP is significant for determining the morphology of Bi2Te3. The hexagonal nanoplates with high yield were obtained in the presence of PVP with molecular weight of 40000–45000. The average size and size distribution of Bi2Te3 nanoplates can be slightly varied by controlling concentration of PVP. High-yielded Bi2Te3 nanoplates exhibit characteristics of saturable absorption, identified by open-aperture Z-scan technique. The synthesized Bi2Te3 nanoplates with large saturation intensity of 4.6 GW/cm2 and high modulation depth of 45.95% generated a stable passively Q-switched fiber laser pulse at 1.5 μm. In comparison with recently reported Q-switched fiber lasers utilizing exfoliated Bi2Te3 nanosheets, our passive Q-switching operations could be conducted at a relatively low threshold power of 30.2 mW or a quite high output power of 99.45 mW by tuning the cavity parameters.

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Intrinsic and extrinsic effects on the electrostatic field at the surface of Bi2Se3

Cited by 6 publications

References 48 publications

Ultrafast photocurrents at the surface of the three-dimensional topological insulator Bi2Se3

Ultrafast photocurrents at the surface of the three-dimensional topological insulator Bi2Se3

Surface and bulk contributions to the second-harmonic generation in Bi2Se3

PVP-Assisted Solvothermal Synthesis of High-Yielded Bi2Te3 Hexagonal Nanoplates: Application in Passively Q-Switched Fiber Laser

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