Tuning a Schottky barrier in a photoexcited topological insulator with transient Dirac cone electron-hole asymmetry

Hajlaoui, Mahdi; Papalazarou, E.; Mauchain, Julien; Perfetti, L.; Taleb‐Ibrahimi, A.; Navarin, Fabien; Monteverde, M.; Auban‐Senzier, Pascale; Pasquier, Claude; Moisan, Nicolas; Boschetto, D.; Neupane, Madhab; Hasan, M. Zahid; Durakiewicz, Tomasz; Jiang, Zhigang; Yang, Xu; Miotkowski, I.; Chen, Yong P.; Jia, Shuang; Ji, Huiwen; Cava, R. J.; Marsi, M.

doi:10.1038/ncomms4003

Cited by 110 publications

(130 citation statements)

References 38 publications

(67 reference statements)

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“…Experiments were performed on Bi 2 Se 3 thin-films of 6,8,10,12,15,20,25,30,35, and 40 quintuple layers (QL ~ 1 nm) thick using a Ti:Sapphire laser with pulse duration 100 fs, center photon energy 1.51 eV (820 nm) and repetition rate 80 MHz. The films were grown on 0.5 mm Al 2 O 3 (0001) substrates by molecular beam epitaxy, with a 10 nm thick MgF 2 capping layer to protect against oxidation.…”

Section: Sample and Experimental Setupmentioning

confidence: 99%

“…1,2 However, because surface effects can be easily masked by three-dimensional (3D) free carriers of the insulating medium (bandgap of bulk Bi 2 Se 3 ~0.3 eV), [3][4][5][6][7][8][9][10] the control of purely Dirac-SS-governed properties of TIs remains a topic of interest. The problem can be partially solved by using the compensation doping method or a backgate voltage technique, 11,12 which efficiently deplete 3D carriers and hence switch electronic properties of the material to those related to 2D Dirac SS.…”

Section: Introductionmentioning

confidence: 99%

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Acoustic phonon dynamics in thin-films of the topological insulator Bi₂Se₃

Glinka

Babakiray

Johnson

et al. 2015

Journal of Applied Physics

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Transient reflectivity traces measured for nanometer-sized films (6 -40 nm) of the topological insulator Bi 2 Se 3 revealed GHz-range oscillations driven within the relaxation of hot carriers photoexcited with ultrashort (~100 fs) laser pulses of 1.51 eV photon energy. These oscillations have been suggested to result from acoustic phonon dynamics, including coherent longitudinal acoustic phonons in the form of standing acoustic waves. An increase of oscillation frequency from ~35 to ~70 GHz with decreasing film thickness from 40 to 15 nm was attributed to the interplay between two different regimes employing traveling-acoustic-waves for films thicker than 40 nm and the film bulk acoustic wave resonator (FBAWR) modes for films thinner than 40 nm. The amplitude of oscillations decays rapidly for films below 15 nm thick when the indirect intersurface coupling in Bi 2 Se 3 films switches the FBAWR regime to that of the Lamb wave excitation. The frequency range of coherent longitudinal acoustic phonons is in good agreement with elastic properties of Bi 2 Se 3 .

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Section: Sample and Experimental Setupmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Acoustic phonon dynamics in thin-films of the topological insulator Bi₂Se₃

Glinka

Babakiray

Johnson

et al. 2015

Journal of Applied Physics

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“…Once the dressing field of the pump pulse disappears (t > 500 fs), the sidebands disappear, leaving a heated Dirac cone. The dynamics of this non-equilibrium heated distribution of electrons has been discussed in a number of Tr-ARPES experiments [25][26][27][28] . Here we will focus on the Tr-ARPES spectra taken at t = 0 to ascertain the relative contribution of Floquet-Bloch and Volkov states.…”

mentioning

confidence: 99%

Selective scattering between Floquet–Bloch and Volkov states in a topological insulator

Mahmood¹,

Chan²,

Alpichshev³

et al. 2016

Nature Phys

320

273

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The coherent optical manipulation of solids is emerging as a promising way to engineer novel quantum states of matter 1-5 . The strong time-periodic potential of intense laser light can be used to generate hybrid photon-electron states. Interaction of light with Bloch states leads to Floquet-Bloch states, which are essential in realizing new photo-induced quantum phases [6][7][8] . Similarly, dressing of free-electron states near the surface of a solid generates Volkov states, which are used to study nonlinear optics in atoms and semiconductors 9 . The interaction of these two dynamic states with each other remains an open experimental problem. Here we use time-and angle-resolved photoemission spectroscopy (Tr-ARPES) to selectively study the transition between these two states on the surface of the topological insulator Bi 2 Se 3 . We find that the coupling between the two strongly depends on the electron momentum, providing a route to enhance or inhibit it. Moreover, by controlling the light polarization we can negate Volkov states to generate pure Floquet-Bloch states. This work establishes a systematic path for the coherent manipulation of solids via light-matter interaction.The manipulation of solids using ultrafast optical pulses has opened up a new paradigm in condensed matter physics by allowing the study of emergent physical properties that are otherwise inaccessible in equilibrium 1,2,10 . An important example is provided by the Floquet-Bloch states 11 , which emerge in solids owing to a coherent interaction between Bloch states inside the solid and a periodic driving potential. This is a consequence of the Floquet theorem 12 , which states that a Hamiltonian periodic in time with period T has eigenstates that are evenly spaced by the drive energy (2π/T ). Floquet-Bloch states have generated a lot of interest recently both for realizing exotic states of matter such as a Floquet Chern insulator 7 , as well as understanding non-equilibrium periodic thermodynamics 13,14 . Experimental observation of these states requires the measurement of the transient electronic band structure of a crystal as it is perturbed by light. As has recently been demonstrated 15 in the topological insulator Bi 2 Se 3 , time-and angleresolved photoemission spectroscopy (Tr-ARPES) is a key tool that can achieve this. Characteristic signatures of Floquet-Bloch states in the Tr-ARPES spectra include replicas of the original band structure that are separated by the driving photon energy 15 .In addition to Floquet-Bloch states, light can also generate other coherent phenomena in solids [16][17][18] . In particular, it can dress freeelectron states near the surface of a solid (Fig. 1a), as the surface can provide the momentum conservation necessary for a photon to interact with a free electron. This dressing was first observed in time-resolved photoemission experiments 17 and has subsequently been referred to as laser-assisted photoemission (LAPE). LAPE is typically understood [19][20][21] by invoking the Volkov solution, which is an e...

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“…Therefore these materials provide an exciting avenue to engineer the topological states, which is a crucial requisite for realizing different quantum phenomena and spintronics applications. In perspective, further ultrafast ARPES experiments [41][42][43][44][45], possibly with spin resolution, are needed to investigate the dynamics of the topological states, information of fundamental interest with important practical implications. From a methodological standpoint, the combination of ARPES and 2PPE measurements is a promising tool to explore the critical (un)occupied states in other materials.…”

mentioning

confidence: 99%

Engineering the topological surface states in the(Sb2)m−Sb2Te3(m=0
Johannsen
¹
,
Autès
²
,
Crepaldi
³

et al. 2015
Phys. Rev. B
20
1
20
0
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We investigate the evolution of both the occupied and unoccupied electronic structure in representative compounds of the infinitely adaptive superlattice series (Sb 2 ) m -Sb 2 Te 3 (m = 0-3) by means of angle-resolved photoemission spectroscopy and time-delayed two-photon photoemission, combined with first-principles band-structure calculations. We discover that the topological nature of the surface states and their spin texture are robust, with dispersions evolving from linear (Dirac-like) to parabolic (Rashba-like) along the series, as the materials evolve from semiconductors to semimetals. Our findings provide a promising strategy for engineering the topological states with the desired flexibility needed for realizing different quantum phenomena and spintronics applications. Three-dimensional topological insulators (TIs) are materials where the topological properties of the insulating bulk band structure guarantee the existence of metallic surface states [1,2]. These topological surface states (TSS) are characterized by a Dirac-like energy-momentum dispersion and by a helical spin-momentum texture [3,4] that protects them against backscattering and localization [5,6]. TIs are promising materials for spintronics and provide an exceptional playground to study novel physical phenomena [7,8]. Possible applications depend on the ability to control the electronic properties of the TSS. Common strategies for achieving such a control involve chemical substitution and adsorbate doping [9][10][11][12][13]. Alternatively, it has been proposed that multilayer heterostructures could be used to obtain artificial TIs with tunable properties defined by the stacking sequences of the constituent two-dimensional building blocks [14][15][16].In this Rapid Communication, we demonstrate the possibility of TSS band-structure engineering in the naturally occurring homologous series of topological superlattices (Sb 2 ) m -(Sb 2 Te 3 ) n composed of Sb 2 bilayers (BLs) and Sb 2 Te 3 quintuple layers (QLs) [17,18]. This series enables a systematic investigation of the evolution of topological properties as a function of the stacking sequence of the constituent building blocks. Our results show that the topological states are remarkably robust and that their dispersion can be tuned in the explored range (m = 0-3; n = 1), and in bulk Sb, with an unchanging strong Z 2 index ν 0 = 1.All (Sb 2 ) m -(Sb 2 Te 3 ) n compounds display layered crystal structures produced by ordered stacking of Sb 2 Te 3 QLs and antimony BLs along the c axis of the hexagonal unit cell. This provides for an "infinitely adaptive series" of * marco.grioni@epfl.ch distinct compounds between the end member compositions Sb 2 Te 3 (m = 0) and Sb (n = 0) [17][18][19][20] that are known to be a TI and a topological semimetal, respectively [21][22][23][24][25][26][27]. Early experiments assessed the topological nature of bulk Sb and Sb-Bi alloys [21,22]. By contrast, the experimental observation of the predicted TSS in Sb 2 Te 3 has been delayed by the intrinsic p doping ...

show abstract

Tuning a Schottky barrier in a photoexcited topological insulator with transient Dirac cone electron-hole asymmetry

Cited by 110 publications

References 38 publications

Acoustic phonon dynamics in thin-films of the topological insulator Bi₂Se₃

Acoustic phonon dynamics in thin-films of the topological insulator Bi₂Se₃

Selective scattering between Floquet–Bloch and Volkov states in a topological insulator

Engineering the topological surface states in the(Sb2)m−Sb2Te3(m=0
Johannsen
¹
,
Autès
²
,
Crepaldi
³

et al. 2015
Phys. Rev. B
20
1
20
0
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Tuning a Schottky barrier in a photoexcited topological insulator with transient Dirac cone electron-hole asymmetry

Cited by 110 publications

References 38 publications

Acoustic phonon dynamics in thin-films of the topological insulator Bi2Se3

Acoustic phonon dynamics in thin-films of the topological insulator Bi2Se3

Selective scattering between Floquet–Bloch and Volkov states in a topological insulator

Engineering the topological surface states in the(Sb2)m−Sb2Te3(m=0Johannsen1, Autès2, Crepaldi3 et al. 2015Phys. Rev. B201200View full textAdd to dashboardCite

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Acoustic phonon dynamics in thin-films of the topological insulator Bi₂Se₃

Acoustic phonon dynamics in thin-films of the topological insulator Bi₂Se₃

Engineering the topological surface states in the(Sb2)m−Sb2Te3(m=0
Johannsen
¹
,
Autès
²
,
Crepaldi
³

et al. 2015
Phys. Rev. B
20
1
20
0
View full text Add to dashboard Cite