Surface conduction of topological Dirac electrons in bulk insulating Bi2Se3

Kim, Dohun; Cho, Sungjae; Butch, Nicholas P.; Syers, Paul; Kirshenbaum, Kevin; Adam, Shaffique; Paglione, Johnpierre; Fuhrer, Michael S.

doi:10.1038/nphys2286

Cited by 363 publications

(405 citation statements)

References 30 publications

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“…1a, inset) consistent with gapless Dirac band structure of topological surface states 22 . As it was shown previously [22][23][24] , σ is linearly proportional to V g near V D suggesting that charged impurity scattering limits electronic transport for the present devices 22 . The observation of sublinear σ(V g ) at V g further away from V D may indicate that there are additional types of disorder, e.g.…”

supporting

confidence: 64%

“…Further tuning of carrier density is accomplished using a Si back gate and 300 nm SiO 2 gate dielectric. We showed previously [22] that in such thin Bi 2 Se 3 slabs in the TI regime that the top and bottom surfaces are strongly capacitively coupled through the high-dielectric-constant bulk (ε ~100 [20]) and couple nearly equally to the back gate. to negative voltage, reflected also in a shift to negative voltage of the zeroes in S. This thermal activation effect was explained by us in detail in a previous work [26].…”

mentioning

confidence: 97%

“…1b, inset) with typical aspect ratio (L/W) of about 2 and shortest length exceeding 2 µm using Ar plasma at a pressure of ~6.7 Pa (5 x 10 -2 Torr). Molecular charge transfer doping was done by thermal evaporation of ~10 nm of 2,3,5,6-tetrafluoro-7,7,8,8-tetracyanoquinodimethane organic molecules (SynQuest Labs) on top of the fabricated samples 22,33 .Measurement Thermopower measurement was done using Stanford Research Systems SR830Lock in amplifiers and a commercial cryostat equipped with 9 T superconducting magnet. Low frequency ac (ω < 17 Hz) heater currents was applied to the sample and the resultant 2ω thermoelectric voltage ΔV between two ends of thermisters (see Fig.…”

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confidence: 99%

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Ambipolar Surface State Thermoelectric Power of Topological Insulator Bi₂Se₃

et al. 2014

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We measure gate-tuned thermoelectric power of mechanically exfoliated Bi 2 Se 3 thin films in the topological insulator regime. The sign of the thermoelectric power changes across the charge neutrality point as the majority carrier type switches from electron to hole, consistent with the ambipolar electric field effect observed in conductivity and Hall effect measurements. Near charge neutrality point and at low temperatures, the gate dependent thermoelectric power follows the semiclassical Mott relation using the expected surface state density of states, but is larger than expected at high electron doping, possibly reflecting a large density of states in the bulk gap. The thermoelectric power factor shows significant enhancement near the electron-hole puddle carrier density ~ 0.5 x 10 12 cm -2 per surface at all temperatures. Together with the 2 expected reduction of lattice thermal conductivity in low dimensional structures, the results demonstrate that nanostructuring and Fermi level tuning of three dimensional topological insulators can be promising routes to realize efficient thermoelectric devices.KEYWORDS Topological Insulators, Thermoelectric Power, Ambipolar Electric Field Effect, Bismuth Selenide, Charge Transfer Doping.The efficiency of thermoelectric devices is determined by the thermoelectric figure of merit ZT = σS 2 T/κ, where S is thermoelectric power (Seebeck coefficient) and σ and κ are electrical and thermal conductivity respectively. For a given thermal conductivity (typically dominated by phonons) and temperature, ZT is determined by the electronic structure of a material through the power factor σS 2 . Nanostructuring has long been seen as a promising route to increase ZT both through decreasing κ via phonon boundary scattering, and increasing the power factor through confinement-induced band structure effects 1 . The discovery that important thermoelectric materials Bi 1-x Sb x and Bi 2 (Se,Te) 3 [2][3][4] are in fact 3D topological insulators (TI) has triggered new directions to improve ZT via nanostructuring. The 3D TIs have an insulating bulk but metallic surface states with spin-momentum helicity which cannot be localized by nonmagnetic disorder 4,5 . Recent theoretical calculations 6,7 show that significant enhancement of ZT is expected in 3D TIs particularly in thin film geometry where top and bottom surfaces can hybridize and form a surface gap 8 .Thermoelectric power is also of great interest in understanding the electronic transport properties of Dirac electronic systems 9 , thus measurement of the thermoelectric properties of TI surface states can elucidate details of the electronic structure of the ambipolar nature of 3 topological metallic surface states that cannot be probed by conductance measurements alone 10 .Although there have been theoretical investigations of thermal and thermoelectric properties of Dirac materials including graphene and TIs 6,7,[11][12][13][14][15] and thermoelectric transport in carbon nanotubes 16 and graphene 9,17-19 have been studied expe...

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confidence: 64%

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confidence: 97%

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Ambipolar Surface State Thermoelectric Power of Topological Insulator Bi₂Se₃

et al. 2014

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“…TI nanowires were obtained by mechanical exfoliation ('scotch tape method') of bulk (Bi 1.33 Sb 0.67 )Se 3 crystals on 300 nm SiO 2 /highly n-doped Si substrates 29 . The nanowires were identified via optical and atomic force microscopy 1,30,31 . Nanowire thickness was determined by atomic force microscopy, while the width was more accurately determined by scanning probe microscopy after all electrical measurements were completed.…”

Section: Methodsmentioning

confidence: 99%

“…I n three-dimensional topological insulator (3D TI) nanowires, charge transport occurs via gapless surface states where the spin is fixed perpendicular to the momentum [1][2][3][4][5][6] . When a magnetic field (B) is applied along the nanowire axis, the surface electrons encircling the wire pick up a phase of 2pF/F 0 , where F ¼ BS is the magnetic flux through cross-sectional area S and F 0 ¼ h/e is the magnetic flux quantum, where h is Planck's constant and e the electron charge.…”

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Aharonov–Bohm oscillations in a quasi-ballistic three-dimensional topological insulator nanowire

et al. 2015

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Aharonov-Bohm oscillations effectively demonstrate coherent, ballistic transport in mesoscopic rings and tubes. In three-dimensional topological insulator nanowires, they can be used to not only characterize surface states but also to test predictions of unique topological behaviour. Here we report measurements of Aharonov-Bohm oscillations in (Bi 1.33 Sb 0.67 )Se 3 that demonstrate salient features of topological nanowires. By fabricating quasi-ballistic three-dimensional topological insulator nanowire devices that are gate-tunable through the Dirac point, we are able to observe alternations of conductance maxima and minima with gate voltage. Near the Dirac point, we observe conductance minima for zero magnetic flux through the nanowire and corresponding maxima (having magnitudes of almost a conductance quantum) at magnetic flux equal to half a flux quantum; this is consistent with the presence of a low-energy topological mode. The observation of this mode is a necessary step towards utilizing topological properties at the nanoscale in post-CMOS applications.

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