Recent theories and experiments have suggested that strong spin-orbit
coupling effects in certain band insulators can give rise to a new phase of
quantum matter, the so-called topological insulator, which can show macroscopic
entanglement effects. Such systems feature two-dimensional surface states whose
electrodynamic properties are described not by the conventional Maxwell
equations but rather by an attached axion field, originally proposed to
describe strongly interacting particles. It has been proposed that a
topological insulator with a single spin-textured Dirac cone interfaced with a
superconductor can form the most elementary unit for performing fault-tolerant
quantum computation. Here we present an angle-resolved photoemission
spectroscopy study and first-principle theoretical calculation-predictions that
reveal the first observation of such a topological state of matter featuring a
single-surface-Dirac-cone realized in the naturally occurring Bi$_2$Se$_3$
class of materials. Our results, supported by our theoretical predictions and
calculations, demonstrate that undoped compound of this class of materials can
serve as the parent matrix compound for the long-sought topological device
where in-plane surface carrier transport would have a purely quantum
topological origin. Our study further suggests that the undoped compound
reached via n-to-p doping should show topological transport phenomena even at
room temperature.Comment: 3 Figures, 18 pages, Submitted to NATURE PHYSICS in December 200

A. Bansil

A. Pal

AK Geim

D Hsieh

D. Grauer

D. Hsieh

D. Qian

E Mooser

F Wilczek

FJ DiSalvo

GR Hyde

H. Lin

J Black

JE Moore

JP Perdew

L Fu

L. Wray

M Franz

M Hoesch

M Konig

M. Z. Hasan

P Blaha

P Larson

R. J. Cava

RWG Wyckoff

S Hufner

S LaShell

S-C Zhang

SK Mishra

VA Greanya

X-L Qi

Y. S. Hor

Y. Xia

English

arXiv

Recent experiments and theories have suggested that strong spin-orbit coupling effects in certain band insulators can give rise to a new phase of quantum matter, the so-called topological insulator, which can show macroscopic quantum-entanglement effects. Such systems feature two-dimensional surface states whose electrodynamic properties are described not by the conventional Maxwell equations but rather by an attached axion field, originally proposed to describe interacting quarks. It has been proposed that a topological insulator with a single Dirac cone interfaced with a superconductor can form the most elementary unit for performing fault-tolerant quantum computation. Here we present an angle-resolved photoemission spectroscopy study that reveals the first observation of such a topological state of matter featuring a single surface Dirac cone realized in the naturally occurring Bi2 Se3 class of materials. Our results, supported by our theoretical calculations, demonstrate that undoped Bi2 Se3 can serve as the parent matrix compound for the long-sought topological device where in-plane carrier transport would have a purely quantum topological origin. Our study further suggests that the undoped compound reached via n-to-p doping should show topological transport phenomena even at room temperature

Xia, Yuqi

Qian, Dong

Hsieh, David

Wray, Lewis Andrew

Pal, Arijeet

Lin, Hsin

Bansil, Arun

Grauer, David C.

Hor, Yew San

Cava, Robert Joseph

Hasan, Md Zahid

Missouri University of Science and Technology (Missouri S&T): Scholars' Mine

Observation of a Large-Gap Topological-Insulator Class with a Single Dirac Cone on the Surface

Recent experiments and theories have suggested that strong spin–orbit coupling effects in certain band insulators can give rise to a new phase of quantum matter, the so-called topological insulator, which can show macroscopic quantum-entanglement effects. Such systems feature two-dimensional surface states whose electrodynamic properties are described not by the conventional Maxwell equations but rather by an attached axion field, originally proposed to describe interacting quarks. It has been proposed that a topological insulator with a single Dirac cone interfaced with a superconductor can form the most elementary unit for performing fault-tolerant quantum computation. Here we present an angle-resolved photoemission spectroscopy study that reveals the first observation of such a topological state of matter featuring a single surface Dirac cone realized in the naturally occurring Bi2Se3 class of materials. Our results, supported by our theoretical calculations, demonstrate that undoped Bi2Se3 can serve as the parent matrix compound for the long-sought topological device where in-plane carrier transport would have a purely quantum topological origin. Our study further suggests that the undoped compound reached via n-to-p doping should show topological transport phenomena even at room temperature

Xia, Y

Qian, D

Hsieh, D

Wray, L

Pal, A

Lin, H

Bansil, A

Grauer, D

Hor, YS

Cava, RJ

Hasan, MZ

UCL Discovery

Observation of a large-gap topological-insulator class with a single Dirac cone on the surface

Recent experiments and theories have suggested that strong spin–orbit coupling effects in certain band insulators can give rise to a new phase of quantum matter, the so-called topological insulator, which can show macroscopic quantum-entanglement effects. Such systems feature two-dimensional surface states whose electrodynamic properties are described not by the conventional Maxwell equations but rather by an attached axion field, originally proposed to describe interacting quarks. It has been proposed that a topological insulator with a single Dirac cone interfaced with a superconductor can form the most elementary unit for performing fault-tolerant quantum computation. Here we present an angle-resolved photoemission spectroscopy study that reveals the first observation of such a topological state of matter featuring a single surface Dirac cone realized in the naturally occurring Bi_2Se_3 class of materials. Our results, supported by our theoretical calculations, demonstrate that undoped Bi_2Se_3 can serve as the parent matrix compound for the long-sought topological device where in-plane carrier transport would have a purely quantum topological origin. Our study further suggests that the undoped compound reached via n-to-p doping should show topological transport phenomena even at room temperature

Xia, Y.

Qian, D.

Hsieh, D.

Wray, L.

Pal, A.

Lin, H.

Bansil, A.

Grauer, D.

Hor, Y. S.

Cava, R. J.

Hasan, M. Z.

Caltech Authors - Main

SUPPLEMENTARY INFORMATION
doi: 10.1038/nPHYS1274
nature PHYSicS | www.nature.com/naturephysics 1
 [Supplementary Information] A large-gap topological 
insulator matrix with a single surface Dirac cone
Y. Xia, D. Qian, D. Hsieh, L. Wray, A. Pal,  H. Lin, A. Bansil, D. Grauer,  Y. S. Hor,
R. J. Cava and M. Z. Hasan 
Topic: Confirming the calculated valence and surface band structure by 
comparison with experimental ARPES data over a wider energy range
The calculated valence band dispersion is in good correspondence while making a 
comparison with the experimental data taken in both the M−Γ  and K−Γ  directions 
(Fig. S1). The first and twelfth quintuple blocks are taken as the surfaces of the slab. The 
fraction of electron charge residing in the atomic spheres of these two surface blocks are 
presented by the color of the bands. Bright lines indicate bands located inside the bulk 
sample. These bands should overlap with a bulk energy band at a particular kz value, after 
projected onto the 2D surface BZ. The calculation agrees with data after shifting the EF of 
the calculated result to 200 meV above the bottom of the lowest conduction band. Doping 
the semiconductor matrix with electrons allows one to study the connectivity of the 
surface and bulk states at all energies between the valence and conduction bands, thereby 
determining the unique and specific class of topological order of the parent materials [7]. 
In the measured spectra, the strongest quasiparticle signals are typically observed 
near normal electron emission, at around 1.5-2.0 eV. This band corresponds to a pure 
surface band lying outside the bulk projection of states. Strong quasiparticle signals near 
1
2 nature PHYSicS | www.nature.com/naturephysics
SUPPLEMENTARY INFORMATION doi: 10.1038/nPHYS1274
Γ  are of surface origin, based on their direct correspondence with the band calculation.
Our energy dependent study of the bands suggests insignificant kz dependence of these 
states, confirming the 2D (surface) nature of the bands.
Fig S1: Experimental band dispersions are compared with theoretical calculations. The band
second-derivative images and first-principles calculation results along M−Γ  (a) and
K−Γ directions (b) are presented. The color of the calculated bands represents the fraction of 
electronic charge residing in the surface layers. A rigid shift of EF is included to match the lowest 
energy excitations in the ARPES data with calculations, a consequence of the system being 
somewhat electron-doped. The strongest signals are observed from the surface states.
We would like to note that the calculated bandwidth is smaller than the measured 
values. A better agreement requires a renormalization of the theoretical results by a self-
energy ),(''),('),( EkiEkEk
rrr Σ+Σ=Σ . A similar adjustment of ab initio results to match
2
nature PHYSicS | www.nature.com/naturephysics 3
SUPPLEMENTARY INFORMATIONdoi: 10.1038/nPHYS1274
Γ  are of surface origin, based on their direct correspondence with the band calculation.
Our energy dependent study of the bands suggests insignificant kz dependence of these 
states, confirming the 2D (surface) nature of the bands.
Fig S1: Experimental band dispersions are compared with theoretical calculations. The band
second-derivative images and first-principles calculation results along M−Γ  (a) and
K−Γ directions (b) are presented. The color of the calculated bands represents the fraction of 
electronic charge residing in the surface layers. A rigid shift of EF is included to match the lowest 
energy excitations in the ARPES data with calculations, a consequence of the system being 
somewhat electron-doped. The strongest signals are observed from the surface states.
We would like to note that the calculated bandwidth is smaller than the measured 
values. A better agreement requires a renormalization of the theoretical results by a self-
energy ),(''),('),( EkiEkEk
rrr Σ+Σ=Σ . A similar adjustment of ab initio results to match
2
experimental band data was used for graphite. It is believed that the underestimation of 
quasiparticle bandwidths by LDA is due to its failure to account for many body effects in 
describing the excited final states. Approximating ),(' Ek
rΣ by a linear function 
stretches the band dispersion [31]. For Bi2Se3, an approximately 30% stretch is required 
to match the lowest energy excitations to theory.
[31] Heske, C. et al. Band widening in graphite. Phys. Rev. B 59, 4680 (1999). 
3


Crossref

https://authors.library.caltech.edu/49668/7/nphys1274-s1.pdf