Ultrafast time-resolved differential reflectivity of Bi2Se3 crystals is studied using optical pump-probe spectroscopy. Three distinct relaxation processes are found to contribute to the initial transient reflectivity changes. The deduced relaxation timescale and the sign of the reflectivity change suggest that electron–phonon interactions and defect-induced charge trapping are the underlying mechanisms for the three processes. After the crystal is exposed to air, the relative strength of these processes is altered and becomes strongly dependent on the excitation photon energy.

1.
For a recent review, see
X. -L.
Qi
and
S. -C.
Zhang
, arXiv:1008.2026 (unpublished).
2.
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
,
Nat. Phys.
5
,
398
(
2009
).
3.
H.
Zhang
,
C. -X.
Liu
,
X. -L.
Qi
,
X.
Dai
,
Z.
Fang
, and
S. -C.
Zhang
,
Nat. Phys.
5
,
438
(
2009
).
4.
Y. S.
Hor
,
A.
Richardella
,
P.
Roushan
,
Y.
Xia
,
J. G.
Checkelsky
,
A.
Yazdani
,
M. Z.
Hasan
,
N. P.
Ong
, and
R. J.
Cava
,
Phys. Rev. B
79
,
195208
(
2009
).
5.
A. D.
LaForge
,
A.
Frenzel
,
B. C.
Pursley
,
T.
Lin
,
X.
Liu
,
J.
Shi
, and
D. N.
Basov
,
Phys. Rev. B
81
,
125120
(
2010
).
6.
N. P.
Butch
,
K.
Kirshenbaum
,
P.
Syers
,
A. B.
Sushkov
,
G. S.
Jenkins
,
H. D.
Drew
, and
J.
Paglione
,
Phys. Rev. B
81
,
241301
(R) (
2010
).
7.
J. G.
Analytis
,
R. D.
McDonald
,
S. C.
Riggs
,
J. -H.
Chu
,
G. S.
Boebinger
, and
I. R.
Fisher
, arXiv:1003.1713 (unpublished).
8.
J.
Chen
,
H. J.
Qin
,
F.
Yang
,
J.
Liu
,
T.
Guan
,
F. M.
Qu
,
G. H.
Zhang
,
J. R.
Shi
,
X. C.
Xie
,
C. L.
Yang
,
K. H.
Wu
,
Y. Q.
Li
, and
L.
Lu
,
Phys. Rev. Lett.
105
,
176602
(
2010
).
9.
H.
Steinberg
,
D. R.
Gardner
,
Y. S.
Lee
, and
P.
Jarillo-Herrero
, arXiv:1003.3137 (unpublished).
10.
J. G.
Checkelsky
,
Y. S.
Hor
,
R. J.
Cava
, and
N. P.
Ong
, arXiv:1003.3883 (unpublished).
11.
J.
Shah
,
Ultrafast Spectroscopy of Semiconductors and Semiconductor Nanostructures
(
Springer
,
Berlin
,
1999
).
12.
J.
Qi
,
J. A.
Yan
,
H.
Park
,
A.
Steigerwald
,
Y.
Xu
,
S. N.
Gilbert
,
X.
Liu
,
J. K.
Furdyna
,
S. T.
Pantelides
, and
N.
Tolk
,
Phys. Rev. B
81
,
115208
(
2010
), and references therein.
13.
A. Q.
Wu
,
X.
Xu
, and
R.
Venkatasubramanian
,
Appl. Phys. Lett.
92
,
011108
(
2008
).
14.
W.
Richter
,
H.
Köhler
, and
C. R.
Becker
,
Phys. Status Solidi B
84
,
619
(
1977
).
15.
S.
Rast
,
M. L.
Schneider
,
M.
Onellion
,
X. H.
Zeng
,
W.
Si
,
X. X.
Xi
,
M.
Abrecht
,
D.
Ariosa
,
D.
Pavuna
,
Y. H.
Ren
,
G.
Lüpke
, and
I.
Perakis
,
Phys. Rev. B
64
,
214505
(
2001
).
16.
Y.
Xu
,
M.
Khafizov
,
L.
Satrapinsky
,
P.
Kus
,
A.
Plecenik
, and
R.
Sobolewski
,
Phys. Rev. Lett.
91
,
197004
(
2003
).
17.
18.
T.
Taneda
,
G. P.
Pepe
,
L.
Parlato
,
A. A.
Golubov
, and
R.
Sobolewski
,
Phys. Rev. B
75
,
174507
(
2007
).
19.
J.
Demsar
,
V. K.
Thorsmølle
,
J. L.
Sarrao
, and
A. J.
Taylor
,
Phys. Rev. Lett.
96
,
037401
(
2006
).
20.
S.
Gupta
,
M. Y.
Frankel
,
J. A.
Valdmanis
,
J. F.
Whitaker
,
G. A.
Mourou
,
F. W.
Smith
, and
A. R.
Calawa
,
Appl. Phys. Lett.
59
,
3276
(
1991
).
21.
J. G.
Wang
,
C. J.
Sun
,
Y.
Hashimoto
,
J.
Kono
,
G. A.
Khodaparast
,
Ł.
Cywiński
,
L. J.
Sham
,
G. D.
Sanders
,
C. J.
Stanton
, and
H.
Munekata
,
J. Phys.: Condens. Matter
18
,
R501
(
2006
).
22.
T.
Dekorsy
,
G. C.
Cho
, and
H.
Kurz
,
Light Scattering in Solids VIII: Fullerenes, Semiconductor Surfaces, Coherent Phonons
,
Topics in Applied Physics
Vol.
76
(
Springer
,
Berlin
,
2000
).
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