Picosecond Competing Dynamics of Apparent Semiconducting-Metallic Phase Transition in the Topological Insulator Bi2Se3

被引:20
作者
Sim, Sangwan [3 ]
Lee, Seungmin [4 ]
Moon, Jisoo [5 ]
In, Chihun [1 ,2 ,3 ]
Lee, Jekwan [2 ,3 ]
Noh, Minji [2 ,3 ]
Kim, Jehyun [2 ]
Jang, Woosun [6 ]
Cha, Soonyoung [7 ]
Seo, Seung Young [8 ]
Oh, Seongshik [5 ]
Kim, Dohun [1 ]
Soon, Aloysius [6 ]
Jo, Moon-Ho [7 ,8 ]
Choi, Hyunyong [1 ,2 ]
机构
[1] Seoul Natl Univ, Dept Phys & Astron, Seoul 08826, South Korea
[2] Seoul Natl Univ, Inst Appl Phys, Seoul 08826, South Korea
[3] Hanyang Univ, Div Elect Engn, Ansan 15588, South Korea
[4] Yonsei Univ, Sch Elect & Elect & Engn, Seoul 120749, South Korea
[5] Rutgers State Univ, Dept Phys & Astron, Piscataway, NJ 08854 USA
[6] Yonsei Univ, Dept Mat Sci & Engn, Seoul 03722, South Korea
[7] Inst for Basic Sci Korea, Ctr Artificial Low Dimens Elect Syst, Pohang 37673, South Korea
[8] Pohang Univ Sci & Technol POSTECH, Dept Mat Sci & Engn, Pohang 37673, South Korea
基金
美国国家科学基金会; 新加坡国家研究基金会;
关键词
topological insulator; ultrafast spectroscopy; terahertz spectroscopy; apparent phase transition; PHONON INTERACTION; THZ GENERATION; CONVERSION;
D O I
10.1021/acsphotonics.9b01603
中图分类号
TB3 [工程材料学];
学科分类号
0805 ; 080502 ;
摘要
Resolving the complex interplay between surface and bulk response is a long-standing issue in the topological insulators (TIs). Some studies have reported surface-dominated metallic responses, yet others show semiconducting-like bulk photoconductance. Using ultrafast terahertz spectroscopy with the advent of Fermi-level engineered TIs, we discovered that such difference arises from the time-dependent competing process of two parameters, namely, the Dirac-carrier surface scattering rate and the bulk Drude weight. After infrared femtosecond pulse excitation, we observed a metal-like photoconductance reduction for the prototypical n-type Bi2Se3 and a semiconductor-like increased photoconductance for the p-type Bi2Se3. Surprisingly, the bulkinsulating Bi2Se3, which is presumably similar to graphene, exhibits a semiconducting-to-metallic phase apparent transition at 10 ps. The sign-reversed, yet long-lasting (>= 500 ps) metallic photoconductance was observed only in the bulk-insulating Bi2Se3, indicating that such dynamic phase transition is governed by the time-dependent competing interplay between the surface scattering rate and the bulk Drude weight. Our observations illustrate new photophysical phenomena of the photoexcited-phase transition in TIs and demonstrate entirely distinct dynamics compared to graphene and conventional gapped semiconductors.
引用
收藏
页码:759 / 764
页数:6
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