Your present position: HOME > News & Events > BIT News

New progress made by BIT on photothermoelectric effect of topological insulators

release date :2015-01-08 11:21:00  |   [ close window ]ViewCount:
Translator: News Agency of BIT
Editor: News Center of BIT  Zhao Lin

    Recently, an article entitled “Topological Surface State Enhanced Photothermoelectric Effect in Bi2Se3 Nanoribbons” have been published on Nano Letters (DOI: 10.1021/nl501276e, 4389, 2014) and aroused attention in the profession. The article was written by a research group studying the photothermoelectric effect of topological insulators, with the participation of researcher Wu Hanchun, from School of Physics of BIT (Beijing Institute of Technology). The international research group contained the research group from Yu Dapeng’s nanostructure and low dimensional physics laboratory of Peking University, professor Dong Sun from international center for quantum materials of Peking University, professor Zhou Shuyun from School of Physics of Tsinghua University (in charge of AEPES measurement) and professor G.V. Tendeloo and doctor Ke Xiaoxing from University of Antwerp, Belgium. They finished the innovative research on photothermoelectric effect together. The topic is about the research of physical characteristics of new materials and how to apply these to create spin-polarized current.

    Spintronics is a branch of the subject studying characteristics of the electron intrinsic spin. It is likely to be widely applied in diverse fields. The successful commercialization to read heads of modern hard drives marked the earliest application of the research. It also has a promising future in many fields, like magnetoresistive random-access memory and spin-LED. Besides, ESR (electron spin resonance) technology is also widely used in solid state physics, chemistry and biomedical fields.

    Usually, creating spin-polarized current is crucial to the application of spintronics. These years, the research on how to create spin-polarized current has been highly recognized in the region of physics. The study on physical characteristics of new materials is an innovative way, among which the topological insulator is one of the key materials. The topological insulator is a new quantum state, that behaves as an insulator in its interior but whose surface contains conducting states. It has an extraordinary spinning and magnetoelectric characteristics. The topological insulator offers a new potential way to create spin-polarized current.

    The research group where researcher Wu is in aims to study the properties of Bi2Se3 (Bismuth selenide), a significant three-dimensional topological insulator. Bi2Se3 is stable, easy to produce and energetic. That is why it is so popular in the research nowadays. Moreover, Bi2Se3 is also a great heat conducting material. Under the inhomogeneous optical radiation, Bi2Se3 shows photo-thermal effects.

    With this characteristic, we can control the molecular structure on the surface of topological insulators and quantify them. Because of the insulation state in the interior, the molecular structure on the surface completely depends on the exterior molecule. The controllability of its basic structure enables us to analyze the state of spinning electron and create spin-polarized current. The study is scientifically valuable and has a great developing prospect.

    With the idea in mind, the research group utilized CVD (chemical vapor deposition) technology and made nanobelts and nanosheets of Bi2Se3. CVD can be a method to produce solid materials. With the CVD technology, chemical reactions take place when substances are gaseous. Then solid substances are formed on the heating surface of the raw materials.

    After we produced the materials for experiments, we selected a cross-section sample, and observed its surface characteristics. We clearly saw a QL layer along the [100] axis and the basic unit of –Se-Bi-Se-Bi-Se-. We also saw the surface state of Bi2Se3 through ARPES.

    The influenced of linear polarized light, left polarized light and right polarized light towards the photothermoelectric effect of topological insulators Bi2Se3.

    With the Aharonov–Bohm effect (proving the electromagnetic potential vector can be directly measured) and Shubnikov-de Haas effect (an oscillation in the conductivity of a material that occurs at low temperatures in the presence of very intense magnetic fields), we measured the traits of Dirac fermion particles (particles that satisfy the Dirac Fermion equation, the spinning parameter should be 1/2, 3/2...) on the surface of the topological insulators. We used CPL (circular-polarized light) to selectively activate certain electron on the surface of Bi2Se3 and created spin-polarized surface state. Due to the fixed relation between spinning direction and momentum direction, the sample would create a fixed-direction photoelectric current. We also observed the enhanced photothermoelectric effect of CPL in Bi2Se3 sample. The experiment results can be expected to provide a new way to create spin-polarized current, boosting the application of spintronics in our daily lives.
Sina Microblog
Tencent Microblog
Share: WeChat (Remark:Need to be shared through mobile phones and other mobile devices)