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Novel electronic phase and device Physics in Topological Materials

Mardi 13 octobre 2015 13:30 - Duree : 1 heure
Lieu : LNCMI, salle de conférences "René Pauthenet" (bâtiment J, 2ème étage) - 25 rue des martyrs - 38000 Grenoble

Orateur : Wei-Li LEE (Institute of Physics, Academia Sinica Taipei, Taïwan)

Electronic band structure dictates the physical property in a material, where the electronic density of states and effective mass of electrons can be deduced and provide direct explanation to many experimental observations. In a recent development, non‐trivial topology in a bulk band turns out to lead to new electronic phases that are fundamentally different from any known phases. Several representative phenomena will be presented. First is the demonstration of field‐effect thermoelectricity in a dual‐gated bilayer‐graphene (BLG), where a perpendicular electric field on a BLG breaks the inversion symmetry and thus gives rise to the opening of a band gap. Such a large tuning of band structure by pure electric field is very unusual and open up a new route for device physics. Secondly, the zero‐magnetic‐field quantum anomalous Hall effect (QAHE) will be demonstrated in a magnetic topological insulator. The Dirac surface states will form dissipationless one‐dimensional chiral edge channel along the Dirac mass domain walls, which in turn results in the quantization of the Hall resistance. Unlike typical quantum Hall system, there is no need for a large external magnetic field in QAHE. A non‐trivial bulk band topology is mainly responsible for the appearance of such an unusual QAHE phase. At last, we will present the observation of large transverse current in Cd3As2 Dirac semimetal system. The large transverse Hall‐like signal derives from the large Berry curvature effect (anomalous velocity term) in three‐dimensional Rashba‐like spin splitted bands that can be obtained by including the Cd antisite defects in the band calculations. Such intrinsic anomalous velocity contribution in the transport equation can be quite common in topological Dirac/Weyl semimetal systems.

Reference :

1. Chang-Ran Wang, Wen-Sen Lu, Lei Hao, Wei-Li Lee, Ting-Kuo Lee, Feng Lin, I-Chun Cheng, and Jian-Zhang Chen, “Enhanced Thermoelectric Power in Dual-Gated Bilayer Graphene”, PHYSICAL REVIEW LETTERS, 107, 186602 (2011).

2. Xufeng Kou, Shih-Ting Guo, Yabin Fan, Lei Pan, Murong Lang, Ying Jiang, Qiming Shao, Tianxiao Nie, Koichi Murata, Jianshi Tang, Yong Wang, Liang He, Ting-Kuo Lee, Wei-Li Lee, and Kang L. Wang , 2014, “Scale-Invariant Quantum Anomalous Hall Effect in Magnetic Topological Insulators beyond the Two-Dimensional Limit”, PHYSICAL REVIEW LETTERS, 113, 137201 (2014).

3. Xufeng Kou, Lei Pan, Jing Wang, Yabin Fan, Eun Sang Choi, Wei-Li Lee, Tianxiao Nie, Koichi Murata, Qiming Shao, Shou-Cheng Zhang, and Kang L. Wang, “Metal-to-Insulator Switching in Quantum Anomalous Hall States”, NATURE COMMUNICATIONS (2015), accepted.

4. Shih-Ting Guo, R. Sankar, Yung-Yu Chien, Tay-Rong Chang, Horng-Tay Jeng, Guang-Yu Guo, F. C. Chou, and Wei-Li Lee, “Large Transverse Current in Topological Dirac Semimetal Cd3As2”, (2015) submitted.

Contact : anne-laure.barra@lncmi.cnrs.fr

Discipline évènement : (Physique)
Entité organisatrice : (LNCMI)
Nature évènement : (Séminaire)
Evènement répétitif : (Séminaire LNCMI)
Site de l'évènement : Polygone scientifique

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