Ya Feng
Chinese Academy of Sciences
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Publication
Featured researches published by Ya Feng.
Proceedings of the National Academy of Sciences of the United States of America | 2012
Chaoyu Chen; Shaolong He; Hongming Weng; Wentao Zhang; Lin Zhao; Haiyun Liu; Xiaowen Jia; Daixiang Mou; Shanyu Liu; Junfeng He; Yingying Peng; Ya Feng; Zhuojin Xie; Guodong Liu; Xiaoli Dong; Jun Zhang; Xiaoyang Wang; Qinjun Peng; Zhimin Wang; Shenjin Zhang; Feng Yang; Chuangtian Chen; Zuyan Xu; Xi Dai; Zhong Fang; X. J. Zhou
The physical property investigation (like transport measurements) and ultimate application of the topological insulators usually involve surfaces that are exposed to ambient environment (1 atm and room temperature). One critical issue is how the topological surface state will behave under such ambient conditions. We report high resolution angle-resolved photoemission measurements to directly probe the surface state of the prototypical topological insulators, Bi2Se3 and Bi2Te3, upon exposing to various environments. We find that the topological order is robust even when the surface is exposed to air at room temperature. However, the surface state is strongly modified after such an exposure. Particularly, we have observed the formation of two-dimensional quantum well states near the exposed surface of the topological insulators. These findings provide key information in understanding the surface properties of the topological insulators under ambient environment and in engineering the topological surface state for applications.
Scientific Reports | 2015
Hemian Yi; Zhijun Wang; Chaoyu Chen; Youguo Shi; Ya Feng; Aiji Liang; Zhuojin Xie; Shaolong He; Junfeng He; Yingying Peng; Xu Liu; Yan Liu; Lin Zhao; Guodong Liu; Xiaoli Dong; Jun Zhang; Masashi Nakatake; M. Arita; Kenya Shimada; H. Namatame; M. Taniguchi; Zuyan Xu; Chuangtian Chen; Xi Dai; Zhong Fang; X. J. Zhou
The three-dimensional topological semimetals represent a new quantum state of matter. Distinct from the surface state in the topological insulators that exhibits linear dispersion in two-dimensional momentum plane, the three-dimensional semimetals host bulk band dispersions linearly along all directions. In addition to the gapless points in the bulk, the three-dimensional Weyl/Dirac semimetals are also characterized by “topologically protected” surface state with Fermi arcs on their surface. While Cd3As2 is proposed to be a viable candidate of a Dirac semimetal, more investigations are necessary to pin down its nature. In particular, the topological surface state, the hallmark of the three-dimensional semimetal, has not been observed in Cd3As2. Here we report the electronic structure of Cd3As2 investigated by angle-resolved photoemission measurements on the (112) crystal surface and detailed band structure calculations. The measured Fermi surface and band structure show a good agreement with the band structure calculations with two bulk Dirac-like bands approaching the Fermi level and forming Dirac points near the Brillouin zone center. Moreover, the topological surface state with a linear dispersion approaching the Fermi level is identified for the first time. These results provide experimental indications on the nature of topologically non-trivial three-dimensional Dirac cones in Cd3As2.
Scientific Reports | 2013
Chaoyu Chen; Zhuojin Xie; Ya Feng; Hemian Yi; Aiji Liang; Shaolong He; Daixiang Mou; Junfeng He; Yingying Peng; Xu Liu; Yan Liu; Lin Zhao; Guodong Liu; Xiaoli Dong; Jun Zhang; Li Yu; Xiaoyang Wang; Qinjun Peng; Zhimin Wang; Shenjin Zhang; Feng Yang; Chuangtian Chen; Zuyan Xu; X. J. Zhou
Three-dimensional topological insulators are characterized by insulating bulk state and metallic surface state involving relativistic Dirac fermions which are responsible for exotic quantum phenomena and potential applications in spintronics and quantum computations. It is essential to understand how the Dirac fermions interact with other electrons, phonons and disorders. Here we report super-high resolution angle-resolved photoemission studies on the Dirac fermion dynamics in the prototypical Bi2(Te,Se)3 topological insulators. We have directly revealed signatures of the electron-phonon coupling and found that the electron-disorder interaction dominates the scattering process. The Dirac fermion dynamics in Bi2(Te3−xSex) topological insulators can be tuned by varying the composition, x, or by controlling the charge carriers. Our findings provide crucial information in understanding and engineering the electron dynamics of the Dirac fermions for fundamental studies and potential applications.
Nature Communications | 2014
Zhuojin Xie; Shaolong He; Chaoyu Chen; Ya Feng; Hemian Yi; Aiji Liang; Lin Zhao; Daixiang Mou; Junfeng He; Yingying Peng; Xu Liu; Yan Liu; Guodong Liu; Xiaoli Dong; Li Yu; Jun Zhang; Shenjin Zhang; Zhimin Wang; Feng-Feng Zhang; Feng Yang; Qinjun Peng; Xiaoyang Wang; Chuangtian Chen; Zuyan Xu; X. J. Zhou
Topological insulators represent a new quantum state of matter that are insulating in the bulk but metallic on the edge or surface. In the Dirac surface state, it is well-established that the electron spin is locked with the crystal momentum. Here we report a new phenomenon of the spin texture locking with the orbital texture in a topological insulator Bi₂Se₃. We observe light-polarization-dependent spin texture of both the upper and lower Dirac cones that constitutes strong evidence of the orbital-dependent spin texture in Bi₂Se₃. The different spin texture detected in variable polarization geometry is the manifestation of the spin-orbital texture in the initial state combined with the photoemission matrix element effects. Our observations provide a new orbital degree of freedom and a new way of light manipulation in controlling the spin structure of the topological insulators that are important for their future applications in spin-related technologies.
Physical Review B | 2016
Baojie Feng; Yang-Hao Chan; Ya Feng; Ro-Ya Liu; M. Y. Chou; Kenta Kuroda; Koichiro Yaji; Ayumi Harasawa; Paolo Moras; Alexei Barinov; W. Malaeb; Cedric Bareille; Takeshi Kondo; Shik Shin; Fumio Komori; T.-C. Chiang; Youguo Shi; Iwao Matsuda
We determine the band structure and spin texture of
Nature Communications | 2017
Baojie Feng; Botao Fu; Shusuke Kasamatsu; Suguru Ito; Peng Cheng; Cheng-Cheng Liu; Ya Feng; S. F. Wu; Sanjoy K. Mahatha; P. M. Sheverdyaeva; Paolo Moras; M. Arita; Osamu Sugino; T.-C. Chiang; Kenya Shimada; Koji Miyamoto; Taichi Okuda; Kehui Wu; Lan Chen; Yugui Yao; Iwao Matsuda
{\mathrm{WTe}}_{2}
Proceedings of the National Academy of Sciences of the United States of America | 2016
Ya Feng; Defa Liu; Baojie Feng; Xu Liu; Lin Zhao; Zhuojin Xie; Yan Liu; Aiji Liang; Cheng Hu; Yong Hu; Shaolong He; Guodong Liu; Jun Zhang; Chuangtian Chen; Zuyan Xu; Lan Chen; Kehui Wu; Yu-Tzu Liu; Hsin Lin; Zhi-Quan Huang; Chia-Hsiu Hsu; Feng-Chuan Chuang; A. Bansil; X. J. Zhou
by spin- and angle-resolved photoemission spectroscopy (SARPES). With the support of first-principles calculations, we reveal the existence of spin polarization of both the Fermi arc surface states and bulk Fermi pockets. Our results support
Scientific Reports | 2015
Ya Feng; Zhijun Wang; Chaoyu Chen; Youguo Shi; Zhuojin Xie; Hemian Yi; Aiji Liang; Shaolong He; Junfeng He; Yingying Peng; Xu Liu; Yan Liu; Lin Zhao; Guodong Liu; Xiaoli Dong; Jun Zhang; Chuangtian Chen; Zuyan Xu; Xi Dai; Zhong Fang; X. J. Zhou
{\mathrm{WTe}}_{2}
Scientific Reports | 2015
Yan Liu; Li Yu; Xiaowen Jia; Jianzhou Zhao; Hongming Weng; Yingying Peng; Chaoyu Chen; Zhuojin Xie; Daixiang Mou; Junfeng He; Xu Liu; Ya Feng; Hemian Yi; Lin Zhao; Guodong Liu; Shaolong He; Xiaoli Dong; Jun Zhang; Zuyan Xu; Chuangtian Chen; G. Cao; Xi Dai; Zhong Fang; Xingjiang Zhou
to be a type-II Weyl semimetal candidate and provide important information to understand its extremely large and nonsaturating magnetoresistance.
Chinese Physics B | 2016
Aiji Liang; Chaoyu Chen; Zhijun Wang; Youguo Shi; Ya Feng; Hemian Yi; Zhuojin Xie; Shaolong He; Junfeng He; Yingying Peng; Yan Liu; Defa Liu; Cheng Hu; Lin Zhao; Guodong Liu; Xiaoli Dong; Jun Zhang; Masashi Nakatake; Hideaki Iwasawa; Kenya Shimada; M. Arita; H. Namatame; M. Taniguchi; Zuyan Xu; Chuangtian Chen; Hongming Weng; Xi Dai; Zhong Fang; Xingjiang Zhou
Topological nodal line semimetals, a novel quantum state of materials, possess topologically nontrivial valence and conduction bands that touch at a line near the Fermi level. The exotic band structure can lead to various novel properties, such as long-range Coulomb interaction and flat Landau levels. Recently, topological nodal lines have been observed in several bulk materials, such as PtSn4, ZrSiS, TlTaSe2 and PbTaSe2. However, in two-dimensional materials, experimental research on nodal line fermions is still lacking. Here, we report the discovery of two-dimensional Dirac nodal line fermions in monolayer Cu2Si based on combined theoretical calculations and angle-resolved photoemission spectroscopy measurements. The Dirac nodal lines in Cu2Si form two concentric loops centred around the Γ point and are protected by mirror reflection symmetry. Our results establish Cu2Si as a platform to study the novel physical properties in two-dimensional Dirac materials and provide opportunities to realize high-speed low-dissipation devices.Nodal line semimetals have been observed in three-dimensional materials but are missing in two-dimensional counterparts. Here, Feng et al. report two-dimensional Dirac nodal line fermions protected by mirror reflection symmetry in monolayer Cu2Si.