31 results on '"Cheng Maw Cheng"'
Search Results
2. Three-dimensional ultrafast charge-density-wave dynamics in CuTe
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Nguyen Nhat Quyen, Wen-Yen Tzeng, Chih-En Hsu, I-An Lin, Wan-Hsin Chen, Hao-Hsiang Jia, Sheng-Chiao Wang, Cheng-En Liu, Yu-Sheng Chen, Wei-Liang Chen, Ta-Lei Chou, I-Ta Wang, Chia-Nung Kuo, Chun-Liang Lin, Chien-Te Wu, Ping-Hui Lin, Shih-Chang Weng, Cheng-Maw Cheng, Chang-Yang Kuo, Chien-Ming Tu, Ming-Wen Chu, Yu-Ming Chang, Chin Shan Lue, Hung-Chung Hsueh, and Chih-Wei Luo
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Science - Abstract
Abstract Charge density waves (CDWs) involved with electronic and phononic subsystems simultaneously are a common quantum state in solid-state physics, especially in low-dimensional materials. However, CDW phase dynamics in various dimensions are yet to be studied, and their phase transition mechanism is currently moot. Here we show that using the distinct temperature evolution of orientation-dependent ultrafast electron and phonon dynamics, different dimensional CDW phases are verified in CuTe. When the temperature decreases, the shrinking of c-axis length accompanied with the appearance of interchain and interlayer interactions causes the quantum fluctuations (QF) of the CDW phase until 220 K. At T
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- 2024
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3. Determination of optical nonlinearity with photothermal effect within a layered bismuth telluride
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Jia-Chi Lan, Te-Yuan Chung, Cheng-Maw Cheng, Jung-Chun-Andrew Huang, and Chao-Kuei Lee
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Photothermal nonlinearity ,Optical nonlinearity ,Photothermal effect ,Nonlinear refractive index ,Z-scan ,Mining engineering. Metallurgy ,TN1-997 - Abstract
In this work, the photothermal nonlinearity within a layered bismuth telluride (Bi2Te3) is studied in detail. The dynamics of the optical nonlinearity with increasing photothermal effect are investigated via pump-probe spectroscopy. The difference between the thermally-induced and photon-induced nonlinearities was clarified and the entire photothermal nonlinearity was therefore sketched. Furthermore, by removing the thermally-induced background signal, the n2 without accumulated heat can then be estimated. For example, the n2 value is 2.80 × 10−8 cm2/W at a peak intensity of 12.81 MW/cm2. The results are compared with those obtained from another measurement to validate the reliability of the estimation. The working range of the n2 value is also discussed. To provide further validation of the feasibility of the proposed method, the photothermal nonlinearity within monolayer graphene is provided and discussed. This work provides an alternative method to deal with optical nonlinearity measurements that are subject to the photothermal effect, paving the way toward further related research.
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- 2023
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4. Kondo interaction in FeTe and its potential role in the magnetic order
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Younsik Kim, Min-Seok Kim, Dongwook Kim, Minjae Kim, Minsoo Kim, Cheng-Maw Cheng, Joonyoung Choi, Saegyeol Jung, Donghui Lu, Jong Hyuk Kim, Soohyun Cho, Dongjoon Song, Dongjin Oh, Li Yu, Young Jai Choi, Hyeong-Do Kim, Jung Hoon Han, Younjung Jo, Ji Hoon Shim, Jungpil Seo, Soonsang Huh, and Changyoung Kim
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Science - Abstract
Abstract Finding d-electron heavy fermion states has been an important topic as the diversity in d-electron materials can lead to many exotic Kondo effect-related phenomena or new states of matter such as correlation-driven topological Kondo insulator. Yet, obtaining direct spectroscopic evidence for a d-electron heavy fermion system has been elusive to date. Here, we report the observation of Kondo lattice behavior in an antiferromagnetic metal, FeTe, via angle-resolved photoemission spectroscopy, scanning tunneling spectroscopy and transport property measurements. The Kondo lattice behavior is represented by the emergence of a sharp quasiparticle and Fano-type tunneling spectra at low temperatures. The transport property measurements confirm the low-temperature Fermi liquid behavior and reveal successive coherent-incoherent crossover upon increasing temperature. We interpret the Kondo lattice behavior as a result of hybridization between localized Fe 3dxy and itinerant Te 5pz orbitals. Our observations strongly suggest unusual cooperation between Kondo lattice behavior and long-range magnetic order.
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- 2023
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5. Author Correction: Kondo interaction in FeTe and its potential role in the magnetic order
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Younsik Kim, Min-Seok Kim, Dongwook Kim, Minjae Kim, Minsoo Kim, Cheng-Maw Cheng, Joonyoung Choi, Saegyeol Jung, Donghui Lu, Jong Hyuk Kim, Soohyun Cho, Dongjoon Song, Dongjin Oh, Li Yu, Young Jai Choi, Hyeong-Do Kim, Jung Hoon Han, Younjung Jo, Ji Hoon Shim, Jungpil Seo, Soonsang Huh, and Changyoung Kim
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Science - Published
- 2024
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6. Formation of surface states on Pb(111) by Au adsorption
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Wei-Chuan Chen, Chin-Hsuan Chen, Angus Huang, Kaweng Lei, David Mikolas, Ming-kwan Dai, Je-Ming Kuo, Dai-Shien Lin, Cheng-Maw Cheng, H.-T. Jeng, and S.-J. Tang
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Medicine ,Science - Abstract
Abstract Using low-energy electron diffraction and angle-resolved photoemission spectroscopy, we investigated the lattice and electronic structures of the Pb(111) surface upon the adsorption of Au atoms at the low temperature T = 40 K. Unlike earlier results showing the formation of PbAu-alloy layers at room temperature, we found that Au atoms form a ultra-thin superstructure, Au/Pb(111)-3 × 3, on top of the Pb(111) surface. Moreover, three surface-state bands, S1, S2, and S3, are induced within and immediately adjacent to the Pb bulk projected band gap centered at the surface zone boundary $${\overline{\text{M}}}_{Pb(111)}$$ M ¯ P b ( 111 ) at the energies of − 0.02, − 1.05, and − 2.56 eV, respectively. First-principles calculation based on Au/Pb(111)-3 × 3 confirms the measured surface-state bands among which the most interesting are the S1 and S3 surface states. They are derived from surface resonances in Pb(111). Moreover, S1, which disperses across Fermi level, exhibits a large anisotropic Rashba splitting with α of 1.0 and 3.54 eVÅ in the two symmetry directions centered at $${\overline{\text{M}}}_{Pb(111)}$$ M ¯ P b ( 111 ) . The corresponding Rashba splitting of S1 bands in Cu/Pb(111)-3 × 3 and Ag/Pb(111)-3 × 3 was calculated for comparison.
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- 2023
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7. Efficient Hydrogen Evolution Reaction in 2H-MoS2 Basal Planes Enhanced by Surface Electron Accumulation
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Vimal Krishnamoorthy, Hemanth Kumar Bangolla, Chi-Yang Chen, Yu-Ting Huang, Cheng-Maw Cheng, Rajesh Kumar Ulaganathan, Raman Sankar, Kuei-Yi Lee, He-Yun Du, Li-Chyong Chen, Kuei-Hsieh Chen, and Ruei-San Chen
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molybdenum disulfide ,surface electron accumulation ,hydrogen evolution reaction ,overpotential ,Tafel slope ,Chemical technology ,TP1-1185 ,Chemistry ,QD1-999 - Abstract
An innovative strategy has been developed to activate the basal planes in molybdenum disulfide (MoS2) to improve their electrocatalytic activity by controlling surface electron accumulation (SEA) through aging, annealing, and nitrogen-plasma treatments. The optimal hydrogen evolution reaction (HER) performance was obtained on the surface treated with nitrogen-plasma for 120 s. An overpotential of 0.20 V and a Tafel slope of 120 mV dec−1 were achieved for the optimized condition. The angle-resolved photoemission spectroscopy measurement confirmed the HER efficiency enhanced by the SEA conjugated with the sulfur vacancy active sites in the MoS2 basal planes. This study provides new insight into optimizing MoS2 catalysts for energy applications.
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- 2024
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8. The Singularity Paramagnetic Peak of Bi0.3Sb1.7Te3 with p-type Surface State
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Shiu-Ming Huang, Pin-Cing Wang, Pin-Cyuan Chen, Jai-Long Hong, Cheng-Maw Cheng, Hao-Lun Jian, You-Jhih Yan, Shih-Hsun Yu, and Mitch M. C. Chou
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Paramagnetic susceptibility peak ,Topological material ,Dirac point ,Surface state ,Materials of engineering and construction. Mechanics of materials ,TA401-492 - Abstract
Abstract The magnetization measurement was performed in the Bi0.3Sb1.7Te3 single crystal. The magnetic susceptibility revealed a paramagnetic peak independent of the experimental temperature variation. It is speculated to be originated from the free-aligned spin texture at the Dirac point. The ARPES reveals that the Fermi level lies below the Dirac point. The Fermi wavevector extracted from the de Haas–van Alphen oscillation is consistent with the energy dispersion in the ARPES. Our experimental results support that the observed paramagnetic peak in the susceptibility curve does not originate from the free-aligned spin texture at the Dirac point.
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- 2022
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9. Author Correction: Formation of surface states on Pb(111) by Au adsorption
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Wei‑Chuan Chen, Chin‑Hsuan Chen, Angus Huang, Kaweng Lei, David Mikolas, Ming‑kwan Dai, Je‑Ming Kuo, Dai‑Shien Lin, Cheng‑Maw Cheng, H.‑T. Jeng, and S.‑J. Tang
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Medicine ,Science - Published
- 2023
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10. Robust charge-density wave strengthened by electron correlations in monolayer 1T-TaSe2 and 1T-NbSe2
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Yuki Nakata, Katsuaki Sugawara, Ashish Chainani, Hirofumi Oka, Changhua Bao, Shaohua Zhou, Pei-Yu Chuang, Cheng-Maw Cheng, Tappei Kawakami, Yasuaki Saruta, Tomoteru Fukumura, Shuyun Zhou, Takashi Takahashi, and Takafumi Sato
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Science - Abstract
Monolayer transition metal dechalcogenides are a promising platform to study the interplay of low-dimensionality and electron correlations. Here, the authors report a Mott insulator state in monolayer 1T-TaSe2, that survives far above room temperature and is robust against external perturbations.
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- 2021
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11. Direct observation of kink evolution due to Hund’s coupling on approach to metal-insulator transition in NiS2−x Se x
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Bo Gyu Jang, Garam Han, Ina Park, Dongwook Kim, Yoon Young Koh, Yeongkwan Kim, Wonshik Kyung, Hyeong-Do Kim, Cheng-Maw Cheng, Ku-Ding Tsuei, Kyung Dong Lee, Namjung Hur, Ji Hoon Shim, Changyoung Kim, and Gabriel Kotliar
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Science - Abstract
A decisive spectroscopic evidence of the Hund’s coupling energy scale in multi-orbital correlated systems has been lacking. Here, the authors identify a kink feature due to Hund´s coupling in the spectral function of NiS2x Se x as they track its evolution across the Mott-insulator transition.
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- 2021
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12. Epitaxial Growth and Structural Characterizations of MnBi2Te4 Thin Films in Nanoscale
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Shu-Hsuan Su, Jen-Te Chang, Pei-Yu Chuang, Ming-Chieh Tsai, Yu-Wei Peng, Min Kai Lee, Cheng-Maw Cheng, and Jung-Chung Andrew Huang
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MnBi2Te4 ,topological insulators ,antiferromagnetic order ,molecular beam epitaxy ,Chemistry ,QD1-999 - Abstract
The intrinsic magnetic topological insulator MnBi2Te4 has attracted much attention due to its special magnetic and topological properties. To date, most reports have focused on bulk or flake samples. For material integration and device applications, the epitaxial growth of MnBi2Te4 film in nanoscale is more important but challenging. Here, we report the growth of self-regulated MnBi2Te4 films by the molecular beam epitaxy. By tuning the substrate temperature to the optimal temperature for the growth surface, the stoichiometry of MnBi2Te4 becomes sensitive to the Mn/Bi flux ratio. Excessive and deficient Mn resulted in the formation of a MnTe and Bi2Te3 phase, respectively. The magnetic measurement of the 7 SL MnBi2Te4 film probed by the superconducting quantum interference device (SQUID) shows that the antiferromagnetic order occurring at the Néel temperature 22 K is accompanied by an anomalous magnetic hysteresis loop along the c-axis. The band structure measured by angle-resolved photoemission spectroscopy (ARPES) at 80 K reveals a Dirac-like surface state, which indicates that MnBi2Te4 has topological insulator properties in the paramagnetic phase. Our work demonstrates the key growth parameters for the design and optimization of the synthesis of nanoscale MnBi2Te4 films, which are of great significance for fundamental research and device applications involving antiferromagnetic topological insulators.
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- 2021
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13. Germanene structure enhancement by adjacent insoluble domains of lead
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Ting-Yu Chen, David Mikolas, Santosh Chiniwar, Angus Huang, Chung-Huang Lin, Cheng-Maw Cheng, Chung-Yu Mou, H.-T. Jeng, Woei Wu Pai, and S.-J. Tang
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Physics ,QC1-999 - Abstract
Growth of Xene, referred to as the analog of graphene made of atoms other than carbon, with higher lattice quality and more intrinsic electronic structures, is an important challenge to the development of two-dimensional (2D) materials. We report an approach using Pb-atom deposition to striped-phase (SP) germanene grown on Ag(111) to trigger it to a quasifreestanding phase (QP). Using low-energy electron diffraction (LEED) and scanning tunneling microscopy (STM), we demonstrate that the 2D monatomic Pb layer, instead of being on top, grows side-by-side with QP germanene, not only driving the SP-to-QP transition but further enhancing the lattice order of QP as revealed by the dramatic evolution of LEED-spot shape and uniform STM-imaged array of moiré patterns. Originally oriented at 30° to Ag(111), the QP germanene transits first to a narrow distribution of rotations then to two sharp domains at ±3° from 30°, while the monoatomic Pb domains twist from ±4.3° to ±9.5° with respect to Ag(111). The analysis of higher-order coincidence for both layers on Ag(111) is in complete agreement with LEED results and reveals a picture of two insoluble monatomic layers driving each other to a more optimal configuration. Moreover, the corresponding density of states measured by scanning tunneling spectroscopy for quality-enhanced QP germanene exhibits a clear V-shape distribution at the energy ∼0.4 eV above Fermi level, indicating the Fermi-Dirac cone, which agrees with our density functional theory calculation.
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- 2021
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14. Enhanced Ferromagnetic Interaction in Modulation-Doped GaMnN Nanorods
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Yuan-Ting Lin, Paritosh Vilas Wadekar, Hsiang-Shun Kao, Yu-Jung Zheng, Quark Yung-Sung Chen, Hui-Chun Huang, Cheng-Maw Cheng, New-Jin Ho, and Li-Wei Tu
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A1. Characterization ,A1. Doping ,A3. Molecular beam epitaxy ,B1. Nanomaterials ,B1. Nitrides ,B2. Magnetic materials ,Materials of engineering and construction. Mechanics of materials ,TA401-492 - Abstract
Abstract In this report, ferromagnetic interactions in modulation-doped GaMnN nanorods grown on Si (111) substrate by plasma-assisted molecular beam epitaxy are investigated with the prospect of achieving a room temperature ferromagnetic semiconductor. Our results indicate the thickness of GaN layer in each GaN/MnN pair, as well as Mn-doping levels, are essential for suppressing secondary phases as well as enhancing the magnetic moment. For these optimized samples, structural analysis by high-resolution X-ray diffractometry and Raman spectroscopy verifies single-crystalline modulation-doped GaMnN nanorods with Ga sites substituted by Mn atoms. Energy dispersive X-ray spectrometry shows that the average Mn concentration can be raised from 0.4 to 1.8% by increasing Mn fluxes without formation of secondary phases resulted in a notable enhancement of the saturation magnetization as well as coercive force in these nanorods.
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- 2017
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15. Robust charge-density wave strengthened by electron correlations in monolayer 1T-TaSe2 and 1T-NbSe2
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Cheng Maw Cheng, Takashi Takahashi, Shuyun Zhou, Changhua Bao, Tomoteru Fukumura, Ashish Chainani, Katsuaki Sugawara, Hirofumi Oka, Takafumi Sato, Pei Yu Chuang, Shaohua Zhou, Yuki Nakata, Yasuaki Saruta, and Tappei Kawakami
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Materials science ,Science ,General Physics and Astronomy ,FOS: Physical sciences ,Electron ,General Biochemistry, Genetics and Molecular Biology ,Condensed Matter - Strongly Correlated Electrons ,Condensed Matter::Materials Science ,Phase (matter) ,Condensed Matter::Superconductivity ,Monolayer ,Superconductivity ,Condensed Matter::Quantum Gases ,Condensed Matter - Materials Science ,Multidisciplinary ,Condensed matter physics ,Electronic correlation ,Strongly Correlated Electrons (cond-mat.str-el) ,Condensed Matter::Other ,Transition temperature ,Materials Science (cond-mat.mtrl-sci) ,General Chemistry ,Photoexcitation ,Condensed Matter::Strongly Correlated Electrons ,Charge density wave - Abstract
Combination of low-dimensionality and electron correlation is vital for exotic quantum phenomena such as the Mott-insulating phase and high-temperature superconductivity. Transition-metal dichalcogenide (TMD) 1T-TaS2 has evoked great interest owing to its unique nonmagnetic Mott-insulator nature coupled with a charge-density-wave (CDW). To functionalize such a complex phase, it is essential to enhance the CDW-Mott transition temperature TCDW-Mott, whereas this was difficult for bulk TMDs with TCDW-Mott 2. Furthermore, the electron correlation derived lower Hubbard band survives under external perturbations such as carrier doping and photoexcitation, in contrast to the bulk counterpart. The enhanced Mott-Hubbard and CDW gaps for monolayer TaSe2 compared to NbSe2, originating in the lattice distortion assisted by strengthened correlations and disappearance of interlayer hopping, suggest stabilization of a likely nonmagnetic CDW-Mott insulator phase well above the room temperature. The present result lays the foundation for realizing monolayer CDW-Mott insulator based devices operating at room temperature.
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- 2021
16. Direct observation of kink evolution due to Hund’s coupling on approach to metal-insulator transition in NiS2−x Se x
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Gabriel Kotliar, Ji Hoon Shim, Yoon Young Koh, Hyeong-Do Kim, Cheng Maw Cheng, Wonshik Kyung, Garam Han, Ina Park, Namjung Hur, Ku Ding Tsuei, Dong-Wook Kim, Changyoung Kim, Yeongkwan Kim, Bo Gyu Jang, and Kyung Dong Lee
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Physics ,Multidisciplinary ,Condensed matter physics ,Science ,General Physics and Astronomy ,Angle-resolved photoemission spectroscopy ,02 engineering and technology ,General Chemistry ,Electron ,021001 nanoscience & nanotechnology ,01 natural sciences ,General Biochemistry, Genetics and Molecular Biology ,Coupling (physics) ,0103 physical sciences ,Coulomb ,Density functional theory ,Condensed Matter::Strongly Correlated Electrons ,Fermi liquid theory ,Metal–insulator transition ,010306 general physics ,0210 nano-technology ,Characteristic energy - Abstract
Understanding characteristic energy scales is a fundamentally important issue in the study of strongly correlated systems. In multiband systems, an energy scale is affected not only by the effective Coulomb interaction but also by the Hund’s coupling. Direct observation of such energy scale has been elusive so far in spite of extensive studies. Here, we report the observation of a kink structure in the low energy dispersion of NiS2−xSex and its characteristic evolution with x, by using angle resolved photoemission spectroscopy. Dynamical mean field theory calculation combined with density functional theory confirms that this kink originates from Hund’s coupling. We find that the abrupt deviation from the Fermi liquid behavior in the electron self-energy results in the kink feature at low energy scale and that the kink is directly related to the coherence-incoherence crossover temperature scale. Our results mark the direct observation of the evolution of the characteristic temperature scale via kink features in the spectral function, which is the hallmark of Hund’s physics in the multiorbital system.
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- 2021
17. Corrigendum: Significantly enhanced giant Rashba splitting in a thin film of binary alloy (2015 New J. Phys. 17 083015)
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Wei-Chuan Chen, Tay-Rong Chang, Sun-Ting Tsai, Sh Yamamoto, Je-Ming Kuo, Cheng-Maw Cheng, Ku-Ding Tsuei, Koichiro Yaji, Hsin Lin, H-T Jeng, Chung-Yu Mou, Iwao Matsuda, and S-J Tang
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Science ,Physics ,QC1-999 - Published
- 2015
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18. Significantly enhanced giant Rashba splitting in a thin film of binary alloy
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Wei-Chuan Chen, Tay-Rong Chang, Sun-Ting Tsai, S Yamamoto, Je-Ming Kuo, Cheng-Maw Cheng, Ku-Ding Tsuei, Koichiro Yaji, Hsin Lin, H-T Jeng, Chung-Yu Mou, Iwao Matsuda, and S-J Tang
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giant Rashba splitting ,binary alloy ,Pb and Au ,Science ,Physics ,QC1-999 - Abstract
Dirac cones in a two-dimensional environment have attracted much attention not only because of the massless Dirac fermions but also due to their capability to lock the spin direction with the momentum. Here we demonstrate that the Rashba effect within a single layer of a binary alloy composed of heavy atoms, Pb and Au, can be driven by and even tweaked with the adjacent top and bottom layers to yield cone-like structures and further enhance the Rashba coupling strength. Two cones are observed at the surface zone center $\bar{\Gamma }$ with giant Rashba parameters 1.53 and 4.45 eVÅ; an anisotropic giant Rashba splitting at the surface zone boundary $\bar{M}$ has a great value, 6.26 eVÅ, inferring the critical role of p - d hybridization between Pb and Au. Our results reveal not only an interesting natural phenomenon but also a feasible method of tweaking the Rashba effect of a two-dimensional system.
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- 2015
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19. Probing the Origin of Extreme Magnetoresistance in Pr/Sm Mono-Antimonides/Bismuthides
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Tai-Chang Chiang, Fan Wu, Cheng-Maw Cheng, Zhe Sun, Huiqiu Yuan, Peng Li, Yang Liu, Chao Cao, Zhongzheng Wu, Chunyu Guo, and Yi Liu
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Electron mobility ,Condensed Matter - Materials Science ,Materials science ,Magnetoresistance ,Condensed matter physics ,Condensed Matter - Mesoscale and Nanoscale Physics ,Photoemission spectroscopy ,Quantum oscillations ,Materials Science (cond-mat.mtrl-sci) ,FOS: Physical sciences ,02 engineering and technology ,Condensed Matter::Mesoscopic Systems and Quantum Hall Effect ,021001 nanoscience & nanotechnology ,01 natural sciences ,Transition point ,Hall effect ,0103 physical sciences ,Mesoscale and Nanoscale Physics (cond-mat.mes-hall) ,Condensed Matter::Strongly Correlated Electrons ,010306 general physics ,0210 nano-technology ,Electronic band structure ,Surface states - Abstract
Combining angle-resolved photoemission spectroscopy and magneto-transport measurements, we systematically investigated the possible origin of the extreme magnetoresistance in Pr/Sm mono-antimonides/bismuthides (PrSb, SmSb, PrBi, SmBi). Our photoemission measurements reveal that the bulk band inversion and surface states are absent (present) in Pr/Sm antimonides (bismuthides), implying that topological surface states are unlikely to play an important role for the observed extreme magnetoresistance. We found that the electron-hole compensation is well satisfied in all these compounds and the bulk band structure exhibits no obvious temperature dependence from 10 K up to 150 K. Simultaneous fittings of the magnetoresistance and Hall coefficient reveal that the carrier mobility is dramatically enhanced at low temperature, which naturally explains the suppression of extreme magnetoresistance at high temperatures. Our results therefore show that the extreme magnetoresistance in these compounds can be well accounted for by the two-band model with good electron-hole compensation. Finally, we found that both PrSb and SmSb exhibit highly linear bulk bands near the X point and lie close to the transition point between a topologically trivial and nontrivial phase, which might be relevant for the observed anomalous quantum oscillations., 6 figures
- Published
- 2019
20. Rashba effect within the space–charge layer of a semiconductor
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Chung-Huang Lin, Tay-Rong Chang, Ro-Ya Liu, Cheng-Maw Cheng, Ku-Ding Tsuei, H -T Jeng, Chung-Yu Mou, Iwao Matsuda, and S -J Tang
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semiconductor band edges ,space–charge layer ,Rashba effect ,Science ,Physics ,QC1-999 - Abstract
The observed heavy-hole, light-hole and split-off band edges of a semiconductor are the well known consequence of two physical processes: atomic spin–orbital interaction and solid-state band–band anticrossing. In this work, we examined the four band-edge-like bands in great detail within the Ge space–charge layer with either Pb/Ge(111)- $\sqrt{3}\times \sqrt{3}$ R30° or a 2 ML Pb film on Ge(111). Our results reveal that the conventional picture of band edges for a semiconductor is actually crude. In addition, momentum-dependent Rashba splitting effect can be included to explain the observed non-split-off band, indicating the Rashba effect as an intrinsic property near a semiconductor surface.
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- 2014
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21. Efficient n-type Doping in Epitaxial Graphene through Strong Lateral Orbital Hybridization of Ti Adsorbate
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Camilla Coletti, Cheng Maw Cheng, Hao Chun Huang, Chia Hao Chen, Stefan Heun, Chung Lin Wu, Forest Shih-Sen Chien, Lo-Yueh Chang, Domenica Convertino, Ming-Fa Lin, Jhih Wei Chen, Yi-Chun Chen, and Hung-Wei Shiu
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Materials science ,Photoemission spectroscopy ,Orbital hybridisation ,FOS: Physical sciences ,Angle-resolved photoemission spectroscopy ,02 engineering and technology ,01 natural sciences ,law.invention ,Condensed Matter::Materials Science ,Atomic orbital ,law ,Condensed Matter::Superconductivity ,Mesoscale and Nanoscale Physics (cond-mat.mes-hall) ,0103 physical sciences ,Atom ,Physics::Atomic and Molecular Clusters ,General Materials Science ,Physics::Chemical Physics ,010306 general physics ,Condensed Matter - Materials Science ,Condensed matter physics ,Condensed Matter - Mesoscale and Nanoscale Physics ,Graphene ,Doping ,Materials Science (cond-mat.mtrl-sci) ,General Chemistry ,021001 nanoscience & nanotechnology ,3. Good health ,Condensed Matter::Strongly Correlated Electrons ,0210 nano-technology ,Graphene nanoribbons - Abstract
In recent years, various doping methods for epitaxial graphene have been demonstrated through atom substitution and adsorption. Here we observe by angle-resolved photoemission spectroscopy (ARPES) a coupling-induced Dirac cone renormalization when depositing small amounts of Ti onto epitaxial graphene on SiC. We obtain a remarkably high doping efficiency and a readily tunable carrier velocity simply by changing the amount of deposited Ti. First-principles theoretical calculations show that a strong lateral (non-vertical) orbital coupling leads to an efficient doping of graphene by hybridizing the 2pz orbital of graphene and the 3d orbitals of the Ti adsorbate, which attached on graphene without creating any trap/scattering states. This Ti-induced hybridization is adsorbate-specific and has major consequences for efficient doping as well as applications towards adsorbate-induced modification of carrier transport in graphene., 24 pages, 4 figures
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- 2016
22. Selective Hydrogen Etching Leads to 2D Bi(111) Bilayers on Bi2Se3: Large Rashba Splitting in Topological Insulator Heterostructure.
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Shu Hsuan Su, Pei Yu Chuang, Sheng Wen Chen, Hsin Yu Chen, Yi Tung, Wei-Chuan Chen, Chia-Hsin Wang, Yaw-Wen Yang, Jung Chun Andrew, Huang, Tay-Rong Chang, Hsin Lin, Horng-Tay Jeng, Cheng-Maw Cheng, Ku-Ding Tsuei, Hai Lin Su, and Yu Cheng Wu
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- 2017
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23. The Density of States and the Transport Effective Mass in a Highly Oriented Semiconducting Polymer: Electronic Delocalization in 1D.
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Ben Bang-Yu Hsu, Cheng-Maw Cheng, Chan Luo, Patel, Shrayesh N., Cheng Zhong, Haitao Sun, Sherman, Jessica, Byoung Hoon Lee, Lei Ying, Ming Wang, Bazan, Guillermo, Chabinyc, Michael, Brédas, Jean-Luc, and Heeger, Alan
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- 2015
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24. Bilayer oscillation of subband effective masses in Pb/Ge(111) thin-film quantum wells.
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Tang, S.-J., Chang-Yeh Lee, Chien-Chung Huang, Tay-Rong Chang, Cheng-Maw Cheng, Ku-Ding Tsuei, and Jeng, H.-T.
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THIN films ,QUANTUM wells ,FREE electron theory of metals ,MONOMOLECULAR films ,ELECTRON emission - Abstract
Subband dispersions of quantum-well states in Pb thin films on Ge(111) have been measured with angle-resolved photoemission spectroscopy. The effective masses at the surface zone center exhibit a bilayer oscillation with thickness, in both magnitude and sign. This behavior is attributed to a strong interaction between Pb quantum-well subbands and the Ge valence maximum near the Fermi level, which occurs about every two monolayers. [ABSTRACT FROM AUTHOR]
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- 2010
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25. Shubnikov–de Haas oscillation of Bi2Te3 topological insulators with cm-scale uniformity.
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Shiu-Ming Huang, Shao-Yu Lin, Jui-Fang Chen, Chao-Kuei Lee, Shih-Hsun Yu, Mitch M C Chou, Cheng-Maw Cheng, and Hung-Duen Yang
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SHUBNIKOV-de Haas effect ,TOPOLOGICAL insulators ,PHOTOELECTRON spectroscopy ,BISMUTH telluride ,OSCILLATIONS - Abstract
A topological insulating Bi
2 Te3 single crystal was successfully grown with good uniformity using a home-made resistance-heated floated zone furnace. The temperature-dependent resistance and Hall voltage confirm that the transport is metallic and the overall carriersareholes. The angle and temperature dependence of the quantum Shubnikov–de Haas oscillation period amplitude suggests that the transport comes from the carriers of surface states. The Berry phase, determined from Landau level diagram, also reveals that the transport carriers are Dirac fermions. In contrast with many previous publications, the transport parameters relating to the surface carriers derived from the relationship of the Lifshitz–Kosevich (LK) theory are consistent with angle resolved photoemission spectroscopy results. [ABSTRACT FROM AUTHOR]- Published
- 2016
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26. Corrigendum: Significantly enhanced giant Rashba splitting in a thin film of binary alloy (2015 New J. Phys.17 083015).
- Author
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Wei-Chuan Chen, Tay-Rong Chang, Sun-Ting Tsai, Sh Yamamoto, Je-Ming Kuo, Cheng-Maw Cheng, Ku-Ding Tsuei, Koichiro Yaji, Hsin Lin, H-T Jeng, Chung-Yu Mou, Iwao Matsuda, and S-J Tang
- Subjects
RASHBA effect ,ENERGY bands - Abstract
A correction to an article on enhanced giant Rashba splitting is presented.
- Published
- 2015
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27. Deeper insight into phase relations in ultrathin Pb films.
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Ro-Ya Liu, Angus Huang, Chien-Chung Huang, Chang-Yeh Lee, Chung-Huang Lin, Cheng-Maw Cheng, Ku-Ding Tsuei, Horng-Tay Jeng, Iwao Matsuda, and Tang, S.-J.
- Subjects
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MONOMOLECULAR films , *LEAD , *QUANTUM wells , *PHOTOELECTRON spectroscopy , *ELECTRON work function - Abstract
Films of Pb(111) with thickness ranging from 1 to 16 monolayers (ML) were grown on Ge(111) and examined by angle-resolved photoemission spectroscopy. The measured thickness dependences of the work function and surface energy from the same set of samples were both well described by damped sinusoidal oscillatory functions with the same period, but the oscillation phases differ by 1/4 period between the two quantities, as judged by the node positions. This difference agrees with the prediction of a generic quantum-well model. The varied node positions of damped oscillations of the work function and surface energy were examined in terms of the details of Pb subband dispersions, indicating the different roles of the density of states at the Fermi level to both thin-film properties. The surface dipoles of Pb films were found to have no relevant effects on the phase shift of thickness-dependent work functions except for the amplitudes of oscillations. The total boundary phase shifts of the quantum well states, extracted from the energy positions of the quantum-well states for both Pb/Ge(111) and freestanding Pb films, are compared and related to the thickness-dependent work function and surface energy. [ABSTRACT FROM AUTHOR]
- Published
- 2015
- Full Text
- View/download PDF
28. Consonant diminution of lattice and electronic coupling between a film and a substrate: Pb on Ge(100).
- Author
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Pei-Wen Chen, Yu-Hsuan Lu, Tay-Rong Chang, Chi-Bin Wang, Li-Yen Liang, Chung-Huang Lin, Cheng-Maw Cheng, Ku-Ding Tsuei, Jeng, H.-T., and Tang, S.-J.
- Subjects
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ELECTRONIC structure , *GERMANIUM , *PHOTOELECTRON spectroscopy , *LOW energy electron diffraction , *ELECTRON diffraction , *LATTICE theory - Abstract
The dependence on thickness of electronic and lattice structures of Pb films deposited on Ge(100) substrate was investigated with angle-resolved photoemission spectroscopy and low-energy electron diffraction. Pb films grew in the (111) surface direction with two (1 x 1) domains rotated 90 º relative to each other despite a square lattice of Ge(100); correspondingly, the heavy-hole band edge of Ge does not interact with quantum-well-state bands of Pb films. Symmetry arguments in terms of orbitals of Pb quantum-well states and Ge band edges correlate the consonant diminution of lattice and electronic coupling between the film and the substrate. [ABSTRACT FROM AUTHOR]
- Published
- 2011
- Full Text
- View/download PDF
29. Electronic versus Lattice Match for Metal-Semiconductor Epitaxial Growth: Pb on Ge(111).
- Author
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Tang, S.-J., Chang-Yeh Lee, Chien-Chung Huang, Tay-Rong Chang, Cheng-Maw Cheng, Ku-Ding Tsuei, H.-T. Jeng, V. Yeh, and Tai-Chang Chiang
- Subjects
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SEMICONDUCTORS , *METALS , *EPITAXY , *THIN films , *OSCILLATIONS - Abstract
Lattice match is important for epitaxial growth. We show that a competing mechanism, electronic match, can dominate at small film thicknesses for metal-semiconductor systems, where quantum confinement and symmetry requirements may favor a different growth pattern. For Pb(111) on Ge(111), an accidental lattice match leads to 3 × 3on involving a 30° in-plane rotation at large film thicknesses, but it gives way to an incommensurate (1 × 1) configuration at small film thickness. The transformation follows an approximately inverse-film-thickness dependence with super- imposed bilayer oscillations. [ABSTRACT FROM AUTHOR]
- Published
- 2011
- Full Text
- View/download PDF
30. Mixed-state Hall effect and flux pinning in Ba(Fe1-xCox)2As2 single crystals (x=0.08 and 0.10).
- Author
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Wang, L. M., Un-Cheong Sou, Yang, H. C., Chang, L. J., Cheng-Maw Cheng, Ku-Ding Tsuei, Su, Y., Wolf, Th., and Adelmann, P.
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HALL effect , *FLUX pinning , *MAGNETIZATION , *CRYSTALS , *CRYSTALLOGRAPHY - Abstract
Longitudinal and Hall resistivities, scaling behavior, and magnetizations are examined to study the effect of flux pinning in Ba(Fe1-xCox)2As2 (BFCA) single crystals with x?=?0.08 and 0.01. Larger values of activation energy, critical current density, and pinning force are obtained in BFCA with x?=?0.10, indicating relatively strong pinning. The sign reversal of Hall resistivities is clearly observed in BFCA with x?=?0.10. The correlation between longitudinal and Hall resistivities shows the scaling behavior of ρxy∞(ρxx)β with exponents β?=?3.0-3.4 and 2.0?α?0.2 for BFCA crystals with x?=?0.08 and 0.10, respectively. Furthermore, the normal-state Hall angle is also observed to follow cot θH=ΛT2 + C in BFCA crystals, and is explained by the Anderson theory. The relatively large c/Λ value for BFCA with x?=?0.10 also implies a larger contribution of impurity scattering due to more Co atoms, which may cause stronger pinning of flux lines. The results are analyzed and coincide with theory, including the pinning-induced backflow effect and plastic flow mechanism in vortex dynamics. [ABSTRACT FROM AUTHOR]
- Published
- 2011
- Full Text
- View/download PDF
31. Helicity-dependent terahertz emission spectroscopy of topological insulator Sb2Te3 thin films.
- Author
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Chien-Ming Tu, Yi-Cheng Chen, Ping Huang, Pei-Yu Chuang, Ming-Yu Lin, Cheng-Maw Cheng, Jiunn-Yuan Lin, Jenh-Yih Juang, Kaung-Hsiung Wu, Huang, Jung-Chun A., Way-Faung Pong, Takayoshi Kobayashi, and Chih-Wei Luo
- Subjects
- *
TERAHERTZ spectroscopy , *TERAHERTZ materials , *HELICITY (Chemistry) , *EMISSION spectroscopy , *SPINTRONICS - Abstract
We report on helicity-dependent terahertz emissions that originate from the helicity-dependent photocurrents in topological insulator Sb2Te3 thin films due to ultrafast optical excitation. The polarity of the emitted terahertz radiation is controlled by both the incident angle and the helicity of optical pulses. Using an unprecedented decomposition-recombination procedure in the time domain, the signals of the Dirac fermions are fully separated from bulk contributions. These results provide insights into the optical coupling of topological surface states and open up opportunities for applying helicity-dependent terahertz emission spectroscopy in spintronics. [ABSTRACT FROM AUTHOR]
- Published
- 2017
- Full Text
- View/download PDF
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