Article
Chemistry, Multidisciplinary
Runzhe Xu, Yunhe Bai, Jingsong Zhou, Jiaheng Li, Xu Gu, Na Qin, Zhongxu Yin, Xian Du, Qinqin Zhang, Wenxuan Zhao, Yidian Li, Yang Wu, Cui Ding, Lili Wang, Aiji Liang, Zhongkai Liu, Yong Xu, Xiao Feng, Ke He, Yulin Chen, Lexian Yang
Summary: The electronic structure of MnBi2Te4 thin films evolves from an insulator type to in-gap topological surface states with increasing film thickness, and a Rashba split band gradually emerges and hybridizes with topological surface states through surface doping.
Article
Materials Science, Multidisciplinary
Jingwei Dong, Dongbin Shin, Ernest Pastor, Tobias Ritschel, Laurent Cario, Zhesheng Chen, Weiyan Qi, Romain Grasset, Marino Marsi, Amina Taleb-Ibrahimi, Noejung Park, Angel Rubio, Luca Perfetti, Evangelos Papalazarou
Summary: We used angle and time-resolved photoelectron spectroscopy to study the commensurate charge density wave (CDW) phase of 1T-TaS2. We employed different probe pulse polarizations to map the dispersion of electronic states above and below the chemical potential. Upon photoexcitation, the fluctuations of CDW order erased the band dispersion and squeezed the electronic states near the chemical potential. This transient phase developed within half a period of coherent lattice motion and was influenced by strong electronic correlations. Our simulations indicated that the screening of Coulomb repulsion depended on the stacking order of the TaS2 layers. The entanglement of these degrees of freedom suggested that both the structural order and electronic repulsion were locally modified by the photoinduced CDW fluctuations.
Article
Chemistry, Multidisciplinary
Deepnarayan Biswas, Alfred J. H. Jones, Paulina Majchrzak, Byoung Ki Choi, Tsung-Han Lee, Klara Volckaert, Jiagui Feng, Igor Markovic, Federico Andreatta, Chang-Jong Kang, Hyuk Jin Kim, In Hak Lee, Chris Jozwiak, Eli Rotenberg, Aaron Bostwick, Charlotte E. Sanders, Yu Zhang, Gabriel Karras, Richard T. Chapman, Adam S. Wyatt, Emma Springate, Jill A. Miwa, Philip Hofmann, Phil D. C. King, Young Jun Chang, Nicola Lanata, Soren Ulstrup
Summary: The study reveals that the interaction between electronic and lattice degrees of freedom in single-layer VSe2 leads to the charge density wave transition. In the insulating state, a light-induced closure of the energy gap was observed.
Article
Chemistry, Multidisciplinary
Paul Dreher, Wen Wan, Alla Chikina, Marco Bianchi, Haojie Guo, Rishav Harsh, Samuel Manas-Valero, Eugenio Coronado, Antonio J. Martinez-Galera, Philip Hofmann, Jill A. Miwa, Miguel M. Ugeda
Summary: The study reveals that the CDW and superconducting states in single-layer NbSe2 exhibit different behaviors on different substrates, with these electronic phases remaining stable on graphene and boron nitride substrates but severely weakened or even absent on metallic substrates.
Article
Chemistry, Multidisciplinary
E. Rongione, L. Baringthon, D. She, G. Patriarche, R. Lebrun, A. Lemaitre, M. Morassi, N. Reyren, M. Micica, J. Mangeney, J. Tignon, F. Bertran, S. Dhillon, P. Le Fevre, H. Jaffres, J. -m. George
Summary: By combining spin- and angle-resolved photoemission spectroscopy with time-resolved THz emission spectroscopy, it is demonstrated that spin-charge conversion mainly arises from the surface state in ultrathin films of Bi1-xSbx. The robustness of the surface state and the significant conversion efficiency in epitaxial Bi1-xSbx thin films bring new perspectives for ultra-low power magnetic random-access memories and broadband THz generation.
Article
Materials Science, Multidisciplinary
Sven Schemmelmann, Peter Krueger, Fabian Schoettke, Markus Donath
Summary: The unoccupied electronic structure of the Re (0001) surface was investigated using spin- and angle-resolved inverse photoemission, both experimentally and theoretically. The study focused on states around the center of the surface Brillouin zone F, where a hole pocket of a surface state with Rashba-type spin splitting was detected. Spin-dependent photon emission from unpolarized surface and bulk states at F was observed, with the spin asymmetry being dependent on experimental parameters such as electron spin polarization direction and photon detection angle. The observed effect is attributed to spin-orbit-induced hybridization of the involved states.
Article
Chemistry, Physical
Mukhtar Lawan Adam, Hongen Zhu, Zhanfeng Liu, Shengtao Cui, Pengjun Zhang, Yi Liu, Guobin Zhang, Xiaojun Wu, Zhe Sun, Li Song
Summary: By intercalating Sn atoms, the CDW phase in 1T-TiSe2 single crystals can be gradually suppressed, inducing charge doping and modulating the intrinsic electronic properties. Temperature-dependent ARPES results reveal the role of exciton-phonon interaction and the Jahn-Teller mechanism in the formation of CDW in this material.
Article
Physics, Applied
L. B. Lei, C. Zhang, A. B. Yu, Y. F. Wu, W. Peng, H. Xiao, S. Qiao, T. Hu
Summary: Competing orders in a two-dimensional limit play a crucial role in understanding unconventional superconductivity. By fabricating an ultrathin 2H-NbSe2 device and conducting transport measurements, superconducting and CDW transitions were observed, with the superconducting gap estimated using BTK theory. Features resembling a precursor superconductivity similar to cuprate superconductors were also identified in the normal state.
SUPERCONDUCTOR SCIENCE & TECHNOLOGY
(2021)
Article
Physics, Multidisciplinary
Zilu Wang, Haoyu Dong, Weichang Zhou, Zhihai Cheng, Shancai Wang
Summary: We report high-resolution angle-resolved photoemission spectroscopy (ARPES) studies on the electronic structure of Ti-doped 1T-Ti x Ta1-x S2 with different doping levels. A flat band originating from the formation of the star of David super-cell is observed in the x = 5% sample at low temperature. With increasing Ti doping levels, the flat band disappears in the x = 8% sample due to extra hole carriers. The localized flat band and correlation effect in 1T-TMDCs can be tuned by changing the filling factor through doping electron or hole carriers.
Article
Chemistry, Multidisciplinary
Yaoyao Chen, Yu Zhang, Wei Wang, Xuan Song, Liang-Guang Jia, Can Zhang, Lili Zhou, Xu Han, Hui-Xia Yang, Li-Wei Liu, Chen Si, Hong-Jun Gao, Ye-Liang Wang
Summary: Direct evidence of confined electronic states and charge density modulations at mirror twin boundaries (MTBs) of monolayer NbSe2 is provided through scanning tunneling microscopy measurements and first-principles calculations. The results reveal the behavior of confined electrons at MTBs and provide a theoretical basis for grain boundary engineering of functionality.
Article
Chemistry, Physical
Zhanfeng Liu, Tongrui Li, Wen Zhu, Hongwei Shou, Mukhtar Lawan Adam, Qilong Cui, Yuliang Li, Sheng Wang, Yunbo Wu, Hongen Zhu, Yi Liu, Shuangming Chen, Xiaojun Wu, Shengtao Cui, Li Song, Zhe Sun
Summary: Charge density wave (CDW) is a phenomenon that occurs in materials, accompanied by changes in their intrinsic electronic properties. The study of CDW and its modulation in materials holds tremendous significance in materials research, as it provides a unique approach to controlling the electronic properties of materials. Through V substitution for Ti in TiSe2, we tuned the carrier concentration in VxTi1-xSe2 to study how its electronic structures evolve. ARPES shows that the band-folding effect is sustained with the doping level up to 10%, indicating the persistence of the CDW phase, even though the band structure is strikingly different from that of the parent compound TiSe2. Our work provides a constraint for understanding the CDW mechanism in TiSe2, and highlights the role of lattice distortion in the band-folding effect.
Article
Chemistry, Multidisciplinary
Mohammed K. Bin Subhan, Asif Suleman, Gareth Moore, Peter Phu, Moritz Hoesch, Hidekazu Kurebayashi, Christopher A. Howard, Steven R. Schofield
Summary: This study reports the discovery of a CDW ground state in heavily electron-doped MoS2, demonstrating a metal-insulator transition, a 25 meV gap at the Fermi level, and two distinct CDW modulations attributed to Fermi surface nesting and electron-phonon coupling. The simultaneous exhibition of these CDW modulations provides new insight into the origin of CDWs in transition metal dichalcogenides.
Article
Chemistry, Physical
V. Polewczyk, S. K. Chaluvadi, D. Dagur, F. Mazzola, S. Punathum Chalil, A. Y. Petrov, J. Fujii, G. Panaccione, G. Rossi, P. Orgiani, G. Vinai, P. Torelli
Summary: V2O3 exhibits a complex relationship between the metal-insulator transition and the structural rhombohedral-monoclinic one, as well as its dependency on sample thickness. Investigation of thin and ultra-thin film growth is crucial in understanding the chemical, electronic, and structural phases, as well as the role of the substrate interface. Our study examines the thickness-dependent properties of V2O3 films grown on c-plane Al2O3 substrates, revealing the evolution of surface morphology and its implications on overall properties.
APPLIED SURFACE SCIENCE
(2023)
Article
Chemistry, Physical
I. Palacio, J. Obando-Guevara, L. Chen, M. N. Nair, M. A. Gonzalez Bario, E. Papalazarou, P. Le Fevre, A. Taleb-Ibrahimi, E. G. Michel, A. Mascaraque, A. Tejeda
Summary: The temperature-dependent electronic structure of the light rare-earth antimonide LaSb2 was studied using angle-resolved photoemission (ARPES) measurements and density functional theory (DFT) calculations. The results showed the appearance of band replicas and a folded band at low temperature, indicating the presence of a charge density wave in LaSb2.
APPLIED SURFACE SCIENCE
(2023)
Article
Physics, Multidisciplinary
Alexander Osterkorn, Constantin Meyer, Salvatore R. Manmana
Summary: This study reveals that in a driven strongly interacting system, a band-like resonance is formed in the gap region. This phenomenon is associated with the Villain mode and appears in both equilibrium and non-equilibrium states.
COMMUNICATIONS PHYSICS
(2023)
Article
Materials Science, Multidisciplinary
Takumi Fukuda, Ryota Kaburauchi, Yuta Saito, Kotaro Makino, Paul Fons, Keiji Ueno, Muneaki Hase
Summary: In this study, coherent phonon spectroscopy is used to investigate the relationship between structural phase transitions and photo-thermal effects in polymorphic MoTe2 single crystals. The results show that increasing excitation density leads to tellurium segregation, but no structural phase transition is observed among the polymorphs of MoTe2. However, higher photon-energy excitation is found to suppress tellurium segregation.
PHYSICA STATUS SOLIDI-RAPID RESEARCH LETTERS
(2022)
Article
Physics, Applied
Arifuzzaman Rajib, Abdul Kuddus, Kojun Yokoyama, Tomohiro Shida, Keiji Ueno, Hajime Shirai
Summary: In this study, the synthesis of amorphous aluminum titanium oxide thin films and their application as high dielectric materials were investigated using mist chemical vapor deposition (mist-CVD). The results showed that by adjusting the mixing ratios and volume ratios, thin films with desired optical and electrical properties can be obtained, which can be used as gate dielectric layers for metal-oxide-semiconductor field-effect transistors.
JOURNAL OF APPLIED PHYSICS
(2022)
Article
Physics, Applied
Tianshun Xie, Kazuki Fukuda, Mengnan Ke, Peter Krueger, Keiji Ueno, Gil-Ho Kim, Nobuyuki Aoki
Summary: This study presents a simple and controllable heavy doping method for 2H-MoTe2 crystal via high-density laser irradiation. The polarity of the doping can be controlled by changing the irradiation environment. Good performance with enhanced contact properties was achieved for MoTe2-nFET using the contact doping method via laser irradiation in a vacuum environment.
JAPANESE JOURNAL OF APPLIED PHYSICS
(2023)
Article
Physics, Multidisciplinary
Takemi Kato, Yongkai Li, Kosuke Nakayama, Zhiwei Wang, Seigo Souma, Fumihiko Matsui, Miho Kitamura, Koji Horiba, Hiroshi Kumigashira, Takashi Takahashi, Yugui Yao, Takafumi Sato
Summary: The study found that Nb substitution can increase the superconducting transition temperature and reduce the CDW temperature in Cs(V1-xNbx)(3)Sb-5. Nb substitution adjusts the position of the bands in the band structure, resulting in a decrease in the CDW gap and T-CDW. This study reveals the important role of the SP density of states in stabilizing the CDW, and suggests that the enhancement of superconductivity by Nb substitution is achieved through the expansion of the electron pocket and the recovery of the density of states at the Fermi level.
PHYSICAL REVIEW LETTERS
(2022)
Article
Physics, Applied
Yu Mizukoshi, Takumi Fukuda, Yuta Komori, Ryo Ishikawa, Keiji Ueno, Muneaki Hase
Summary: We investigated the ultrafast lattice dynamics in 1T-TiSe2 at room temperature using femtosecond reflection pump-probe and pump-pump-probe techniques. Time-domain signals and Fourier-transformed spectra revealed an A(1g) phonon mode at 5.9 THz. In addition, we observed an additional mode at approximately 3 THz, which corresponds to the charge-density wave (CDW) amplitude mode (AM) that is typically visible below T-c of approximately 200 K. We propose that the emergence of the CDW amplitude mode at room temperature may be a result of fluctuations of order parameters, supported by the suppression of the AM signal within an ultrafast timescale of approximately 0.5 ps in the pump-pump-probe experiment.
APPLIED PHYSICS LETTERS
(2023)
Article
Physics, Applied
Jessica Afalla, Joselito Muldera, Semmi Takamizawa, Takumi Fukuda, Keiji Ueno, Masahiko Tani, Muneaki Hase
Summary: Layered 2H-MoSe2 and 2H-WSe2 were investigated using terahertz (THz) time-domain emission spectroscopy. The THz emission exhibited an initial cycle due to surge currents and subsequent oscillations attributed to coherent interlayer phonon modes. By analyzing the THz emission waveforms and separating the contributions, the frequencies of the interlayer vibrations were determined. The fitting results revealed several vibrational modes in the range of 5.87-32.75 cm(-1), which were attributed to infrared-active interlayer shear and breathing modes. This study demonstrates the capability of THz emission spectroscopy in observing low-frequency vibrational modes in layered materials.
JOURNAL OF APPLIED PHYSICS
(2023)
Article
Chemistry, Multidisciplinary
Katsuaki Sugawara, Haruki Kusaka, Tappei Kawakami, Koki Yanagizawa, Asuka Honma, Seigo Souma, Kosuke Nakayama, Masashi Miyakawa, Takashi Taniguchi, Miho Kitamura, Koji Horiba, Hiroshi Kumigashira, Takashi Takahashi, Shin-ichi Orimo, Masayuki Toyoda, Susumu Saito, Takahiro Kondo, Takafumi Sato
Summary: Boron-based two-dimensional materials, especially rhombohedral boron monosulfide (r-BS), with its unique layered crystal structure, are being extensively studied for their potential applications in nanoelectronics. However, the analysis of the fundamental electronic properties of r-BS has been limited due to the lack of available large crystals. In this study, we utilize microfocused angle-resolved photoemission spectroscopy (micro-ARPES) to directly map the band structure of a tiny r-BS powder crystal, revealing that r-BS is a p-type semiconductor with an anisotropic in-plane effective mass and a band gap larger than 0.5 eV. These findings demonstrate the high applicability of micro-ARPES for investigating small powder crystals and provide new insights into the unexplored electronic states of novel materials.
Article
Nanoscience & Nanotechnology
Tappei Kawakami, Katsuaki Sugawara, Hirofumi Oka, Kosuke Nakayama, Ken Yaegashi, Seigo Souma, Takashi Takahashi, Tomoteru Fukumura, Takafumi Sato
Summary: This study reports on the unusual charge-density wave (CDW) in monolayer 2D VS2, which is associated with higher-order Fermi-surface nesting. The CDW exhibits a stripe pattern with periodicity of root 21R10.9 degrees root 3R30 degrees and opens an energy gap on the entire Fermi surface. The results suggest the involvement of a higher-order nesting vector 2q, twice as large as the normal nesting vector q, which is supported by anomalies in the calculated phonon dispersion and electronic susceptibility.
NPJ 2D MATERIALS AND APPLICATIONS
(2023)
Article
Chemistry, Multidisciplinary
Yasuaki Saruta, Katsuaki Sugawara, Hirofumi Oka, Tappei Kawakami, Takemi Kato, Kosuke Nakayama, Seigo Souma, Takashi Takahashi, Tomoteru Fukumura, Takafumi Sato
Summary: The current key challenge in 2D materials is to achieve emergent quantum phenomena in hetero structures by controlling the moire potential created by the periodicity mismatch between adjacent layers. This study demonstrates that the unstable octahedral MoTe2 can be stabilized in a commensurate MoTe2/graphene hetero-bilayer due to the moire potential between the two layers, providing a fresh approach to realize novel 2D quantum phases.
Article
Materials Science, Multidisciplinary
Koki Yanagizawa, Katsuaki Sugawara, Tappei Kawakami, Ryuichi Ando, Ken Yaegashi, Kosuke Nakayama, Seigo Souma, Kiyohisa Tanaka, Miho Kitamura, Koji Horiba, Hiroshi Kumigashira, Takashi Takahashi, Takafumi Sato
Summary: This study shows that monolayer titanium ditelluride's charge-density wave (CDW) can be switched conveniently by carrier tuning. The CDW appears only under certain conditions when partial Fermi-surface nesting occurs.
PHYSICAL REVIEW MATERIALS
(2023)
Article
Materials Science, Multidisciplinary
Thi Phuong Thao Nguyen, Kunihiko Yamauchi
Summary: In this paper, the anomalous Hall effect in the perovskite CaCrO3 is studied as a representative of collinear antiferromagnetic materials. It is found that the C-type antiferromagnetic ordering generates a sizable anomalous Hall conductivity. The enhanced effect is attributed to the spin splitting of Cr-3d bands induced by spin-orbit coupling near the Fermi energy.
Article
Materials Science, Multidisciplinary
Taiki Taguchi, Katsuaki Sugawara, Hirofumi Oka, Tappei Kawakami, Yasuaki Saruta, Takemi Kato, Kosuke Nakayama, Seigo Souma, Takashi Takahashi, Tomoteru Fukumura, Takafumi Sato
Summary: We discovered that monolayer 1T-NbTe2 is a new class of two-dimensional transition-metal dichalcogenide (TMD) with a star-of-David lattice similar to bulk TaS2 and isostructural monolayer NbSe2. It exhibits a metallic ground state characterized by the sparsely occupied star-of-David lattice with a lattice periodicity of (19x19). By using various techniques, we found that the hidden Fermi-surface nesting and associated CDW formation are the primary causes for this unique correlated metallic state without a Mott gap.
Article
Materials Science, Multidisciplinary
Kunihiko Yamauchi, Ikutaro Hamada
Summary: The effect of hydrogen doping on the crystal structure and electronic state of SmNiO3 was investigated using density functional theory. It was found that 50% hydrogen doping results in a stable atomic structure with insulating property. The stable structure exhibits a unique charge distribution pattern and Jahn-Teller distortion.
