Article
Chemistry, Multidisciplinary
Nemanja Peric, Yannick Lambert, Shalini Singh, Ali Hossain Khan, Nathali Alexandra Franchina Vergel, Dominique Deresmes, Maxime Berthe, Zeger Hens, Iwan Moreels, Christophe Delerue, Bruno Grandidier, Louis Biadala
Summary: Through experiments and calculations, it was found that individual CdSe nanoplatelets exhibit peaks instead of the typical step-like function associated with quantum wells, indicating restricted electron motion. This finding, along with the detection of deep trap states on the edge facets, provides insights into the lateral confinement in quantum wells with finite dimensions.
Article
Chemistry, Multidisciplinary
Tao Zhang, Chaofeng Gao, Dongdong Liu, Zhuolun Li, Hao Zhang, Mengqi Zhu, Zhenxiao Zhang, Puqin Zhao, Yingchun Cheng, Wei Huang
Summary: In this study, the evolution of van Hove singularities (vHSs) in twisted bilayer graphene (tBLG) under pressure was investigated using Raman spectroscopy. The results show that pressure induces a blue shift of specific spectral bands and tunes their intensity. Additionally, pressure enhances intervalley electron scattering. This study provides insights into the photon-electron-phonon interaction in tBLG and opens up avenues for pressure engineering of vHS in this material.
Article
Materials Science, Multidisciplinary
Xiaohan Liu, Xiaowei Huang, Peng Song, Chongze Wang, Liying Zhang, Peng Lv, Liangliang Liu, Weifeng Zhang, Jun-Hyung Cho, Yu Jia
Summary: A recent experiment has shown that alpha-MoB2, with a MgB2-type structure, exhibits superconductivity at -32 K under a pressure of 90 GPa, which is the highest transition temperature (Tc) among transition metal diborides. Researchers have used first-principles calculations to investigate the electronic properties of MoB2 and found that B atoms contribute significantly to electronic states near the Fermi level (EF), while the Mo dz2 orbital dominates in MoB2 and gives rise to double Van Hove singularities (VHS) in the density of states. The analysis suggests that these electronic states strongly interact with vibrational modes of Mo, leading to a large single gap and a Tc up to -37 K. Furthermore, by doping electrons into MoB2, the alignment of VHS with EF can be adjusted, resulting in an increased Tc of -43 K. These findings not only explain the high Tc observed in MoB2, but also highlight its potential as a platform for studying emergent strong electron-phonon coupling superconductivity associated with VHS.
Article
Chemistry, Multidisciplinary
Qian Gao, Qimin Yan, Zhenpeng Hu, Lan Chen
Summary: By using first-principles calculations, a bilayer Kagome lattice with multiple van Hove singularities is designed and a novel borophene (BK-borophene) with such lattice is proposed. The BK-borophene is predicted to be energetically, dynamically, thermodynamically, and mechanically stable. The electronic structure hosts both conventional and high-order van Hove singularities in one band.
Article
Multidisciplinary Sciences
Kyungchan Lee, Gunnar F. Lange, Lin-Lin Wang, Brinda Kuthanazhi, Thais Trevisan, Na Hyun Jo, Benjamin Schrunk, Peter P. Orth, Robert-Jan Slager, Paul C. Canfield, Adam Kaminski
Summary: Time reversal symmetric (TRS) invariant topological insulators (TIs) play a paradigmatic role in the field of topological materials, while weak topological insulators (WTIs) are more challenging due to their dependence on translational symmetry and limited topological surface states in specific directions. The discovery of a WTI state in RhBi2 opens up possibilities for novel quantum effects due to its exotic features.
NATURE COMMUNICATIONS
(2021)
Article
Chemistry, Multidisciplinary
Donghan Kim, Younsik Kim, Byungmin Sohn, Minsoo Kim, Bongju Kim, Tae Won Noh, Changyoung Kim
Summary: By utilizing an atomically ultra-thin SrRuO3 film, the electronic structure of a 2D van Hove singularity (VHS) is investigated and controlled using angle-resolved photoemission spectroscopy and transport properties. The 2D VHS and the sign of the charge carrier are precisely controlled by applying electric fields with alkali metal deposition and ionic-liquid gating methods. This tunable 2D VHS in an atomically flat oxide film could serve as a new strategy to achieve infinite density of states (DOS) near the Fermi level, enabling efficient tuning of electric properties.
ADVANCED MATERIALS
(2023)
Article
Chemistry, Physical
Liangguang Jia, Fei Gao, Yu Zhang, Yaoyao Chen, Baofei Hou, Zeping Huang, Quanzhen Zhang, Xu Wu, Liwei Liu, Shiwu Gao, Mads Brandbyge, Hong-Jun Gao, Yeliang Wang
Summary: This study reports the influence of defects in vdW crystals on the local atomic configurations and interlayer coupling. The findings show that Se vacancies in few-layer NbSe2 can cause atomic distortions and generate in-gap states in single-layer NbSe2. Moreover, these vacancies lead to a significant suppression of interlayer coupling in the bilayer system.
Article
Materials Science, Multidisciplinary
Yefan Tian, Yanglin Zhu, Rui Li, Zhiqiang Mao, Joseph H. Ross
Summary: The study used nuclear magnetic resonance spectroscopy to investigate the distinctive network of nodal lines in the Dirac semimetal ZrSiTe, revealing that the low-T behavior is dominated by a symmetry-protected nodal line with quasi-two-dimensional behavior. Additionally, a Van Hove singularity closely connected to this nodal line was identified, along with an associated T-induced Lifshitz transition.
Article
Chemistry, Multidisciplinary
Xutao Wang, Ningning Liu, Yanfu Wu, Yueqiao Qu, Wenxuan Zhang, Jinyue Wang, Dandan Guan, Shiyong Wang, Hao Zheng, Yaoyi Li, Canhua Liu, Jinfeng Jia
Summary: Metal-intercalated bilayer graphene has a high density of states near the Fermi energy, and thus is expected to exhibit enhanced strong correlation effect and superconductivity. By using a scanning tunneling microscope, researchers observed the superconducting energy gap and diamagnetic response in Ca-intercalated bilayer graphene, revealing strong coupling superconductivity and an isotropic s-wave superconductor.
Article
Materials Science, Multidisciplinary
Yu-Ping Lin, Rahul M. Nandkishore
Summary: The study investigates the interaction between real and imaginary charge density waves at the Van Hove singularity on hexagonal lattices. It reveals the formation of 3Q complex orders and the rich phase diagram they constitute. The theoretical model offers transparent interpretations of experimental observations in kagome metals and sheds light on the nature of topological charge density waves.
Article
Chemistry, Multidisciplinary
Qilong Wu, Meysam Bagheri Tagani, Lijie Zhang, Jing Wang, Yu Xia, Li Zhang, Sheng-Yi Xie, Yuan Tian, Long-Jing Yin, Wen Zhang, Alexander N. Rudenko, Andrew T. S. Wee, Ping Kwan Johnny Wong, Zhihui Qin
Summary: In this study, we demonstrate the electronic tuning ability at the WSe2/Au interface using twist engineering. By changing the twist angle, we are able to modulate the carrier doping in WSe2 from intrinsic p-type to n-type. We further achieve an n-p-n-type WSe2 homojunction by achieving a strong coupling interface. Additionally, we find that germanium intercalation can recover the intrinsic doping of WSe2. Our findings reveal the influence of twist angle and intercalation on interface doping.
Article
Materials Science, Multidisciplinary
Anirudh Chandrasekaran, Joseph J. Betouras
Summary: This study investigates the effect of disorder on systems with energy bands in two dimensions that have higher order Van Hove singularities (HOVHS). The authors utilize standard diagrammatic techniques for impurity averaging and analyze the signatures of these singularities in disordered systems. They find that while the divergence of the density of states (DOS) is smeared, the shape of the DOS is retained slightly away from the singularity, which may help understand experiments on materials that can host HOVHS. The impurity-induced smearing is calculated and the effects on electrical conductivity are studied.
Article
Multidisciplinary Sciences
Junyu Zong, Zhao-Yang Dong, Junwei Huang, Kaili Wang, Qi-Wei Wang, Qinghao Meng, Qichao Tian, Xiaodong Qiu, Yuyang Mu, Li Wang, Wei Ren, Xuedong Xie, Wang Chen, Yongheng Zhang, Can Wang, Fang-Sen Li, Shao-Chun Li, Jian-Xin Li, Hongtao Yuan, Yi Zhang
Summary: In this study, the van Hove singularity (VHS) in the epitaxial monolayer (ML) 1T-VSe2 film was successfully manipulated by the giant magnified dielectric constant er of SrTiO3(111) substrate with cooling, leading to a two-dimensional (2D) itinerant ferromagnetic state below 3.3 K. The manipulation of VHS was ascribed to the physical origin of the itinerant ferromagnetic state in ML 1T-VSe2, as supported by angle-resolved photoemission spectroscopy (ARPES) and theoretical analysis. These findings demonstrate the potential of controlling the ferromagnetic state in 2D systems through VHS engineering, expanding the application possibilities of 2D magnets for next-generation information technology.
Article
Physics, Multidisciplinary
Tran C. Phong, Nguyen T. Nam, Le T. T. Phuong
Summary: By tuning the filling fractions of van Hove singularities in PbBiI quantum spin Hall insulators through two mechanisms of C3v symmetry breaking – applying an in-plane magnetization exchange field and an inversion symmetry breaking field – we can induce exotic phenomena, including the formation of Weyl nodes in the electronic band structure and the deformation of bare van Hove singularities away from the Fermi energy. The above mechanisms also lead to the increase in the number of van Hove singularities due to the reconstruction of the Fermi surface. These findings propose two efficient mechanisms for tuning/creating van Hove singularities with potential applications in optoelectronics.
Article
Materials Science, Multidisciplinary
M. A. H. Haroon, M. A. H. Ahsanb
Summary: The T-shaped double quantum dot system with single-walled metallic armchair carbon nanotube leads was studied using Green functions obtained by the equation of motion method. The density of states of the carbon nanotube leads was found to play a significant role in determining the conductance profile, especially when the chemical potential of the isolated double quantum dot system aligned with a specific position in the density of states of the armchair carbon nanotube leads, leading to a considerable decrease in the height of the corresponding conductance peak.
CURRENT APPLIED PHYSICS
(2023)
Article
Multidisciplinary Sciences
Zhe Wang, Ignacio Gutierrez-Lezama, Dumitru Dumcenco, Nicolas Ubrig, Takashi Taniguchi, Kenji Watanabe, Enrico Giannini, Marco Gibertini, Alberto F. Morpurgo
Summary: This study shows how tunneling conductance can elucidate the material magnetic properties in atomically thin van der Waals materials. By measuring the temperature and magnetic field dependence of the conductance, the magnetic phase diagram of van der Waals materials can be mapped. The tunneling magnetoconductance in CrBr3 is found to depend exclusively on the magnetization M(H, T) over the entire temperature range, revealing a new approach to probe different properties of atomically thin ferromagnetic insulators related to their magnetization.
NATURE COMMUNICATIONS
(2021)
Article
Multidisciplinary Sciences
M. Michiardi, F. Boschini, H-H Kung, M. X. Na, S. K. Y. Dufresne, A. Currie, G. Levy, S. Zhdanovich, A. K. Mills, D. J. Jones, J. L. Mi, B. B. Iversen, Ph Hofmann, A. Damascelli
Summary: The study shows that the Rashba spin-splitting at the surface of Bi2Se3 topological insulator can be controlled via optical pulses, offering a new way to manipulate spin properties optically. By using time- and angle-resolved photoemission spectroscopy, it was demonstrated that optical excitation can tune the Rashba-induced spin splitting of a two-dimensional electron gas, potentially leading to optically-driven spin logic devices with improved performance.
NATURE COMMUNICATIONS
(2022)
Article
Materials Science, Multidisciplinary
D. J. Campbell, B. Wilfong, M. P. Zic, G. Levy, M. X. Na, T. M. Pedersen, S. Gorovikov, P. Y. Zavalij, S. Zhdanovich, A. Damascelli, E. E. Rodriguez, J. Paglione
Summary: This study presents a method for producing high quality KCo2As2 crystals and tests their properties. The experiments confirm the high quality and low impurity scattering of the crystals, and the absence of long range magnetic order. The compound exhibits unusual band dispersions and linear magnetoresistance.
PHYSICAL REVIEW MATERIALS
(2022)
Article
Chemistry, Multidisciplinary
Giulia Tenasini, David Soler-Delgado, Zhe Wang, Fengrui Yao, Dumitru Dumcenco, Enrico Giannini, Kenji Watanabe, Takashi Taniguchi, Christian Moulsdale, Aitor Garcia-Ruiz, Vladimir I. Fal'ko, Ignacio Gutierrez-Lezama, Alberto F. Morpurgo
Summary: We experimentally investigate the charge transfer and electric field effect at the interface of bilayer graphene and chromium trihalide. Our findings demonstrate the generation of a band gap in bilayer graphene due to charge transfer, and the gap size is determined by the conductivity and gate voltage dependence. The experimental results agree well with theoretical predictions and suggest the correlation of electrons in the chromium trihalide conduction band.
Article
Chemistry, Multidisciplinary
David Soler-Delgado, Fengrui Yao, Enrico Giannini, Dumitru Dumcenco, Jiaruo Li, Connor A. Occhialini, Riccardo Comin, Nicolas Ubrig, Alberto F. Morpurgo
Summary: We performed magnetotransport experiments on VI3 multilayers to investigate the relation between ferromagnetism in bulk and in exfoliated layers. The experiments showed that the Curie temperature of exfoliated multilayers is higher than in bulk, and an unusual evolution of tunneling magnetoconductance was observed at low temperatures, similar to the phenomenology observed in bulk. Comparing the magneto-conductance measured for different field orientations confirmed that the easy-axis orientation in multilayers is similar to that in bulk, and suggested different in-plane magnetization directions in different layers. These results demonstrate the similarity of magnetic states between bulk and multilayers, and highlight the complementarity of magnetotransport and magneto-optical measurements in probing magnetism in 2D materials.
Correction
Multidisciplinary Sciences
M. Michiardi, F. Boschini, H. -H. Kung, M. X. Na, S. K. Y. Dufresne, A. Currie, G. Levy, S. Zhdanovich, A. K. Mills, D. J. Jones, J. L. Mi, B. B. Iversen, Ph. Hofmann, A. Damascelli
NATURE COMMUNICATIONS
(2022)
Article
Multidisciplinary Sciences
A. C. Qu, P. Nigge, S. Link, G. Levy, M. Michiardi, P. L. Spandar, T. Matthe, M. Schneider, S. Zhdanovich, U. Starke, C. Gutierrez, A. Damascelli
Summary: Quantum materials, like graphene, are highly influenced by their environments. A recent study has shown that a small concentration of surface atoms can trigger a global Kekule density wave phase in graphene, resulting in the opening of an energy gap. This discovery highlights the unexpected sensitivity of the graphene lattice to dilute surface disorder and suggests a new approach for designing novel phases in two-dimensional materials.
Article
Materials Science, Multidisciplinary
Wenliang Zhang, Clio Efthimia Agrapidis, Yi Tseng, Teguh Citra Asmara, Eugenio Paris, Vladimir N. Strocov, Enrico Giannini, Satoshi Nishimoto, Krzysztof Wohlfeld, Thorsten Schmitt
Summary: This study investigates the evolution of spin excitations in hole-doped superconducting cuprates and confirms the close connection between spin excitations and short-range magnetic correlations.
NPJ QUANTUM MATERIALS
(2022)
Article
Chemistry, Multidisciplinary
Dominik Rau, Jasmin Jandke, Fang Yang, Wulf Wulfhekel, Christophe Berthod, Khalil Zakeri
Summary: Spin-orbit coupling (SOC) is a fundamental physical interaction that describes the coupling between electron spin and orbital motion. In this study, we performed spectroscopy experiments on a FeSe monolayer on strontium titanate, a two-dimensional high-temperature superconductor, and found that the scattering cross-section is spin dependent. We showed that the SOC in this system is strong and may have important implications for the electronic structures and the mechanism of superconductivity.
Article
Multidisciplinary Sciences
Bastien Michon, Christophe Berthod, Carl Willem Rischau, Amirreza Ataei, Lu Chen, Seiki Komiya, Shimpei Ono, Louis Taillefer, Dirk van der Marel, Antoine Georges
Summary: In this paper, researchers experimentally demonstrated the universal scaling properties of resistivity, optical conductivity, and optical effective mass of La2-xSrxCuO4 as a function of frequency and temperature. They also proposed a new theoretical framework to describe the unique properties of quantum critical matter.
NATURE COMMUNICATIONS
(2023)
Article
Multidisciplinary Sciences
Fengrui Yao, Volodymyr Multian, Zhe Wang, Nicolas Ubrig, Jeremie Teyssier, Fan Wu, Enrico Giannini, Marco Gibertini, Ignacio Gutierrez-Lezama, Alberto F. Morpurgo
Summary: This study reports the observation of three distinct magnetic phases in exfoliated CrBr3 multilayers and reveals that the uniaxial anisotropy in CrBr3 is significantly smaller than in CrI3. These findings provide important information on the stacking-dependent interlayer exchange energy and establish CrBr3 as an ideal system for creating non-collinear magnetic phases.
NATURE COMMUNICATIONS
(2023)
Article
Materials Science, Multidisciplinary
Khalil Zakeri, Christophe Berthod
Summary: This paper extends the theory of low-energy electron scattering by including spin-orbit coupling. The impact of this interaction on the scattering cross section is discussed, particularly for a spin-polarized electron beam scattered from nonmagnetic surfaces with strong spin-orbit coupling. An expression for the scattering cross section is derived under certain assumptions, which can be used for numerical calculations of spin-polarized spectra recorded by spin-polarized high-resolution electron energy-loss spectroscopy experiments.
Article
Chemistry, Multidisciplinary
Dorota Pulmannova, Celine Besnard, Petr Bezdicka, Marios Hadjimichael, Jeremie Teyssier, Enrico Giannini
Summary: Single crystals of transition metal oxides are crucial for studying their physical properties. In the strontium titanate family, crystal growth of all compounds except SrTiO3 has been challenging. This study successfully grew crystals of the high-temperature polymorph of Sr2TiO4 and investigated its crystal structure and transformation mechanism, providing insights into the failed growth of the low-temperature phase.
Article
Physics, Multidisciplinary
Christophe Berthod, Haijing Zhang, Alberto F. Morpurgo, Thierry Giamarchi
Summary: This study uses linear-response theory to describe the capacitance of two coupled electron liquids and provides a general expression for capacitance involving intra- and interlayer electronic polarizabilities. The research shows that the cross quantum capacitance effects can significantly impact the capacitance, especially in cases of very small electrode separation.
PHYSICAL REVIEW RESEARCH
(2021)
Article
Materials Science, Multidisciplinary
M. X. Na, F. Boschini, A. K. Mills, M. Michiardi, R. P. Day, B. Zwartsenberg, G. Levy, S. Zhdanovich, A. F. Kemper, D. J. Jones, A. Damascelli
