Article
Physics, Multidisciplinary
P. A. Igoshev, V. Yu Irkhin
Summary: This study discovers and classifies all van Hove singularities in the density of states of a face-centered cubic lattice, with a focus on higher-order singularities. Giant singularities, formed by van Hove lines or surfaces, occur at specific values of the ratio between nearest and next-nearest neighbor hopping integrals. An exact formula for the density of states, allowing efficient numerical implementation, is proposed. The standard tetrahedron method is shown to be inadequate due to poor convergence near van Hove singularities. A comparison with a high-dimensional case, including next nearest neighbors, is also performed.
Article
Physics, Multidisciplinary
Shuigang Xu, Mohammed M. Al Ezzi, Nilanthy Balakrishnan, Aitor Garcia-Ruiz, Bonnie Tsim, Ciaran Mullan, Julien Barrier, Na Xin, Benjamin A. Piot, Takashi Taniguchi, Kenji Watanabe, Alexandra Carvalho, Artem Mishchenko, A. K. Geim, Vladimir I. Fal'ko, Shaffique Adam, Antonio Helio Castro Neto, Kostya S. Novoselov, Yanmeng Shi
Summary: The study of electronic transport properties of twisted monolayer-bilayer graphene reveals highly tunable van Hove singularities that can cause strong correlation effects under optimum conditions by changing the twist angle or applying an electric field. This demonstrates the potential for correlated insulating states in a structure of monolayer and bilayer graphene with a small twist between them.
Article
Chemistry, Physical
Shuang Wu, Zhenyuan Zhang, K. Watanabe, T. Taniguchi, Eva Y. Andrei
Summary: In magic-angle twisted bilayer graphene, doping-induced Lifshitz transitions and van Hove singularities lead to the emergence of correlation-induced gaps and topologically non-trivial subbands. With the presence of a magnetic field, quantized Hall plateaus reveal the subband topology and signal the emergence of Chern insulators with Chern numbers. Additionally, a van Hove singularity at a filling of 3.5 suggests the possibility of a fractional Chern insulator, accompanied by a crossover from low-temperature metallic to high-temperature insulating behavior.
Article
Multidisciplinary Sciences
Yong Hu, Xianxin Wu, Yongqi Yang, Shunye Gao, Nicholas C. Plumb, Andreas P. Schnyder, Weiwei Xie, Junzhang Ma, Ming Shi
Summary: This study reveals the existence of topologically Dirac surface states (TDSSs) in the magnetic kagome material GdV6Sn6 and successfully manipulates the TDSSs and van Hove singularities (VHSs). These results provide a significant platform for studying the nontrivial topology, magnetism, and correlation effects in kagome lattices.
Article
Materials Science, Multidisciplinary
J. Ebad-Allah, A. A. Tsirlin, Y. L. Zhu, Z. Q. Mao, C. A. Kuntscher
Summary: We conducted a temperature-dependent infrared spectroscopy study on the layered topological semimetal Nb3SiTe6 and performed density-functional theory calculations to investigate its electronic band structure and optical conductivity. Our results showed an anisotropic behavior of the in-plane optical conductivity, with three prominent excitations located at around 0.15, 0.28, and 0.41 eV when the incident radiation was polarized along the c axis. These excitations were well reproduced in the theoretical spectra. Based on the ab initio results, we interpreted the excitations around 0.15 and 0.28 eV as fingerprints of van Hove singularities in the electronic band structure and compared them to findings in other topological semimetals.
Article
Materials Science, Multidisciplinary
Hyeong Jun Lee, Choong H. Kim, Ara Go
Summary: In this study, a systematic investigation was conducted on the interplay between van Hove singularities and Hund's metallicity, demonstrating a significant enhancement of the latter by the former. The results suggest a synergy between van Hove singularities and Hund's coupling, providing valuable insights into the amplification of correlation-induced phenomena in crystalline solids.
Article
Materials Science, Multidisciplinary
Harrison LaBollita, Antia S. Botana
Summary: The electronic structure of the new family of kagome metals AV(3)Sb(5) can be modified by pressure and hole doping, with pressure shifting saddle points away from the Fermi level and doping bringing them closer. This demonstrates how pressure and doping can be used to tune Fermi surface instabilities and associated orders.
Article
Physics, Multidisciplinary
Yin-Xiang Li, Xiao-Tong Yang
Summary: In this study, we found that Ni-based transition-metal trichalcogenides exhibit a suppression of chiral even-parity d + id-wave (E-g) state by odd-parity p + ip-wave (E-u) state when approaching the type-II van Hove singularities. The type-II van Hove singularities peak in density of states strengthens ferromagnetic fluctuation, leading to triplet pairing. The competition between antiferromagnetic and ferromagnetic fluctuation results in a pairing phase transition from singlet to triplet pairing in these materials.
FRONTIERS OF PHYSICS
(2021)
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
Materials Science, Multidisciplinary
Ina Marie R. Verzola, Rovi Angelo B. Villaos, Winda Purwitasari, Zhi-Quan Huang, Chia-Hsiu Hsu, Guoqing Chang, Hsin Lin, Feng-Chuan Chuang
Summary: This study systematically investigates the stability, electronic properties, and topological characteristics of Re-based transition metal dichalcogenides. The research reveals that these materials exhibit highly tunable properties, excellent thermoelectric performance, and potential for spintronics applications.
MATERIALS TODAY COMMUNICATIONS
(2022)
Article
Chemistry, Multidisciplinary
Liyue Xu, Yu Xu, Yipu Qu, Bing Cao, Chinhua Wang, Ke Xu
Summary: By growing GaN films on 2D materials like h-BN, the defects and stress caused by lattice and thermal mismatch can be reduced, resulting in improved crystal quality of GaN.
CRYSTAL GROWTH & DESIGN
(2023)
Article
Engineering, Environmental
Xuewen Jiang, Jiahao Lv, Zibin Chen, Zhonghui Shen, Jian Wang, Zhao Deng, Minghe Cao, Zhonghua Yao, Shujun Zhang, Hanxing Liu, Hua Hao
Summary: An effective route to improve energy storage performance is by constructing polymorphic nanostructures. The appropriate volume fraction of amorphous/crystalline structure is confirmed to be conducive to energy storage properties. Mn dopant in the 0.94BT-0.06BZZ films induces higher polarization and leads to a high energy density and improved energy efficiency. The confirmation of amorphous structure and local polymorphic nanostructures using aberration-corrected scanning transmission electron microscopy contributes significantly to enhanced energy storage properties and provides a new design paradigm for high-performance dielectric materials.
CHEMICAL ENGINEERING JOURNAL
(2022)
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
Chemistry, Multidisciplinary
Julian Klein, Benjamin Pingault, Matthias Florian, Marie-Christin Heissenbuettel, Alexander Steinhoff, Zhigang Song, Kierstin Torres, Florian Dirnberger, Jonathan B. Curtis, Mads Weile, Aubrey Penn, Thorsten Deilmann, Rami Dana, Rezlind Bushati, Jiamin Quan, Jan Luxa, Zdenek Sofer, Andrea Alu, Vinod M. Menon, Ursula Wurstbauer, Michael Rohlfing, Prineha Narang, Marko Loncar, Frances M. Ross
Summary: In this study, it was found that the magnetic semiconductor CrSBr behaves like a quasi-1D material in a magnetically ordered environment. The strong 1D electronic character of CrSBr originates from the Cr-S chains and the weak interlayer hybridization, leading to anisotropy in effective mass and dielectric screening. Moreover, CrSBr hosts spectrally narrow excitons of high binding energy and oscillator strength due to reduced dimensionality and interlayer coupling. Overall, CrSBr is an experimentally attractive candidate for the study of exotic exciton and 1D-correlated many-body physics.
Article
Physics, Condensed Matter
Tran C. Phong, Le T. T. Phuong
Summary: In this study, we investigate the effect of gas molecule doping on the electronic properties of single-layer beta(12)-borophene. We find that van Hove singularities are significantly generated and that the material exhibits different phases depending on the type of atoms doped with gas molecules. We also observe a gapless semiconducting phase in certain doping configurations. These findings have implications for the development of gas sensors based on field-effect transistors.
PHYSICA B-CONDENSED MATTER
(2023)
Article
Physics, Applied
Jona Gruembel, Rudiger Goldhahn, Dae-Woo Jeon, Martin Feneberg
Summary: The Raman excitations of an alpha-Ga2O3 thin film were investigated, and the contributions of different decay mechanisms to the phonon modes were quantified through model calculations. The experimental data can be well described by the applied theoretical models, and the phonon modes of alpha-Ga2O3 show smaller frequency shifts and broadening under temperature variation compared to other materials.
APPLIED PHYSICS LETTERS
(2022)
Article
Chemistry, Inorganic & Nuclear
Sida Wang, Phil Liebing, Felix Engelhardt, Liane Hilfert, Sabine Busse, Ruediger Goldhahn, Frank T. Edelmann
Summary: A series of new homoleptic first-row transition metal and yttrium tris(alkynylamidinate) complexes have been synthesized and characterized. A novel unsolvated lithium amidinate compound was isolated and structurally characterized. Two new potassium cyclopropylethinylamidinates were prepared by nucleophilic addition reactions. The metal complexes were readily obtained by reactions of metal precursors with the alkali metal cyclopropylethinylamidinates. An alternative synthetic route to a titanium(III) complex was discovered. The compounds were fully characterized using analytical and spectroscopic methods.
ZEITSCHRIFT FUR ANORGANISCHE UND ALLGEMEINE CHEMIE
(2022)
Article
Materials Science, Multidisciplinary
Sandhya Chandola, Simone Sanna, Conor Hogan, Eugen Speiser, Julian Plaickner, Norbert Esser
Summary: This article investigates the effect of atomic hydrogen and toluene-3,4-dithiol (TDT) adsorption on the quasi-1D structures of the Si(553)-(5 x 2)-Au reconstruction. The results provide insights into the optical responses of the surface and explain the origin of the spectral modifications caused by the adsorbate exposure. The preferential adsorption at step edges induces charge transfer and modifies the electronic structure.
PHYSICA STATUS SOLIDI-RAPID RESEARCH LETTERS
(2022)
Article
Engineering, Electrical & Electronic
Shaojun Wu, Martin Guttmann, Neysha Lobo-Ploch, Frank Gindele, Norman Susilo, Arne Knauer, Tim Kolbe, Jens Rass, Sylvia Hagedorn, Hyun Kyong Cho, Katrin Hilbrich, Martin Feneberg, Ruediger Goldhahn, Sven Einfeldt, Tim Wernicke, Markus Weyers, Michael Kneissl
Summary: The increase in light extraction efficiency and total output power of UV LEDs after encapsulation with UV-transparent silicone are studied. The simulations and experimental results show that properly placed hemispherical encapsulation can enhance the light extraction efficiency and increase the total output power of the LEDs.
SEMICONDUCTOR SCIENCE AND TECHNOLOGY
(2022)
Article
Chemistry, Physical
Vitaly Gorelov, Lucia Reining, Martin Feneberg, Ruediger Goldhahn, Andre Schleife, Walter R. L. Lambrecht, Matteo Gatti
Summary: This article uses V2O5 as an example to explore how charge-transfer excitations combine to form excitons with large binding energy and electron-hole distance, and explains this phenomenon. By combining various methods, consistent results are obtained.
NPJ COMPUTATIONAL MATERIALS
(2022)
Article
Chemistry, Inorganic & Nuclear
Sida Wang, Phil Liebing, Felix Engelhardt, Liane Hilfert, Sabine Busse, Ruediger Goldhahn, Frank T. Edelmann
Summary: The current library of amidinate ligands has been expanded by synthesizing two novel dimethylamino-substituted alkynylamidinate anions. These compounds were used to study initial complexation reactions with selected transition metals.
ZEITSCHRIFT FUR ANORGANISCHE UND ALLGEMEINE CHEMIE
(2023)
Article
Physics, Applied
Kingsley Egbo, Esperanza Luna, Jonas Laehnemann, Georg Hoffmann, Achim Trampert, Jona Gruembel, Elias Kluth, Martin Feneberg, Ruediger Goldhahn, Oliver Bierwagen
Summary: By combining SnO2 and Sn, we successfully grew phase-pure single-crystalline metastable SnO (001) thin films on Y-stabilized ZrO2 (001) substrates using suboxide molecular beam epitaxy (S-MBE) at a growth rate of about 1.0 nm/min without additional oxygen. These films exhibit epitaxial growth over a wide temperature range of 150 to 450°C. The obtained p-type SnO films at low substrate temperatures show promise for back-end-of-line (BEOL) compatible applications and integration with n-type oxides in pn heterojunctions and field-effect transistors.
JOURNAL OF APPLIED PHYSICS
(2023)
Article
Physics, Applied
Elias Kluth, Michael Fay, Christopher Parmenter, Joseph Roberts, Emily Smith, Craig Stoppiello, Fabien Massabuau, Ruediger Goldhahn, Martin Feneberg
Summary: This study investigates the redshift of the absorption onset and amplitude increase in the ultraviolet complex dielectric function (DF) of corundum-like a-(TixGa1-x)(2)O-3 with increasing Ti content. a-Ga2O3 thin film samples alloyed with Ti up to x = 0.61 are grown using plasma enhanced atomic layer deposition, and characterized using ultraviolet spectroscopic ellipsometry, transmission electron microscopy, and x-ray photoelectron spectroscopy (XPS). The results show that the samples remain crystalline up to x = 0.053. Ellipsometry reveals a strong red shift in the absorption onset and an increase in amplitude with increasing Ti content, attributed to the successive occupation of Ti-related 3d states in the density-of-states. Valence band XPS results suggest that the red shift is mainly due to conduction band lowering rather than the valence band.
APPLIED PHYSICS LETTERS
(2023)
Article
Chemistry, Inorganic & Nuclear
Sida Wang, Phil Liebing, Martin Feneberg, Farid M. Sroor, Felix Engelhardt, Liane Hilfert, Sabine Busse, Elias Kluth, Rudiger Goldhahn, Frank T. Edelmann
Summary: A series of new alkynylamidinate complexes of selected first and second row transition metals has been synthesized and fully characterized. Different reactions were employed to obtain various binuclear complexes with different metal-metal bonding. The structures of all the compounds were determined using single-crystal X-ray diffraction and spectroscopic techniques.
EUROPEAN JOURNAL OF INORGANIC CHEMISTRY
(2023)
Article
Physics, Applied
M. Ries, E. Poliani, F. Nippert, D. Seidlitz, L. T. H. Greif, I. Koslow, J. Blaesing, M. Auf der Maur, A. Hoffmann, N. Esser, M. R. Wagner
Summary: In this study, the electronic and optical properties of InGaN single quantum wells with thin GaN cap-layers were investigated. A significant spectral shift of quantum well emission was observed for cap-layer thicknesses between 1 and 10 nm. The origin of this shift was explained by calculations and the influence of alloy fluctuations and homogeneity was studied on both the microscale and nanoscale using UV micro-Raman scattering and TERS. The results demonstrated the capabilities of TERS to resolve nanoscale thickness fluctuations and compositional inhomogeneities in ultra-thin semiconductor layers.
JOURNAL OF APPLIED PHYSICS
(2023)
Article
Biochemistry & Molecular Biology
Nicole Harmgarth, Phil Liebing, Volker Lorenz, Felix Engelhardt, Liane Hilfert, Sabine Busse, Ruediger Goldhahn, Frank T. Edelmann
Summary: This paper describes the synthesis of the first amidinate and amidine derivatives of p-carborane. The compounds were obtained through double lithiation of p-carborane followed by treatment with diorganocarbodiimides and chlorotrimethylsilane. The new compounds were characterized by X-ray diffraction.
Article
Physics, Applied
Elias Baron, Ruediger Goldhahn, Shirly Espinoza, Martin Zahradnik, Mateusz Rebarz, Jakob Andreasson, Michael Deppe, Donat J. As, Martin Feneberg
Summary: We have published a recent study on femtosecond pump-probe absorption edge spectroscopy of cubic GaN, which resulted in the transient dielectric function. In this study, we investigate the time-dependent transition energy between the conduction and valence bands by analyzing pump-probe measurements. By converting transition energies into free-carrier concentrations and assuming electron contributions to be dominant, we model the ultra-fast change and consider various effects such as relaxation, recombination, diffusion, gain-recombination, and temperature effects. Both models provide similar values for the characteristic relaxation time, recombination time, and diffusion coefficient.
JOURNAL OF APPLIED PHYSICS
(2023)
Article
Physics, Applied
Elias Baron, Rudiger Goldhahn, Shirly Espinoza, Martin Zahradnik, Mateusz Rebarz, Jakob Andreasson, Michael Deppe, Donat J. J. As, Martin Feneberg
Summary: An ultra-fast change in the absorption onset of zincblende gallium-nitride (zb-GaN) is observed using time-dependent femtosecond pump-probe spectroscopic ellipsometry. The absorption onset increases due to band filling, while the bandgap decreases due to bandgap renormalization. The optical properties vary from the sample surface to the substrate, which is taken into account by grading analysis.
JOURNAL OF APPLIED PHYSICS
(2023)
Article
Chemistry, Inorganic & Nuclear
Ryan Johnson, Phil Liebing, Daniel P. Musikanth, Stuart A. Regitz, Donna S. Amenta, Ruediger Goldhahn, Frank T. Edelmann, John W. Gilje
Summary: The syntheses of two new ligands, L1 and L2, and their complexation with palladium(II) were investigated. L1 was best prepared using a Cs2CO3 catalyzed Michael addition, while L2 was synthesized catalyst- and solvent-free. Both ligands reacted with PdCl2(COD) to form the corresponding complexes. Crystal structures of the complexes were determined. An isomerization process was observed in complex 4. The ease of preparation and high yields make L1 and L2 potentially useful for further studies.
ZEITSCHRIFT FUR ANORGANISCHE UND ALLGEMEINE CHEMIE
(2023)
Article
Chemistry, Inorganic & Nuclear
Volker Lorenz, Phil Liebing, Matthias Mueller, Liane Hilfert, Martin Feneberg, Elias Kluth, Marcel Kuehling, Magnus R. Buchner, Rudiger Goldhahn, Frank T. Edelmann
Summary: A series of brightly colored alkaline earth metal 1,3-dimethylviolurates have been synthesized and characterized. Different colored salts were obtained by neutralizing 1,3-dimethylvioluric acid monohydrate with corresponding metal dihydroxides. The study also discovered new compound structures and mixed-anion salts, expanding the coordination chemistry of violurates and related ligands.
DALTON TRANSACTIONS
(2022)