Article
Chemistry, Physical
Byungmin Sohn, Eunwoo Lee, Se Young Park, Wonshik Kyung, Jinwoong Hwang, Jonathan D. Denlinger, Minsoo Kim, Donghan Kim, Bongju Kim, Hanyoung Ryu, Soonsang Huh, Ji Seop Oh, Jong Keun Jung, Dongjin Oh, Younsik Kim, Moonsup Han, Tae Won Noh, Bohm-Jung Yang, Changyoung Kim
Summary: Magnetism and spin-orbit coupling play crucial roles in topological transport phenomena in itinerant ferromagnets. Two-dimensional systems may have stable nodal structures, and perovskite oxides generally support symmetry-protected nodal lines and points in their spin-polarized band structures.
Article
Multidisciplinary Sciences
Benjamin Schrunk, Yevhen Kushnirenko, Brinda Kuthanazhi, Junyeong Ahn, Lin-Lin Wang, Evan O'Leary, Kyungchan Lee, Andrew Eaton, Alexander Fedorov, Rui Lou, Vladimir Voroshnin, Oliver J. Clark, Jamie Sanchez-Barriga, Sergey L. Bud'ko, Robert-Jan Slager, Paul C. Canfield, Adam Kaminski
Summary: The Fermi surface plays a crucial role in material properties. Fermi arcs can be signatures of unusual electronic states and can be obtained by breaking specific symmetries. In this study, experimental evidence is presented showing the emergence of hole- and electron-like Fermi arcs below the Neel temperature in an antiferromagnetic state. This magnetic splitting effect is unique as it creates bands with opposing curvature that change with temperature.
Review
Physics, Applied
Cheng Zhang, Yi Zhang, Hai-Zhou Lu, X. C. Xie, Faxian Xiu
Summary: This Perspective discussed the Weyl orbit in the context of topological semimetals, focusing on its role in the 3D quantum Hall effect and potential new phenomena. The Weyl orbit is a new type of cyclotron orbit proposed in Weyl semimetals with surface-bulk hybrid properties. Recent experiments using the Weyl orbit have led to advancements in understanding higher-dimension quantum Hall physics and exploring new applications in topological quantum states.
NATURE REVIEWS PHYSICS
(2021)
Article
Physics, Multidisciplinary
Maxim Breitkreiz, Piet W. Brouwer Dahlem
Summary: We predict a new metallic state of matter in a spatially varying Weyl-semimetal superstructure. This state exhibits stretched Weyl nodes that form extended, anisotropic Fermi surfaces made up of Fermi arc-like states. Unlike the parental Weyl semimetal, the ultraquantum state, where the anomalous chiral Landau level is the only state at the Fermi energy, is reached for a finite energy window at zero magnetic field in this Fermi-arc metal. The dominance of the ultraquantum state leads to a universal low-field ballistic magnetoconductance and the absence of quantum oscillations.
PHYSICAL REVIEW LETTERS
(2023)
Article
Physics, Multidisciplinary
Kevin A. A. Reiss, David K. K. Campbell
Summary: Classical statistical mechanics has relied on assumptions such as the equipartition theorem, but the validity of these assumptions has been questioned. This paper performs a broad analysis of a metastable state in the classical FPUT models and proposes a measure called spectral entropy to quantify the distance from equipartition. The authors also explore the behavior of the metastable state in different FPUT models and compare the results to other models.
Article
Chemistry, Physical
Alan J. J. Ardell
Summary: This article critically reviews the data on the equilibrium solubilities of the alpha AlLi solid solution phase and the ordered metastable delta' Al3Li precipitate phase, and proposes a new binary alloy phase diagram. The equations for the equilibrium solubilities of Li in the alpha and delta' phases are derived. The new phase diagram is based on extensive re-analysis of previously published data, including additional data not considered before, and excludes non-equilibrium data.
JOURNAL OF PHASE EQUILIBRIA AND DIFFUSION
(2023)
Article
Optics
Dmitry A. Zezyulin, Yaroslav Kartashov, Vladimir V. Konotop
Summary: A two-dimensional nonlinear waveguide with distributed gain and losses is studied, where the system consists of an unperturbed complex potential and a small nonseparable perturbation. The system features an exceptional point in its spectrum, driving it into the unbroken phase and resulting in stable propagation of two-component envelope solitons. In the original model, taking both traverse directions into account leads to metastable two-component bright solitons that persist over long propagation distances.
Article
Materials Science, Multidisciplinary
Jie Chen, Hang Li, Tengyu Guo, Peng Chen, Dongfeng Zheng, Guoqiang Yu, Yong-Chang Lau, Xuekui Xi, Wenhong Wang
Summary: We report an unusual change in the anomalous anisotropic magnetoresistance (AMR) effect in HoPtBi, where the AMR transitions from quasi-twofold to fourfold symmetry and forms a stable rotated fourfold symmetry with increasing magnetic fields. The 3D mapping experiments confirm that it is an intrinsic 3D effect. Fourier transformation analysis indicates that the superposition of C-2, C-4, and C-6 signals with phase angle transitions leads to the novel AMR. By combining the band structures and AMR features, we evaluate the possible origin of the symmetry rotation and attribute it to the topological band change. This work provides insight into the anomalous AMR effect of topological materials and has implications for understanding the evolution of topological bands in a magnetic field. We propose that other rare-earth half-Heusler alloys can potentially exhibit similar phenomena.
NPG ASIA MATERIALS
(2023)
Article
Multidisciplinary Sciences
Thomas Hartke, Botond Oreg, Carter Turnbaugh, Ningyuan Jia, Martin Zwierlein
Summary: The Hubbard model of attractively interacting fermions is used to study fermion pairing. In this model, a crossover between tightly bound pairs and long-range Cooper pairs occurs, with a pseudo-gap region above the superfluid critical temperature. By directly observing a Hubbard lattice gas of fermionic potassium-40 atoms under a bilayer microscope, the nonlocal nature of fermion pairing is revealed. The study also provides insights into the pseudo-gap behavior in strongly correlated fermion systems.
Article
Multidisciplinary Sciences
Daniele Guerci, Jie Wang, Jiawei Zang, Jennifer Cano, Andrew Millis
Summary: We theoretically investigate the interaction between magnetism and a heavy Fermi liquid in the AB-stacked transition metal dichalcogenide bilayer system MoTe2/WSe2. The interlayer electron transfer leads to a chiral Kondo exchange, resulting in a strong dependence of the Kondo temperature on carrier concentration and anomalous Hall effect due to topological hybridization gap. Our findings provide concrete experimental predictions for ongoing experiments on MoTe2/WSe2 bilayer heterostructures and offer a controlled route to observe a topological selective Mott transition.
Article
Chemistry, Multidisciplinary
Yongping Fu
Summary: This article describes the polymorphism in lead halide perovskites, focusing on the stabilization of metastable perovskite lattices in the 2D limit and the influence of A-cations on structural, optoelectronic, and ferroelectric properties. Future perspectives on structure exploration and studies of fundamental photophysical properties using stabilized perovskite lattices are also provided.
ADVANCED MATERIALS
(2022)
Article
Multidisciplinary Sciences
Orion Ciftja
Summary: This study investigates the stability of the circular Fermi surface of a two-dimensional electron gas system against elliptical deformation induced by anisotropic Coulomb interaction, finding the lowest energy phase to be one with optimal elliptical deformation.
SCIENTIFIC REPORTS
(2021)
Article
Materials Science, Multidisciplinary
R. Eder, P. Wrobel
Summary: This paper discusses the two-channel Kondo lattice model, in which a single localized spin per unit cell is coupled to two different conduction electron orbitals per unit cell. The calculations are done using the bond fermion formalism. It is found that for a Hamiltonian symmetric under exchange of the conduction channels, there is a spontaneous breaking of this symmetry, with the Kondo singlets being formed predominantly between the localized spin and only one of the two conduction orbitals. In addition to a channel-ferromagnetic phase, a channel-antiferromagnetic phase is also identified where the preferred conduction electron orbital alternates between sublattices. The parameter determining the transition between these phases is the interchannel hybridization.
Article
Materials Science, Multidisciplinary
Arunava Kar, Arpan Das, Smruti Ranjan Mohanty, Shobhana Narasimhan, Krishnakumar S. R. Menon
Summary: The study investigates the evolution of atomic structure and electronic band dispersion of oxygen-induced superstructures on the Mo(110) surface using various techniques and theory. Results show that oxygen adsorption at elevated temperatures leads to the elimination of mixed-phase coexisting regions observed at room temperature, and the appearance of three distinct superstructures. Oxygenation of the surface induces a confinement-induced gaplike opening at the zone center, which can be tuned by the overlayer oxygen coverage.
Article
Optics
Yijia Zhou, Rejish Nath, Haibin Wu, Igor Lesanovsky, Weibin Li
Summary: The study theoretically investigates the deformation of the Fermi surface of three-dimensional gas of Rydberg-dressed Li-6 atoms, showing that the dressed interactions can drastically modify the shape of the Fermi surface depending on the interplay between Fermi momentum and reciprocal momentum. Complex deformations with multipolar characteristics are encountered when the Fermi momentum is greater than or equal to the characteristic soft-core radius of the dressing-induced potential. The analysis also demonstrates the potential for Rydberg dressing to high angular momentum states in investigating unconventional Fermi gases and multiwave superconductivity.
Article
Physics, Multidisciplinary
Hannah C. Robarts, Thomas E. Millichamp, Daniel A. Lagos, Jude Laverock, David Billington, Jonathan A. Duffy, Daniel O'Neill, Sean R. Giblin, Jonathan W. Taylor, Grazyna Kontrym-Sznajd, Malgorzata Samsel-Czekala, Hongbin Bei, Sai Mu, German D. Samolyuk, G. Malcolm Stocks, Stephen B. Dugdale
PHYSICAL REVIEW LETTERS
(2020)
Article
Materials Science, Multidisciplinary
C. J. Sayers, L. S. Farrar, S. J. Bending, M. Cattelan, A. J. H. Jones, N. A. Fox, G. Kociok-Kohn, K. Koshmak, J. Laverock, L. Pasquali, E. Da Como
PHYSICAL REVIEW MATERIALS
(2020)
Article
Physics, Multidisciplinary
Jans Henke, Felix Flicker, Jude Laverock, Jasper van Wezel
Article
Chemistry, Physical
Wenhan Chen, A. D. N. James, S. B. Dugdale
Summary: The Fermi surface topology is important for the macroscopic properties of metals and can be sensitive to electron correlation. By comparing the results of density functional theory (DFT) and the combination of DFT with dynamical mean field theory (DFT + DMFT), this study shows that positron annihilation technique can provide insights into the origin of certain features of the Fermi surface topology. The experimental data obtained is in better agreement with DFT + DMFT than DFT, particularly regarding the flat bands and the van Hove singularity.
ELECTRONIC STRUCTURE
(2022)
Article
Optics
Robert Thomas, Haoyang Li, Jude Laverock, Krishna C. Balram
Summary: Understanding and mitigating optical loss is crucial for high-performance photonic integrated circuits. This study focuses on the surface absorption and scattering, which can be significant loss mechanisms in compound semiconductor (III-V) PICs. The researchers quantified the optical propagation loss in a suspended GaAs PIC platform, identified its origins through x-ray photoemission spectroscopy and spectroscopic ellipsometry, and demonstrated that surface passivation with alumina (Al2O3) can mitigate this loss.
Article
Materials Science, Multidisciplinary
L. M. Harding, E. Lawrence Bright, J. Laverock, D. T. Goddard, R. Springell
Summary: Epitaxial single crystal thin films of U3Si, U3Si5, alpha - USi2, and USi3 and polycrystalline U3Si5 were successfully synthesized using DC magnetron sputtering. These samples provide a basis for fundamental studies on the fuel candidates U3Si, U3Si5, and U3Si5 for advanced technology fuel (ATF). X-ray diffraction (XRD) and x-ray photoelectron spectroscopy (XPS) analysis show that the epitaxial phases have [001]-oriented surfaces, except for hexagonal U3Si5 which has a [100]-orientation. XPS analysis also confirms that all phases are stoichiometric within error.
Article
Chemistry, Physical
A. D. N. James, D. Billington, S. B. Dugdale
Summary: Delafossite PdCrO2 is a material that exhibits nearly-free electron and Mott insulating behavior in different layers. ARPES and Compton scattering measurements have confirmed the presence of a hexagonal Fermi surface in the material's paramagnetic phase. However, the interpretation of the Compton data, which initially suggested an additional Fermi surface feature, is being revisited. The DFT+DMFT method accurately predicts the Mott insulating state and a hexagonal Fermi surface, but fails to explain the intensity of the additional spectral weight feature observed in the Compton data. This discrepancy suggests the need for a theoretical description beyond the DFT+DMFT model to incorporate inter-layer electron coupling interactions and other vital electron interactions.
ELECTRONIC STRUCTURE
(2023)
Article
Chemistry, Physical
Matthew C. Naylor, Devendra Tiwari, Alice Sheppard, Jude Laverock, Stephen Campbell, Bethan Ford, Xinya Xu, Michael D. K. Jones, Yongtao Qu, Pietro Maiello, Vincent Barrioz, Neil S. Beattie, Neil A. Fox, David J. Fermin, Guillaume Zoppi
Summary: Cu2ZnSn(S,Se)(4) (CZTSSe) is a promising material for thin-film photovoltaics, but the open-circuit voltage deficit limits its device performance. Mitigation of defects and improvement in crystallization can be achieved through non-stoichiometric conditions and doping/alloying. In this study, Cu2ZnSnS4 nanocrystals were synthesized with a predetermined composition and doped with germanium during selenisation to aid recrystallization and reduce the effects of tin species. This resulted in structural changes, increased crystallinity and grain morphology, and improved V-OC and conversion efficiency.
FARADAY DISCUSSIONS
(2022)
Article
Physics, Multidisciplinary
A. D. N. James, M. Aichhorn, J. Laverock
Summary: The metal-insulator transition of strongly correlated 3d electrons due to quantum confinement has been investigated using the combination of dynamical mean-field theory (DMFT) and density functional theory (DFT + DMFT). The study sheds light on the microscopic mechanism of the transition and anomalous subband mass enhancement, both attributed to the quantization of V xz(yz) states in SrVO3 layers. It is shown that quantum confinement can sensitively tune the strength of electron correlations, offering potential applications in other correlated materials.
PHYSICAL REVIEW RESEARCH
(2021)
Article
Materials Science, Multidisciplinary
Michael Sekania, Andreas Ostlin, Wilhelm H. Appelt, S. B. Dugdale, Liviu Chioncel
Summary: By using a combination of density functional theory and dynamical mean-field theory, the study demonstrates that relativistic corrections in palladium lead to the formation of small hole pockets at L-symmetry points. The computed two-dimensional angular correlation of electron positron annihilation radiation (2D-ACAR) serves as clear evidence for the existence of these L-hole pockets on the Fermi surface of palladium, which are robust against electronic correlations.
Article
Materials Science, Multidisciplinary
Josef Ketels, David Billington, Stephen B. Dugdale, Michael Leitner, Christoph P. Hugenschmidt
Summary: The study utilizes two-dimensional angular correlation and Compton scattering techniques to investigate the electron momentum density and occupancy in a Pd single crystal, highlighting the complementary nature of the methods but also revealing significant discrepancies between experimental data and theoretical calculations.
Article
Materials Science, Multidisciplinary
E. Harris-Lee, A. D. N. James, S. B. Dugdale
Summary: The Fermi surface characteristics of group V and VI transition metals are sensitive to the exchange-correlation approximation, with LDA and GGA calculations inadequately capturing this feature. Among the tested exchange-correlation approximations, SCAN provides the most accurate Fermi surface predictions for these metals, but discrepancies remain in certain measurable properties, especially concerning magnetism.
Article
Materials Science, Multidisciplinary
A. D. N. James, M. Sekania, S. B. Dugdale, L. Chioncel
Summary: In this study, the magnetic Compton profiles (MCPs) of Ni were calculated using density functional theory and dynamical mean-field theory, with comparisons made between theoretical and experimental results. The total magnetic moment decreases with increasing intra-atomic Coulomb repulsion U, which is reflected in the MCPs. Experimental measurements of the total magnetic moment can be reproduced by intermediate values of U.
Article
Materials Science, Multidisciplinary
A. D. N. James, E. Harris-Lee, A. Hampel, M. Aichhorn, S. B. Dugdale
Summary: The methodology of calculating DFT wave functions with DMFT and the visualization of chemical bonds using the electron localization function (ELF) in SrVO3 and CaFe2As2 monolayers are presented. The sensitivity of ELFs to different charge redistribution scenarios in DFT calculations and the weak impact on ELFs by correlation-induced charge redistribution in CaFe2As2 phases are demonstrated. The robustness of the interlayer As-As bond in the collapsed tetragonal structure of CaFe2As2 is also highlighted.
Article
Materials Science, Multidisciplinary
D. Billington, A. D. N. James, E. Harris-Lee, D. A. Lagos, D. O'Neill, N. Tsuda, K. Toyoki, Y. Kotani, T. Nakamura, H. Bei, S. Mu, G. D. Samolyuk, G. M. Stocks, J. A. Duffy, J. W. Taylor, S. R. Giblin, S. B. Dugdale
