Article
Computer Science, Interdisciplinary Applications
P. Arthuis, A. Tichai, J. Ripoche, T. Duguet
Summary: The second version of the code ADG automates the generation and evaluation of valid off-diagonal Bogoliubov many-body perturbation theory diagrams. It can handle Hamiltonians with both two-body and three-body interactions, and utilizes algebraic Feynman's rules and diagrammatic rules for evaluation. The program has been optimized for efficiency and moved to Python3, while still supporting Python2.
COMPUTER PHYSICS COMMUNICATIONS
(2021)
Article
Materials Science, Multidisciplinary
Evan Sheridan, Christopher Rhodes, Francois Jamet, Ivan Rungger, Cedric Weber
Summary: Machine learning provides new possibilities for modeling correlated materials, but quantum embedding methods like dynamical mean-field theory face limitations on classical computing architectures. A data-driven machine learning process has been outlined for solving the Anderson impurity model, improving the accuracy and speed of solutions. This approach, known as data-driven dynamical mean-field theory (d3MFT), advances the field by enabling faster and more accurate calculations of strongly correlated materials.
Article
Physics, Multidisciplinary
P. Demol, M. Frosini, A. Tichai, V. Soma, T. Duguet
Summary: A novel many-body method called Bogoliubov many-body perturbation theory (BMBPT) has been developed to accurately and efficiently solve the A-body Schrödinger equation for open-shell nuclei. The perturbation theory must operate under the constraint that the average number of particles is self-consistently adjusted at each perturbative order, and it has been shown that using a resummation method like eigenvector continuation can improve accuracy and convergence towards CI results.
Article
Chemistry, Multidisciplinary
Fabien Bruneval, Nike Dattani, Michiel J. van Setten
Summary: This study systematically evaluates the quality of several perturbation theories against high-level quantum chemistry methods, finding GW to be the most accurate approximation for ionization potentials. Attempts to improve upon GW by adding more diagrams were mostly unsuccessful, with only the inclusion of a GW density-matrix showing positive impact. Additionally, using an improved hybrid functional for the non-interacting Green's function further enhanced the accuracy of the simplest GW approximation.
FRONTIERS IN CHEMISTRY
(2021)
Article
Chemistry, Physical
Juan J. J. Aucar, Alejandro F. F. Maldonado, Juan I. I. Melo
Summary: In this work, relativistic corrections to the electric field gradient (EFG) are presented, including spin-dependent corrections for the first time. The results show that these new corrections significantly improve the performance of the existing method and are in close agreement with calculations at the four-component Dirac-Hartree-Fock (4c-DHF) level. The accuracy of the EFG values obtained with this new method allows for the analysis of the electronic origin of relativistic effects using well-known nonrelativistic operators.
JOURNAL OF CHEMICAL PHYSICS
(2022)
Review
Physics, Multidisciplinary
Karsten Held, Liang Si, Paul Worm, Oleg Janson, Ryotaro Arita, Zhicheng Zhong, Jan M. Tomczak, Motoharu Kitatani
Summary: In this study, the electronic structure of nickelate superconductors is reviewed, with and without considering the effects of electronic correlations. The results reveal that specific orbitals and an electron reservoir play key roles in the superconducting doping regime. Furthermore, the study finds that different physical phenomena can emerge under specific conditions, suggesting that different mechanisms may affect the occurrence of superconductivity.
FRONTIERS IN PHYSICS
(2022)
Review
Chemistry, Multidisciplinary
Justus A. Calvin, Chong Peng, Varun Rishi, Ashutosh Kumar, Edward F. Valeev
Summary: This review examines the deployment of many-body quantum chemistry methods on high-performance computing platforms, specifically focusing on accurate methods like the coupled-cluster method. Before discussing relevant literature, it analyzes the current and future HPC landscape and the computational characteristics of many-body methods that pose challenges to their implementation on HPC systems.
Article
Physics, Nuclear
Theodore Depastas, George A. Souliotis, Demeter Tzeli, Sotiris S. Xantheas
Summary: This study extends the many-body expansion (MBE) to the light nuclear systems 3H and 3He, considering the nucleonic degrees of freedom. The total energy of the 2H nucleus is calculated using the Pauli nucleonic dynamics (PND) model and is found to be in good agreement with the experimental value. The application of MBE yields results for the three-body term in the 3H nucleus comparable with previous estimates, and for the first time for the 3He nucleus.
Article
Materials Science, Multidisciplinary
Steffen Backes, Jae-Hoon Sim, Silke Biermann
Summary: Motivated by the physics of quasi-two-dimensional fermionic systems, many-body computational methods that include both local and nonlocal electronic correlations are rapidly evolving. Methods may be hindered by the emergence of noncausal features, but the presented approach extends local many-body techniques to nonlocal correlations while preserving causality.
Article
Chemistry, Physical
Jing Shang, Congxin Xia, Chun Tang, Chun Li, Yandong Ma, Yuantong Gu, Liangzhi Kou
Summary: The bending deformation of AgBiP2Se6 monolayers can manipulate the polarization direction and domain size, significantly improving the ferroelectric stability. This mechano-ferroelectric coupling represents a new mechanism for stabilization and polarization flip in 2D ferroelectrics, with potential applications in next-generation non-volatile storage devices.
NANOSCALE HORIZONS
(2021)
Article
Chemistry, Multidisciplinary
Eric R. Heller, Jeremy O. Richardson
Summary: This study simulates two recent matrix-isolation experiments at cryogenic temperatures, revealing the failure of the commonly used weak-coupling method in describing deep-tunneling reactions. However, the more rigorous approach of semiclassical golden-rule instanton theory combined with double-hybrid density-functional theory and multireference perturbation theory successfully reproduces rate constants and kinetic isotope effects in good agreement with experiment. Additionally, these calculations identify the optimal tunnelling pathways, providing a molecular picture of the reaction mechanism.
ANGEWANDTE CHEMIE-INTERNATIONAL EDITION
(2022)
Article
Chemistry, Physical
Chayan Patra, Valay Agarawal, Dipanjali Halder, Anish Chakraborty, Dibyendu Mondal, Sonaldeep Halder, Rahul Maitra
Summary: The coupled cluster iteration scheme for determining the cluster amplitudes involves nonlinearly coupled difference equations, and can be analyzed as a multivariate time-discrete map. The identification of highly damped auxiliary amplitudes allows for a decoupling of the amplitudes, reducing computational scaling without sacrificing accuracy in the ground state energy.
Article
Chemistry, Physical
Alexander Bakulin, Lora S. Chumakova, Svetlana E. Kulkova
Summary: The oxygen absorption energy and migration barriers in titanium silicide with composition Ti5Si3 and hexagonal structure have been calculated, and the diffusion mechanism of oxygen in this material has been discussed. The obtained diffusion coefficient of oxygen in Ti5Si3 is comparable to experimental values for metal oxides.
Article
Mathematics, Applied
Lin Lin, Michael Lindsey
Summary: Quantum embedding theories are powerful tools for approximately solving large-scale, strongly correlated quantum many-body problems. The variational embedding method guarantees a one-sided bound for the exact ground-state energy and can be systematically improved for increased accuracy. By relaxing representability conditions to a set of constraints, this method can be applied to both quantum spin systems and fermionic systems.
COMMUNICATIONS ON PURE AND APPLIED MATHEMATICS
(2022)
Article
Materials Science, Multidisciplinary
M. Yarmohammadi, C. Meyer, B. Fauseweh, B. Normand, G. S. Uhrig
Summary: This study investigates the dynamical properties of a gapped quantum spin system coupled to a laser electric field, driving resonant excitation of specific phonon modes modulating the magnetic interactions. By developing quantum master equations governing the time-evolution of both lattice and spin sectors, using a Lindblad formalism, the study explores nonequilibrium steady states (NESS) of the spin system and their related nontrivial properties. Focus is placed on the regime of weak spin-phonon coupling, characterizing the NESS by their frequency and wave-vector content, exploring their transient and relaxation behavior, and discussing the energy flow, system temperature, and critical role of the type of bath adopted.
Article
Computer Science, Interdisciplinary Applications
Josef Kaufmann, Karsten Held
Summary: This article presents the Python package ana_cont, which is used for the analytic continuation of fermionic and bosonic many-body Green's functions using either the Pade approximants method or the maximum entropy method. The determination of hyperparameters and the implementation are described in detail. The code is publicly available on GitHub, where documentation and learning resources are also provided.
COMPUTER PHYSICS COMMUNICATIONS
(2023)
Article
Materials Science, Multidisciplinary
A. A. Katanin, A. S. Belozerov, A. I. Lichtenstein, M. I. Katsnelson
Summary: We analyze possible ways to calculate magnetic exchange interactions within the density functional theory plus dynamical mean-field theory (DFT+DMFT) approach in the paramagnetic phase. Using the susceptibilities obtained within the ladder DMFT approach together with the random phase approximation result for the Heisenberg model, we obtain bilinear exchange interactions. We show that the earlier obtained result of Stepanov individual magnetic moments in each orbital in the leading-order approximation in the nonlocal correlations.
Article
Materials Science, Multidisciplinary
I. A. Goremykin, A. A. Katanin
Summary: We propose a dynamical mean-field theory approach for the study of spiral magnetic order, which includes impurity solvers for the diagonal local Green's function. By considering nonuniform dynamic magnetic susceptibilities in a local coordinate frame, we describe the evolution of magnetic order in the t-t' Hubbard model. We find that with doping, the antiferromagnetic order changes to an incommensurate one and then to the paramagnetic phase.
Article
Materials Science, Multidisciplinary
Patrick Kappl, Friedrich Krien, Clemens Watzenboeck, Karsten Held
Summary: By calculating the three-particle response of the Anderson impurity model, we find that genuine three-particle vertex corrections are significant and cannot be neglected by only considering bare bubble terms or corrections based on the two-particle vertex.
Article
Materials Science, Multidisciplinary
Liang Si, Paul Worm, Dachuan Chen, Karsten Held
Summary: Despite extensive experimental and theoretical efforts, understanding the magnetic and electronic properties of superconducting nickelates remains challenging due to hidden factors in the synthesized films. One possible hidden factor is the intercalation of hydrogen during the chemical reduction process. The formation of hydrogen chains in LaNiO2 superconductors may explain the observed charge order states and make synthesizing homogeneous nickelates more difficult.
Article
Materials Science, Multidisciplinary
Ruiqi Ku, Luo Yan, Jian-Guo Si, Songyuan Zhu, Bao-Tian Wang, Yadong Wei, Kaijuan Pang, Weiqi Li, Liujiang Zhou
Summary: Based on first principles, this study investigates the Janus 2H-MoSH monolayer and reports the global minimum structure of a Janus 1T-MoSH monolayer. The 2H-MoSH monolayer can easily transform into the 1T phase with a small barrier. The Janus 1T-MoSH is a charge-density wave (CDW) material whose CDW order can be regulated through external strains. Under 3% compressive strain, the CDW in Janus 1T-MoSH is suppressed and a superconducting state with a transition temperature of 25.15 K emerges. The Janus 2H-MoSH monolayer is an intrinsic superconductor with a transition temperature of 26.81 K, which can be enhanced to 36.69 K under 1% tensile strain.
Article
Materials Science, Multidisciplinary
P. A. Igoshev, A. A. Katanin
Summary: We use the functional renormalization group technique with temperature as a scale parameter to investigate the possibility of ferromagnetic ordering in the nondegenerate Hubbard model on the face-centered cubic lattice. By assuming the relations between hopping parameters, we find that ferromagnetic instability forms with decreasing temperature. We calculate the phase diagrams of chemical potential versus temperature and find that ferromagnetic order only occurs when the density of states diverges and the fillings are near the van Hove singularity. The obtained Curie temperature is significantly smaller compared to the results of the random-phase approximation.
Article
Materials Science, Multidisciplinary
A. S. Belozerov, A. A. Katanin, V. I. Anisimov
Summary: We investigate the effects of electron correlations on the magnetic properties of bcc vanadium using density functional and dynamical mean-field theory. Our calculations demonstrate that the temperature dependence of the magnetic susceptibility in the bcc structure can be qualitatively reproduced without considering the martensitic phase transition. We find that the Curie-Weiss behavior arises from the partial formation of local magnetic moments due to local spin correlations caused by Hund's rule coupling.
Article
Materials Science, Multidisciplinary
Simone Di Cataldo, Paul Worm, Liang Si, Karsten Held
Summary: A recent experiment suggests that superconductivity in nickelates is limited to a specific range of hydrogen concentration. The necessity of hydrogen indicates its crucial role in superconductivity. However, calculations using density-functional theory show that the electron-phonon coupling in hydrogen-intercalated nickelates is not strong enough to explain the observed superconductivity.
Article
Materials Science, Multidisciplinary
T. B. Mazitov, A. A. Katanin
Summary: This study investigates the impact of the formation and screening of local magnetic moments on the temperature and interaction dependencies of spectral functions and resistivity. The results indicate that, at half filling, the maximum resistivity corresponds to the appearance of a central quasiparticle peak in the spectral function and the transition to a metallic regime with well-defined fermionic quasiparticles. The temperature at which the screening of local magnetic moments occurs is lower than the temperature scale of the maximum resistivity, and at half filling, it coincides with the boundary corresponding to the exponent of resistivity.
Article
Materials Science, Multidisciplinary
Gergo Roosz, Karsten Held
Summary: We study the exact reduced density matrix for electrons in an analytically solvable electron-phonon model and derive analytical expressions for electron-phonon entanglement, spectrum, and mutual information at finite and zero temperature.
Article
Physics, Multidisciplinary
Matthias Pickem, Jan M. Tomczak, Karsten Held
Summary: The two-dimensional nature of engineered transition-metal ultrathin oxide films provides a large playground for studying yet to be fully understood physics. This study focuses on pristine SrVO3 monolayers and reveals the effects of nonlocal magnetic and orbital fluctuations on the self-energy, as well as the differentiation between momenta on the occupied and unoccupied sides of the Fermi surface.
PHYSICAL REVIEW RESEARCH
(2022)
Article
Physics, Multidisciplinary
Markus Wallerberger, Karsten Held
Summary: Ranking bit patterns is a significant bottleneck in numerical quantum many-body calculations. Traditional bisectioning search has poor cache performance, but using tries (prefix trees) can achieve a two-to tenfold speedup with moderate memory overhead. For ranking permutations, compressed tries offer considerable speedup while maintaining memory requirements.
PHYSICAL REVIEW RESEARCH
(2022)
Article
Materials Science, Multidisciplinary
C. Watzenboeck, M. Wallerberger, L. Ruzicka, P. Worm, K. Held, A. Kauch
Summary: In this study, we investigate photoexcitations in small Hubbard clusters and find that some clusters exhibit an increase in double occupation through impact ionization after an electric field pulse. By treating the electromagnetic field classically and using exact diagonalization, we are able to identify the many-body eigenstates responsible for impact ionization and observe pronounced changes in double occupation and spin energy. Our analysis shows that the increase in spin energy is not significant for impact ionization. We also demonstrate that the characteristic peak structure of the optical conductivity in one-dimensional chains is solely due to vertex corrections.
Article
Materials Science, Multidisciplinary
Motoharu Kitatani, Ryotaro Arita, Thomas Schaefer, Karsten Held
Summary: We review recent studies on superconductivity using diagrammatic extensions of dynamical mean field theory, which consider both local correlation effects and spatial long-range fluctuations. The results reproduce and predict experimental phase diagrams of strongly correlated systems, and reveal that the dynamical screening effect of the pairing interaction vertex has significant consequences for the transition temperature.
JOURNAL OF PHYSICS-MATERIALS
(2022)
