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An effective Hamiltonian is derived in the case of the strong Hund coupling and on-site Coulomb interaction by means of a projective perturbation approach. A physical mechanism for charge ordering in half-doped manganites…

Strongly Correlated Electrons · Physics 2009-10-31 Shun-Qing Shen , Z. D. Wang

By utilizing a multi-orbital periodic Anderson model with parameters obtained from \textit{ab initio} band structure calculations, combined with degenerate perturbation theory, we derive effective Kondo-Heisenberg and spin Hamiltonians that…

We present a systematic derivation of effective lattice spin Hamiltonians derived from a rotationally invariant multi-orbital Hubbard model including a term ensuring Hund's rule coupling. The Hamiltonians are derived down-folding the…

Mesoscale and Nanoscale Physics · Physics 2020-01-29 Markus Hoffmann , Stefan Blügel

We theoretically study a spin Hamiltonian for spin-orbit-coupled ferromagnets on the honeycomb lattice. We find that the effective Hamiltonian for magnons, a quanta of spin-wave excitations from ordered states, is equivalent to the Haldane…

Mesoscale and Nanoscale Physics · Physics 2016-11-28 Se Kwon Kim , Héctor Ochoa , Ricardo Zarzuela , Yaroslav Tserkovnyak

Hamiltonian mechanics is an effective tool to represent many physical processes with concise yet well-generalized mathematical expressions. A well-modeled Hamiltonian makes it easy for researchers to analyze and forecast many related…

Machine Learning · Computer Science 2021-02-24 Seungjun Lee , Haesang Yang , Woojae Seong

We develop a computational method to learn a molecular Hamiltonian matrix from matrix-valued time series of the electron density. As we demonstrate for three small molecules, the resulting Hamiltonians can be used for electron density…

Computational Physics · Physics 2020-09-01 Harish S. Bhat , Karnamohit Ranka , Christine M. Isborn

The change in electrical resistance associated with the application of an external magnetic field is known as the magnetoresistance (MR). The measured MR is quite complex in the class of connected networks of single-domain ferromagnetic…

We develop a machine learning method to construct accurate ground-state wave functions of strongly interacting and entangled quantum spin as well as fermionic models on lattices. A restricted Boltzmann machine algorithm in the form of an…

Strongly Correlated Electrons · Physics 2017-11-30 Yusuke Nomura , Andrew S. Darmawan , Youhei Yamaji , Masatoshi Imada

We investigate the role of exchange bridges in molecular magnets. We explore their effects on the distribution of the valence electrons and their contribution to the exchange processes. The present study is focused on a spin-half dimer with…

Atomic and Molecular Clusters · Physics 2020-10-12 M. Georgiev , H. Chamati

The application of twist engineering in van der Waals magnets has opened new frontiers in the field of two-dimensional magnetism, yielding distinctive magnetic domain structures. Despite the introduction of numerous theoretical methods,…

Strongly Correlated Electrons · Physics 2024-06-21 Woo Seok Lee , Taegeun Song , Kyoung-Min Kim

The H\"uckel Hamiltonian is an incredibly simple tight-binding model famed for its ability to capture qualitative physics phenomena arising from electron interactions in molecules and materials. Part of its simplicity arises from using only…

The recent increase in computational resources and data availability has led to a significant rise in the use of Machine Learning (ML) techniques for data analysis in physics. However, the application of ML methods to solve differential…

High Energy Physics - Theory · Physics 2025-07-18 Andrea Cipriani , Alessandro De Santis , Giorgio Di Russo , Alfredo Grillo , Luca Tabarroni

Atomistic machine learning (ML) is a powerful tool for accurate and efficient investigation of material behavior at the atomic scale. While such models have been constructed within Cartesian space to harness geometric information and…

Materials Science · Physics 2026-04-29 Qun Chen , A. S. L. Subrahmanyam Pattamatta , Boyu Wang , David J. Srolovitz , Mingjian Wen

Efficiently characterising quantum systems, verifying operations of quantum devices and validating underpinning physical models, are central challenges for the development of quantum technologies and for our continued understanding of…

Transport of quantum information in linear spin chains has been the subject of much theoretical work. Experimental studies by nuclear spin systems in solid-state by NMR (a natural implementation of such models) is complicated since the…

Quantum Physics · Physics 2009-11-13 Paola Cappellaro , Chandrasekhar Ramanathan , David G. Cory

Atomistic modelling of magnetic materials provides unprecedented detail about the underlying physical processes that govern their macroscopic properties, and allows the simulation of complex effects such as surface anisotropy, ultrafast…

We investigate the problem of determining the Hamiltonian of a locally interacting open-quantum system. To do so, we construct model estimators based on inverting a set of stationary, or dynamical, Heisenberg-Langevin equations of motion…

Quantum Physics · Physics 2020-08-19 Eugene F. Dumitrescu , Pavel Lougovski

Restricted Boltzmann machines are used for probabilistic learning and are capable of capturing complex dependencies in data. They are employed for diverse purposes such as dimensionality reduction, feature learning and can be used for…

Mesoscale and Nanoscale Physics · Physics 2024-12-10 Rehana Begum Popy , Mahdis Hamdi , Robert L. Stamps

We review the recent development of machine-learning (ML) force-field frameworks for Landau-Lifshitz-Gilbert (LLG) dynamics simulations of itinerant electron magnets, focusing on the general theory and implementations of symmetry-invariant…

Strongly Correlated Electrons · Physics 2025-01-13 Sheng Zhang , Yunhao Fan , Kotaro Shimizu , Gia-Wei Chern

We introduce a translational and rotational invariant local representation for vector fields, which can be employed in the construction of machine-learning energy models of solids and molecules. This allows us to describe, on the same…

Materials Science · Physics 2022-08-09 Michelangelo Domina , Matteo Cobelli , Stefano Sanvito