Article
Optics
Raul Bombin, Viktor Cikojevic, Juan Sanchez-Baena, Jordi Boronat
Summary: This study focuses on the repulsive Fermi polaron in a two-component, two-dimensional system of fermionic atoms, investigating properties such as polaron energy, quasiparticle residue, and effective mass using the diffusion Monte Carlo method. The results highlight the importance of considering the effective range and scattering length to reproduce experimental results, as well as the establishment of universality through different model potentials for the interaction between the Fermi sea and the impurity. This underscores the significance of quantum fluctuations and beyond mean-field effects in accurately describing the Fermi polaron problem.
Article
Physics, Multidisciplinary
Ivan P. Christov
Summary: The time-dependent quantum Monte Carlo method is used to calculate the entanglement of electrons in one-dimensional quantum dots with various spin configurations. The study finds that the spatial entanglement differs in parallel-spin and spin-compensated cases, with outermost opposite-spin electrons behaving like bosons in the latter case. The results are consistent with numerically exact results where comparison is possible.
Article
Chemistry, Physical
Juha Tiihonen, Paul R. C. Kent, Jaron T. Krogel
Summary: This paper presents an energy-based method for efficient structural optimization with stochastic electronic structure theories. The method utilizes robust line-search energy minimization in reduced parameter space and surrogate theory to maximize statistical efficiency and retain controllable accuracy. The authors demonstrate the effectiveness and wide applicability of the method by finding the minimum DMC energy structures of selected aromatic molecules.
JOURNAL OF CHEMICAL PHYSICS
(2022)
Article
Multidisciplinary Sciences
Wilson Tsakane Mongwe, Rendani Mbuvha, Tshilidzi Marwala
Summary: Hamiltonian Monte Carlo (HMC) is a popular algorithm in machine learning that generates distant proposals using Hamiltonian dynamics. An extension to HMC, Magnetic Hamiltonian Monte Carlo (MHMC), adds a magnetic field to introduce non-canonical dynamics. The Quantum-Inspired Magnetic Hamiltonian Monte Carlo (QIMHMC) algorithm combines non-canonical dynamics of MHMC with random mass matrix, showing better sampling performance than HMC and MHMC.
Article
Physics, Multidisciplinary
Minghui Hu, Youjin Deng, Jian-Ping Lv
Summary: The concept of logarithmic universality presents a new model for describing critical phenomena, characterized by distinct features from the standard scenario. Monte Carlo simulations on the three-dimensional XY model provide strong evidence for the emergence of logarithmic universality. Discussions on finite-size scaling and critical exponent offer a new perspective on understanding critical universality.
PHYSICAL REVIEW LETTERS
(2021)
Article
Chemistry, Physical
Oliver A. Bramley, Timothy J. H. Hele, Dmitrii Shalashilin
Summary: Zombie states are a formalism that describes coupled coherent fermionic states in a computationally tractable manner. This study extends the previous work on Zombie states and develops efficient algorithms for evaluating operators and addressing normalization. It also presents techniques for improving accuracy and calculating low-lying excited states.
JOURNAL OF CHEMICAL PHYSICS
(2022)
Article
Materials Science, Multidisciplinary
Matteo Barborini, Matteo Calandra, Francesco Mauri, Ludger Wirtz, Pierluigi Cudazzo
Summary: This work investigates the purely electronic instability in one-dimensional semimetals independent of a lattice distortion by accurate ab initio calculations on one-dimensional carbon chain and monatomic hydrogen chain based on quantum Monte Carlo and hybrid density functional theory.
Article
Chemistry, Physical
Jonas Feldt, Antoine Bienvenu, Roland Assaraf
Summary: In this paper, a new estimator in the variational Monte Carlo framework is proposed, which utilizes numerically cheap single-core subsamplings to improve the estimation of molecular properties. Furthermore, a spin-dependent core definition is introduced to simplify the algorithm and enhance its efficiency.
PHYSICAL CHEMISTRY CHEMICAL PHYSICS
(2022)
Article
Chemistry, Physical
Giovani L. Rech, Andre L. Martinotto, Janete E. Zorzi, Claudio A. Perottoni
Summary: The relative stability between the crystal structure of alpha-F-2, space group C2/c, and a hypothesized high-pressure phase, space group Cmce, was investigated using Density Functional Theory and Quantum Monte Carlo calculations. The analysis of the phonon dispersion spectra showed that the Cmce phase exhibits dynamical instability near the Gamma-point at ambient pressure, which disappears under increasing pressure. This instability is attributed to the absence of sigma-holes in the fluorine molecule, resulting in repulsive head-to-head interactions between molecules.
PHYSICAL CHEMISTRY CHEMICAL PHYSICS
(2023)
Article
Materials Science, Multidisciplinary
Yuichi Motoyama, Kazuyoshi Yoshimi, Junya Otsuki
Summary: Analytic continuation from the imaginary-time Green's function to the spectral function is crucial for studying the dynamical properties of quantum many-body systems. However, this process is unstable and has advantages and disadvantages. Combining SpM AC with Pade approximation in the SpM-Pade method can provide more accurate and stable results.
Article
Physics, Multidisciplinary
Indrajit Sau, Arnab Sen, Debasish Banerjee
Summary: Matter-free lattice gauge theories provide an ideal model for studying the confinement to deconfinement transitions at finite temperatures, and the critical exponents can change continuously with varying coupling while maintaining a fixed ratio. This phenomenon, known as weak universality, has been demonstrated for the first time in lattice gauge theories. Using an efficient cluster algorithm, we show that the finite temperature phase transition of U(1) quantum link lattice gauge theory belongs to the 2D XY universality class, and the occurrence of weak universality is observed when higher charged matter fields are added.
PHYSICAL REVIEW LETTERS
(2023)
Article
Materials Science, Multidisciplinary
Fu-Jiun Jiang
Summary: In this study, the numerical value of χ(u)c(2)/T, a universal quantity associated with the quantum critical regime, is calculated for a two-dimensional dimerized spin-1/2 antiferromagnet using quantum Monte Carlo simulations. By simulating large lattices at moderately low temperatures, it is found that χ(u)c(2)/T is approximately 0.32. The estimation deviates from the related analytic prediction but agrees with recent numerical calculations of other 2D dimerized spin-1/2 antiferromagnets.
RESULTS IN PHYSICS
(2023)
Article
Chemistry, Physical
Tina N. Mihm, William Z. Van Benschoten, James J. Shepherd
Summary: A new approach using low-cost calculations was developed to find a twist angle that matches the coupled cluster doubles energy in a finite unit cell. The method was shown to have comparable accuracy with exact methods beyond coupled cluster doubles theory. Additionally, for small system sizes, the same twist angle can be found by comparing energies directly, suggesting a potential route towards twist angle selection.
JOURNAL OF CHEMICAL PHYSICS
(2021)
Article
Multidisciplinary Sciences
Yan-Cheng Wang, Meng Cheng, William Witczak-Krempa, Zi Yang Meng
Summary: The experimental discovery of Anyons in two-dimensional electron gases has opened up new possibilities for studying quantum particles beyond bosons and fermions. Large-scale quantum Monte Carlo simulations have revealed unique conductivity properties near a phase transition, with implications for quantum materials research.
NATURE COMMUNICATIONS
(2021)
Article
Multidisciplinary Sciences
Jan Kessler, Francesco Calcavecchia, Thomas D. Kuehne
Summary: Inspired by the universal approximation theorem and the widespread adoption of artificial neural network techniques, feed-forward neural networks are proposed as a general purpose trial wave function for quantum Monte Carlo simulations of continuous many-body systems. The accuracy of the trial wave functions was demonstrated by studying an exactly solvable model system of two trapped interacting particles and the hydrogen dimer. The whole many-body wave function can be represented by a neural network for simple model systems, while the antisymmetry condition of non-trivial fermionic systems is incorporated by means of a Slater determinant.
ADVANCED THEORY AND SIMULATIONS
(2021)
Article
Chemistry, Physical
Juha Tiihonen, Paul R. C. Kent, Jaron T. Krogel
Summary: This paper presents an energy-based method for efficient structural optimization with stochastic electronic structure theories. The method utilizes robust line-search energy minimization in reduced parameter space and surrogate theory to maximize statistical efficiency and retain controllable accuracy. The authors demonstrate the effectiveness and wide applicability of the method by finding the minimum DMC energy structures of selected aromatic molecules.
JOURNAL OF CHEMICAL PHYSICS
(2022)
Article
Chemistry, Physical
Daniel Staros, Guoxiang Hu, Juha Tiihonen, Ravindra Nanguneri, Jaron Krogel, M. Chandler Bennett, Olle Heinonen, Panchapakesan Ganesh, Brenda Rubenstein
Summary: In this study, the structural, electronic, and magnetic properties of monolayer CrI3 are predicted using Density Functional Theory (DFT) and high-accuracy Diffusion Monte Carlo (DMC) simulations. The results show that DFT predictions of magnetic spin moments in monolayer CrI3 are on average correct but miss critical local spatial fluctuations in the spin density revealed by the more accurate DMC. Moreover, substantial spin-phonon coupling is observed in monolayer CrI3.
JOURNAL OF CHEMICAL PHYSICS
(2022)
Article
Chemistry, Physical
Daniel Wines, Kayahan Saritas, Can Ataca
Summary: In this study, different electronic structure methods were used to calculate the magnetic properties of monolayer MnO2. It was found that ferromagnetic ordering is more favorable than antiferromagnetic ordering, and a statistical bound on the magnetic exchange parameter was determined. Using an analytical model, an upper bound for the critical temperature of MnO2 was estimated, providing an accurate theoretical benchmark for the realization and development of future 2D magnetic devices.
JOURNAL OF PHYSICAL CHEMISTRY C
(2022)
Article
Chemistry, Physical
Daniel Wines, Kamal Choudhary, Francesca Tavazza
Summary: This study designed a workflow that combines DFT+U and DMC to treat correlated magnetic systems in 2D materials. By applying this workflow, the analysis of CrI3 and CrBr3 revealed their critical temperatures to be 43.56 K and 20.78 K respectively, along with the examination of spin densities and magnetic properties using DMC and DFT+U. It is expected that this workflow will play a significant role in the future discovery and characterization of complex correlated 2D magnetic materials.
JOURNAL OF PHYSICAL CHEMISTRY C
(2023)
Article
Chemistry, Multidisciplinary
Daniel Wines, Kamal Choudhary, Adam J. Biacchi, Kevin F. Garrity, Francesca Tavazza
Summary: High-throughput DFT calculations were employed to systematically search for conventional superconductors, including two-dimensional (2D) materials. Over 1000 2D materials in the JARVIS-DFT database were screened, and electron-phonon coupling calculations were performed to determine the superconducting transition temperature (Tc) for 165 materials. Among them, 34 dynamically stable structures with Tc above 5 K were identified, including previously unreported Mg2B4N2 (Tc = 21.8 K). Experimental measurements of selected layered superconductors were also conducted and discussed within the context of DFT results. The workflow outcomes provide a roadmap for future computational and experimental studies of new and emerging 2D superconductors.
Article
Chemistry, Physical
Juha Tiihonen, Hannu Hakkinen
Summary: We study the potential use of quantum Monte Carlo techniques to optimize the electronic wavefunctions and atomic geometries of gold compounds. We show that these methods can mitigate the limitations of density functional theory and achieve more accurate and consistent results for gold nanoclusters. In addition, we demonstrate a robust and scalable optimization workflow for thiolated gold clusters with 1-3 gold atoms.
JOURNAL OF CHEMICAL PHYSICS
(2023)
Article
Chemistry, Physical
Daniel Wines, Tian Xie, Kamal Choudhary
Summary: This study presents a diffusion model inspired by computer vision community to generate new superconductors with unique structures and chemical compositions. By using crystaldiffusion variational autoencoder (CDVAE) and atomistic line graph neural network (ALIGNN) models, along with superconducting database of density functional theory (DFT) calculations, new superconductors with a high success rate have been generated.
JOURNAL OF PHYSICAL CHEMISTRY LETTERS
(2023)
Article
Materials Science, Multidisciplinary
Guillaume Marcaud, Alex Taekyung Lee, Adam J. Hauser, F. Y. Yang, Sangjae Lee, Diego Casa, Mary Upton, Thomas Gog, Kayahan Saritas, Yilin Wang, Mark P. M. Dean, Hua Zhou, Zhan Zhang, Ignace Jarrige, Sohrab Ismail-Beigi, Charles Ahn
Summary: This study reveals the low-energy landscape and underlying mechanisms of the ferrimagnetic Sr2CrReO6 double perovskite, highlighting the competition between spin-orbit coupling, Hund's coupling, and strain-induced crystal field. Experimental and computational methods are employed to investigate the nature of excitations and the presence of orbital ordering in this material.
Article
Materials Science, Multidisciplinary
Kayahan Saritas, Sohrab Ismail-Beigi
Summary: We predict that monolayer FeCl2 is a two-dimensional piezoelectric ferromagnet with easy-axis magnetism and a Curie temperature of 260 K. Our ab initio calculations combined with data mining reveal 2H-FeCl2 as the only easy-axis 2D monolayer piezoelectric ferromagnet, and show that its magnetic anisotropy increases significantly with moderate hole doping. We develop an analysis based on magnetic anisotropies densities that explain the magnetic and doping-dependent behavior of FeCl2, as well as VSe2 and CrI3, and can guide the design of future 2D magnetically ordered materials.
Article
Materials Science, Multidisciplinary
Nassar Doudin, Kayahan Saritas, Min Li, Inga Ennen, J. Anibal Boscoboinik, Petr Dementyev, Andreas Hutten, Sohrab Ismail-Beigi, Eric I. Altman
Summary: The intrinsic properties of two-dimensional SiO2 were revealed by forming the material on inert Au(111). The formation of a crystalline phase consisting of tetrahedral [SiO4] building units was enabled by SiO deposition. The twisting and rippling of the 2D kagome lattice provide 2D silica with the flexibility to adapt to strain and changes in the crystallographic direction without introducing defects.
ACS MATERIALS LETTERS
(2022)
Article
Optics
Alpi Tolvanen, Juha Tiihonen, Tapio T. Rantala
Summary: This paper investigates the effects of finite temperature and finite nuclear masses on the diamagnetism of small atoms and molecules. A nonrelativistic path-integral Monte Carlo simulation is used to sample the exact Coulomb pair density matrices of electrons and nuclei at finite temperatures. The results are consistent with previous studies and demonstrate additional thermal effects on the diamagnetic response of low-mass systems.
