Global optimization of crystal compositions is a significant yet computationally intensive method to identify stable structures within chemical space.The specific physical properties linked to a threedimensional atomi...Global optimization of crystal compositions is a significant yet computationally intensive method to identify stable structures within chemical space.The specific physical properties linked to a threedimensional atomic arrangement make this an essential task in the development of new materials.We present a method that efficiently uses active learning of neural network force fields for structure relaxation,minimizing the required number of steps in the process.This is achieved by neural network force fields equipped with uncertainty estimation,which iteratively guide a pool of randomly generated candidates toward their respective local minima.Using this approach,we are able to effectively identify themost promising candidates for further evaluation using density functional theory(DFT).Our method not only reliably reduces computational costs by up to two orders of magnitude across the benchmark systemsSi_(16),Na_(8)Cl_(8),Ga_(8)As_(8)and Al_(4)O_(6)but also excels in finding themost stable minimum for the unseen,more complex systems Si46 and Al16O24.Moreover,we demonstrate at the example of Si_(16)that our method can find multiple relevant local minima while only adding minor computational effort.展开更多
The interplay of magnetic and semiconducting properties has been in the focus for more than a half of the century. In this introductory article we briefly review the key properties and functionalities of various magne...The interplay of magnetic and semiconducting properties has been in the focus for more than a half of the century. In this introductory article we briefly review the key properties and functionalities of various magnetic semiconductor families, including europium chalcogenides, chromium spinels, dilute magnetic semiconductors, dilute ferromagnetic semiconductors and insulators, mentioning also sources of non-uniformities in the magnetization distribution, accounting for an apparent high Curie temperature ferromagnetism in many systems. Our survey is carried out from today's perspective of ferromagnetic and antiferromagnetic spintronics as well as of the emerging fields of magnetic topological materials and atomically thin 2D layers.展开更多
We review ferromagnetic resonance(FMR)and related phenomena in the ferromagnetic semiconductor(Ga,Mn)As and single crystalline Fe/GaAs(001)hybrid structures.In both systems,spin-orbit interaction is the key ingredient...We review ferromagnetic resonance(FMR)and related phenomena in the ferromagnetic semiconductor(Ga,Mn)As and single crystalline Fe/GaAs(001)hybrid structures.In both systems,spin-orbit interaction is the key ingredient for various intriguing phenomena.展开更多
One of important challenges in condensed-matter physics is to realize new quantum states of matter by manipulating the dimensionality of materials,as represented by the discovery of high-temperature superconductivity ...One of important challenges in condensed-matter physics is to realize new quantum states of matter by manipulating the dimensionality of materials,as represented by the discovery of high-temperature superconductivity in atomic-layer pnictides and room-temperature quantum Hall effect in graphene.Tran sition-metal dichalcogenides(TMDs)provide a fertile platform for exploring novel quantum phenomena accompanied by the dimensionality change,since they exhibit a variety of electronic/magnetic states owing to quantum confinement.Here we report an anomalous metal-i nsulator transition in duced by three-dimensional(3D)-two-dimensional(2D)crossover in mono layer 1T-VSe2 grown on bilayer graphene.We observed a complete insulating state with a finite energy gap on the entire Fermi surface in monolayer 1T-VSe2 at low temperatures,in sharp contrast to metallic nature of bulk.More surprisingly,monolayer 1T-VSe2 exhibits a pseudogap with Fermi arc at temperatures above the charge-density-wave temperature,showing a close resemblanee to high-temperature cuprates.This similarity suggests a common underlying physics between two apparently different systems,pointing to the importance of charge/spin fluctuations to create the novel electronic states,such as pseudogap and Fermi arc,in these materials.展开更多
基金N.W.A.G.and M.G.contributed to this research while working at the BASLEARN-TU Berlin/BASF Joint Lab for Machine Learning,co-financed by TU Berlin and BASF SE.K.T.S.contributed to this research while working at TU Berlin and BIFOLD with grant number 01IS18037Asupported by JSPS KAKENHI Grant Number JP23H05457 and by JST-CREST Grant Number JPMJCR22O2.We thank Jonas Lederer and Klaus-Robert Müller for insightful discussions and feedback.
文摘Global optimization of crystal compositions is a significant yet computationally intensive method to identify stable structures within chemical space.The specific physical properties linked to a threedimensional atomic arrangement make this an essential task in the development of new materials.We present a method that efficiently uses active learning of neural network force fields for structure relaxation,minimizing the required number of steps in the process.This is achieved by neural network force fields equipped with uncertainty estimation,which iteratively guide a pool of randomly generated candidates toward their respective local minima.Using this approach,we are able to effectively identify themost promising candidates for further evaluation using density functional theory(DFT).Our method not only reliably reduces computational costs by up to two orders of magnitude across the benchmark systemsSi_(16),Na_(8)Cl_(8),Ga_(8)As_(8)and Al_(4)O_(6)but also excels in finding themost stable minimum for the unseen,more complex systems Si46 and Al16O24.Moreover,we demonstrate at the example of Si_(16)that our method can find multiple relevant local minima while only adding minor computational effort.
基金supported by the Foundation for Polish Science through the IRA Programme financed by EU within SG OP Programmesupport by the Austrian Science Foundation-FWF (P31423 and P26830)the Austrian Exchange Service (OAD) Project PL-01/2017
文摘The interplay of magnetic and semiconducting properties has been in the focus for more than a half of the century. In this introductory article we briefly review the key properties and functionalities of various magnetic semiconductor families, including europium chalcogenides, chromium spinels, dilute magnetic semiconductors, dilute ferromagnetic semiconductors and insulators, mentioning also sources of non-uniformities in the magnetization distribution, accounting for an apparent high Curie temperature ferromagnetism in many systems. Our survey is carried out from today's perspective of ferromagnetic and antiferromagnetic spintronics as well as of the emerging fields of magnetic topological materials and atomically thin 2D layers.
基金The work at Tohoku University was partially supported by Grant-in-Aids from MEXT and JSPS.
文摘We review ferromagnetic resonance(FMR)and related phenomena in the ferromagnetic semiconductor(Ga,Mn)As and single crystalline Fe/GaAs(001)hybrid structures.In both systems,spin-orbit interaction is the key ingredient for various intriguing phenomena.
文摘One of important challenges in condensed-matter physics is to realize new quantum states of matter by manipulating the dimensionality of materials,as represented by the discovery of high-temperature superconductivity in atomic-layer pnictides and room-temperature quantum Hall effect in graphene.Tran sition-metal dichalcogenides(TMDs)provide a fertile platform for exploring novel quantum phenomena accompanied by the dimensionality change,since they exhibit a variety of electronic/magnetic states owing to quantum confinement.Here we report an anomalous metal-i nsulator transition in duced by three-dimensional(3D)-two-dimensional(2D)crossover in mono layer 1T-VSe2 grown on bilayer graphene.We observed a complete insulating state with a finite energy gap on the entire Fermi surface in monolayer 1T-VSe2 at low temperatures,in sharp contrast to metallic nature of bulk.More surprisingly,monolayer 1T-VSe2 exhibits a pseudogap with Fermi arc at temperatures above the charge-density-wave temperature,showing a close resemblanee to high-temperature cuprates.This similarity suggests a common underlying physics between two apparently different systems,pointing to the importance of charge/spin fluctuations to create the novel electronic states,such as pseudogap and Fermi arc,in these materials.
