Shivendra Kumar Gupta, Ashish Kore, Saurabh Kumar Sen, Poorva Singh
Nodal line semimetals represent precursor states for various topological phases, exhibiting intrinsic topological characteristics and intriguing properties. These materials host rare and distinctive topological features, which can give rise to exotic phenomena, thereby garnering significant attention in both fundamental research and technological applications. In this study, we conduct ab-initio calculations to explore the properties of SrCaX (X = Bi, Sb, As, P), identifying these as multiple Dirac nodal line semimetals protected by Z2 quantized Berry phases and manifesting multiple drum-head-like surface states. The nodal lines in these compounds are situated at the M point when kz = 0 and at the A point when kz = {pi}. Notably, SrCaX family exhibits a unique characteristic wherein they host both type II Dirac point and topological nodal line semimetal within a single crystal structure, hence providing an excellent platform for studying the interplay between different topological properties. Additionally, in SrCaP topological Dirac semimetal, Type II Dirac point and topological nodal line semimetal features coexist in a single crystal. These special features in this series of materials make them ideal candidates for further investigation by experimental means.
对偶线半金属是各种拓扑相的前驱态，表现出固有的拓扑特性和引人入胜的性质。这些材料具有罕见而独特的拓扑特征，可以产生奇异的现象，因此在基础研究和技术应用方面都备受关注。在这项研究中，我们进行了无损计算来探索 SrCaX（X= Bi、Sb、As、P）的性质，确定它们是受 Z2 量化贝里相保护的多狄拉克结点线半金属，并表现出多个类似鼓头的表面态。当 kz = 0 时，这些化合物中的结点线位于 M 点；当 kz = {pi} 时，结点线位于 A 点。值得注意的是，SrCaX 家族表现出一种独特的特性，即它们在单晶结构中同时容纳了 II 型狄拉克点和拓扑节点线半金属，从而为研究不同拓扑性质之间的相互作用提供了一个绝佳的平台。此外，在 SrCaP 拓扑狄拉克半金属中，II 型狄拉克点和拓扑结点线半金属特性共存于单晶体中。这一系列材料的这些特殊特性使它们成为通过实验手段进行进一步研究的理想候选材料。
{"title":"Coexistence of Topological Dirac and Dirac Nodal line semimetal in SrCaP belonging to Nodal line semimetal family SrCaX(X= Bi, Sb, As, P)","authors":"Shivendra Kumar Gupta, Ashish Kore, Saurabh Kumar Sen, Poorva Singh","doi":"arxiv-2406.03952","DOIUrl":"https://doi.org/arxiv-2406.03952","url":null,"abstract":"Nodal line semimetals represent precursor states for various topological\u0000phases, exhibiting intrinsic topological characteristics and intriguing\u0000properties. These materials host rare and distinctive topological features,\u0000which can give rise to exotic phenomena, thereby garnering significant\u0000attention in both fundamental research and technological applications. In this\u0000study, we conduct ab-initio calculations to explore the properties of SrCaX (X\u0000= Bi, Sb, As, P), identifying these as multiple Dirac nodal line semimetals\u0000protected by Z2 quantized Berry phases and manifesting multiple drum-head-like\u0000surface states. The nodal lines in these compounds are situated at the M point\u0000when kz = 0 and at the A point when kz = {pi}. Notably, SrCaX family exhibits\u0000a unique characteristic wherein they host both type II Dirac point and\u0000topological nodal line semimetal within a single crystal structure, hence\u0000providing an excellent platform for studying the interplay between different\u0000topological properties. Additionally, in SrCaP topological Dirac semimetal,\u0000Type II Dirac point and topological nodal line semimetal features coexist in a\u0000single crystal. These special features in this series of materials make them\u0000ideal candidates for further investigation by experimental means.","PeriodicalId":501211,"journal":{"name":"arXiv - PHYS - Other Condensed Matter","volume":"33 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-06-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141520117","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Michael Chilcote, Alessandro R. Mazza, Qiangsheng Lu, Isaiah Gray, Qi Tian, Qinwen Deng, Duncan Moseley, An-Hsi Chen, Jason Lapano, Jason S. Gardner, Gyula Eres, T. Zac Ward, Erxi Feng, Huibo Cao, Valeria Lauter, Michael A. McGuire, Raphael Hermann, David Parker, Myung-Geun Han, Asghar Kayani, Gaurab Rimal, Liang Wu, Timothy R. Charlton, Robert G. Moore, Matthew Brahlek
The field of spintronics has seen a surge of interest in altermagnetism due to novel predictions and many possible applications. MnTe is a leading altermagnetic candidate that is of significant interest across spintronics due to its layered antiferromagnetic structure, high Neel temperature (TN ~ 310 K) and semiconducting properties. We present results on molecular beam epitaxy (MBE) grown MnTe/InP(111) films. Here, it is found that the electronic and magnetic properties are driven by the natural stoichiometry of MnTe. Electronic transport and in situ angle-resolved photoemission spectroscopy show the films are natively metallic with the Fermi level in the valence band and the band structure is in good agreement with first principles calculations for altermagnetic spin-splitting. Neutron diffraction confirms that the film is antiferromagnetic with planar anisotropy and polarized neutron reflectometry indicates weak ferromagnetism, which is linked to a slight Mn-richness that is intrinsic to the MBE grown samples. When combined with the anomalous Hall effect, this work shows that the electronic response is strongly affected by the ferromagnetic moment. Altogether, this highlights potential mechanisms for controlling altermagnetic ordering for diverse spintronic applications.
{"title":"Stoichiometry-induced ferromagnetism in altermagnetic candidate MnTe","authors":"Michael Chilcote, Alessandro R. Mazza, Qiangsheng Lu, Isaiah Gray, Qi Tian, Qinwen Deng, Duncan Moseley, An-Hsi Chen, Jason Lapano, Jason S. Gardner, Gyula Eres, T. Zac Ward, Erxi Feng, Huibo Cao, Valeria Lauter, Michael A. McGuire, Raphael Hermann, David Parker, Myung-Geun Han, Asghar Kayani, Gaurab Rimal, Liang Wu, Timothy R. Charlton, Robert G. Moore, Matthew Brahlek","doi":"arxiv-2406.04474","DOIUrl":"https://doi.org/arxiv-2406.04474","url":null,"abstract":"The field of spintronics has seen a surge of interest in altermagnetism due\u0000to novel predictions and many possible applications. MnTe is a leading\u0000altermagnetic candidate that is of significant interest across spintronics due\u0000to its layered antiferromagnetic structure, high Neel temperature (TN ~ 310 K)\u0000and semiconducting properties. We present results on molecular beam epitaxy\u0000(MBE) grown MnTe/InP(111) films. Here, it is found that the electronic and\u0000magnetic properties are driven by the natural stoichiometry of MnTe. Electronic\u0000transport and in situ angle-resolved photoemission spectroscopy show the films\u0000are natively metallic with the Fermi level in the valence band and the band\u0000structure is in good agreement with first principles calculations for\u0000altermagnetic spin-splitting. Neutron diffraction confirms that the film is\u0000antiferromagnetic with planar anisotropy and polarized neutron reflectometry\u0000indicates weak ferromagnetism, which is linked to a slight Mn-richness that is\u0000intrinsic to the MBE grown samples. When combined with the anomalous Hall\u0000effect, this work shows that the electronic response is strongly affected by\u0000the ferromagnetic moment. Altogether, this highlights potential mechanisms for\u0000controlling altermagnetic ordering for diverse spintronic applications.","PeriodicalId":501211,"journal":{"name":"arXiv - PHYS - Other Condensed Matter","volume":"51 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-06-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141500872","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Alberto Guandalini, Ryosuke Senga, Yung-Chang Lin, Kazu Suenaga, Paolo Barone, Francesco Mauri, Thomas Pichler, Christian Kramberger
In transmission electron energy-loss spectroscopy, the cross section in 2D is quenched by kinematic effects once the momentum transfer becomes smaller than a critical value set by $q_z$, the momentum loss parallel to the beam. Our highly momentum ($Delta q = 0.02$~r{A}$^{-1}$) and energy ($Delta E = 45$~meV) resolved setup is instrumental on delivering the unprecedented experimental verification of quenched 2D EEL spectra on freestanding graphene at momentum transfers $q$ below $0.06$r{A}$^{-1}$. We retrieve the intrinsic uniform dielectric response of graphene from measured spectra by quantifying the kinematic suppression.
在透射电子能量损失光谱学中，一旦动量传递小于$q_z$（平行于光束的动量损失）设定的临界值，二维截面就会因运动效应而淬灭。我们的高动量（$Delta q = 0.02$~r{A}$^{-1}$）和高能量（$Delta E = 45$~meV）解析装置有助于对独立石墨烯在动量传输低于$0.06$r{A}$^{-1}$时的淬火二维电子能谱进行前所未有的实验验证。我们通过量化运动抑制，从测量到的光谱中找回了石墨烯固有的均匀介电响应。
{"title":"Direct observation of the vanishing EELS cross section in graphene","authors":"Alberto Guandalini, Ryosuke Senga, Yung-Chang Lin, Kazu Suenaga, Paolo Barone, Francesco Mauri, Thomas Pichler, Christian Kramberger","doi":"arxiv-2406.02998","DOIUrl":"https://doi.org/arxiv-2406.02998","url":null,"abstract":"In transmission electron energy-loss spectroscopy, the cross section in 2D is\u0000quenched by kinematic effects once the momentum transfer becomes smaller than a\u0000critical value set by $q_z$, the momentum loss parallel to the beam. Our highly\u0000momentum ($Delta q = 0.02$~r{A}$^{-1}$) and energy ($Delta E = 45$~meV)\u0000resolved setup is instrumental on delivering the unprecedented experimental\u0000verification of quenched 2D EEL spectra on freestanding graphene at momentum\u0000transfers $q$ below $0.06$r{A}$^{-1}$. We retrieve the intrinsic uniform\u0000dielectric response of graphene from measured spectra by quantifying the\u0000kinematic suppression.","PeriodicalId":501211,"journal":{"name":"arXiv - PHYS - Other Condensed Matter","volume":"14 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-06-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141520116","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Victoria Vega Fernández, Alicia Estela Herguedas-Alonso, Javier Hermosa, Lucía Aballe, Andrea Sorrentino, Ricardo Valcarcel, Carlos Quiros, Jose Ignacio Martín, Eva Pereiro, Salvador Ferrer, Aurelio Hierro-Rodríguez, María Vélez
Bilayers of NdCo$_5$/Ni$_8$Fe$_2$ can act as reconfigurable racetracks thanks to the parallel stripe domain configuration present in the hard magnetic material with weak perpendicular anisotropy (NdCo$_5$), and its imprint on the soft magnetic layer (Ni$_8$Fe$_2$). This pattern hosts spin textures with well defined topological charges and establishes paths for their deterministic propagation under the effect of pulsed currents, which has been studied as a function of externally applied fields by using Magnetic Transmission X-ray Microscopy. The experiments show guided vortex/antivortex propagation events within the Ni$_8$Fe$_2$ above a threshold current of $3cdot10^{11}$ A/m$^2$. Opposite propagation senses have been observed depending on the topological charge of the spin texture, both in the remnant state and under an applied external field. Micromagnetic simulations of our multilayer reveal that the guiding effect and asymmetric propagation sense are due to the magnetic history of the hard magnetic layer. An exchange-bias-based memory effect acts as a magnetic spring and controls the propagation sense by favoring a specific orientation of the in plane magnetization, leading to a system which behaves as a hard-soft magnetic composite with reconfigurable capabilities for a controlled propagation of magnetic topological textures.
NdCo$_5$/Ni$_8$Fe$_2$ 的双层膜可以作为可重新配置的赛道，这要归功于具有弱垂直各向异性的硬磁性材料（NdCo$_5$）中存在的平行条纹畴构型及其在软磁层（Ni$_8$Fe$_2$）上的印记。利用磁透射 X 射线显微镜研究了这种模式作为外加磁场的函数所产生的具有明确拓扑电荷的自旋纹理，并为其在脉冲电流作用下的确定性传播建立了路径。实验结果表明，当阈值电流超过 $3cdot10^{11}$ A/m$^2$ 时，Ni$_8$Fe$_2$ 中会出现有向导的旋涡/反旋涡传播现象。对我们的多磁层进行的微磁模拟显示，引导效应和非对称传播感应是由硬磁层的磁性历史造成的。基于交换偏置的记忆效应就像磁性弹簧一样，通过偏向平面内磁化的特定方向来控制传播感，从而产生了一种表现为软硬磁性复合材料的系统，它具有可重新配置的能力，可以控制磁拓扑纹理的传播。
{"title":"Memory effects on the current induced propagation of spin textures in NdCo$_5$/Ni$_8$Fe$_2$ bilayers","authors":"Victoria Vega Fernández, Alicia Estela Herguedas-Alonso, Javier Hermosa, Lucía Aballe, Andrea Sorrentino, Ricardo Valcarcel, Carlos Quiros, Jose Ignacio Martín, Eva Pereiro, Salvador Ferrer, Aurelio Hierro-Rodríguez, María Vélez","doi":"arxiv-2406.01091","DOIUrl":"https://doi.org/arxiv-2406.01091","url":null,"abstract":"Bilayers of NdCo$_5$/Ni$_8$Fe$_2$ can act as reconfigurable racetracks thanks\u0000to the parallel stripe domain configuration present in the hard magnetic\u0000material with weak perpendicular anisotropy (NdCo$_5$), and its imprint on the\u0000soft magnetic layer (Ni$_8$Fe$_2$). This pattern hosts spin textures with well\u0000defined topological charges and establishes paths for their deterministic\u0000propagation under the effect of pulsed currents, which has been studied as a\u0000function of externally applied fields by using Magnetic Transmission X-ray\u0000Microscopy. The experiments show guided vortex/antivortex propagation events\u0000within the Ni$_8$Fe$_2$ above a threshold current of $3cdot10^{11}$ A/m$^2$.\u0000Opposite propagation senses have been observed depending on the topological\u0000charge of the spin texture, both in the remnant state and under an applied\u0000external field. Micromagnetic simulations of our multilayer reveal that the\u0000guiding effect and asymmetric propagation sense are due to the magnetic history\u0000of the hard magnetic layer. An exchange-bias-based memory effect acts as a\u0000magnetic spring and controls the propagation sense by favoring a specific\u0000orientation of the in plane magnetization, leading to a system which behaves as\u0000a hard-soft magnetic composite with reconfigurable capabilities for a\u0000controlled propagation of magnetic topological textures.","PeriodicalId":501211,"journal":{"name":"arXiv - PHYS - Other Condensed Matter","volume":"70 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-06-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141256505","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Yongzhang Shi, Chi Zhang, Zhenhui Hao, Changjun Jiang, C. K. Ong, Guozhi Chai
We investigated the magnon-photon coupling in an open cavity magnonic system, which leads to two different nonreciprocal singularities dominated by the dissipative coupling. One type of singularity is the exceptional point, which is just on the exceptional surface in parameter space. The other type of singularity is the bound state in the continuum discovered in the level-attraction-like coupling, which is above the exceptional surface. In experiment, we realized the two different singularities with nonreciprocity and selectivity in an open cavity magnonic system with suitable dissipation rating. Our results can be understood well with the pseudo-Hermitian theory of magnon-polariton system.
{"title":"Nonreciprocal singularities dominated by the dissipative photon-magnon coupling in non-Hermitian systems","authors":"Yongzhang Shi, Chi Zhang, Zhenhui Hao, Changjun Jiang, C. K. Ong, Guozhi Chai","doi":"arxiv-2405.17869","DOIUrl":"https://doi.org/arxiv-2405.17869","url":null,"abstract":"We investigated the magnon-photon coupling in an open cavity magnonic system,\u0000which leads to two different nonreciprocal singularities dominated by the\u0000dissipative coupling. One type of singularity is the exceptional point, which\u0000is just on the exceptional surface in parameter space. The other type of\u0000singularity is the bound state in the continuum discovered in the\u0000level-attraction-like coupling, which is above the exceptional surface. In\u0000experiment, we realized the two different singularities with nonreciprocity and\u0000selectivity in an open cavity magnonic system with suitable dissipation rating.\u0000Our results can be understood well with the pseudo-Hermitian theory of\u0000magnon-polariton system.","PeriodicalId":501211,"journal":{"name":"arXiv - PHYS - Other Condensed Matter","volume":"23 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-05-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141170264","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Josefine Enkner, Lorenzo Graziotto, Dalin Boriçi, Felice Appugliese, Christian Reichl, Giacomo Scalari, Nicolas Regnault, Werner Wegscheider, Cristiano Ciuti, Jérôme Faist
The magnetotransport of a high-mobility two-dimensional electron gas coupled to a hovering split-ring resonator with controllable distance is studied in the quantum Hall regime. The measurements reveal an enhancement by more than a factor 2 of the quantum Hall energy gaps at the fractional filling factors 4/3, 5/3, and 7/5, alongside a concurrent reduction in exchange splitting at odd integer filling factors. Theoretically, we show the strength of both effects to be quantitatively compatible with the emergence of an effective electron-electron long-range attractive interaction mediated by the exchange of virtual cavity photons in the presence of significant spatial gradients of the cavity electric vacuum fields. These results unveil a compelling interplay between cavity quantum electrodynamics and electronic correlations in two-dimensional systems, with profound implications for the manipulation and control of quantum phases in 2D materials.
{"title":"Enhanced fractional quantum Hall gaps in a two-dimensional electron gas coupled to a hovering split-ring resonator","authors":"Josefine Enkner, Lorenzo Graziotto, Dalin Boriçi, Felice Appugliese, Christian Reichl, Giacomo Scalari, Nicolas Regnault, Werner Wegscheider, Cristiano Ciuti, Jérôme Faist","doi":"arxiv-2405.18362","DOIUrl":"https://doi.org/arxiv-2405.18362","url":null,"abstract":"The magnetotransport of a high-mobility two-dimensional electron gas coupled\u0000to a hovering split-ring resonator with controllable distance is studied in the\u0000quantum Hall regime. The measurements reveal an enhancement by more than a\u0000factor 2 of the quantum Hall energy gaps at the fractional filling factors 4/3,\u00005/3, and 7/5, alongside a concurrent reduction in exchange splitting at odd\u0000integer filling factors. Theoretically, we show the strength of both effects to\u0000be quantitatively compatible with the emergence of an effective\u0000electron-electron long-range attractive interaction mediated by the exchange of\u0000virtual cavity photons in the presence of significant spatial gradients of the\u0000cavity electric vacuum fields. These results unveil a compelling interplay\u0000between cavity quantum electrodynamics and electronic correlations in\u0000two-dimensional systems, with profound implications for the manipulation and\u0000control of quantum phases in 2D materials.","PeriodicalId":501211,"journal":{"name":"arXiv - PHYS - Other Condensed Matter","volume":"133 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-05-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141170798","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Lane E. Schultz, Yiqi Wang, Ryan Jacobs, Dane Morgan
Knowledge of the domain of applicability of a machine learning model is essential to ensuring accurate and reliable model predictions. In this work, we develop a new approach of assessing model domain and demonstrate that our approach provides accurate and meaningful designation of in-domain versus out-of-domain when applied across multiple model types and material property data sets. Our approach assesses the distance between a test and training data point in feature space by using kernel density estimation and shows that this distance provides an effective tool for domain determination. We show that chemical groups considered unrelated based on established chemical knowledge exhibit significant dissimilarities by our measure. We also show that high measures of dissimilarity are associated with poor model performance (i.e., high residual magnitudes) and poor estimates of model uncertainty (i.e., unreliable uncertainty estimation). Automated tools are provided to enable researchers to establish acceptable dissimilarity thresholds to identify whether new predictions of their own machine learning models are in-domain versus out-of-domain.
{"title":"Determining Domain of Machine Learning Models using Kernel Density Estimates: Applications in Materials Property Prediction","authors":"Lane E. Schultz, Yiqi Wang, Ryan Jacobs, Dane Morgan","doi":"arxiv-2406.05143","DOIUrl":"https://doi.org/arxiv-2406.05143","url":null,"abstract":"Knowledge of the domain of applicability of a machine learning model is\u0000essential to ensuring accurate and reliable model predictions. In this work, we\u0000develop a new approach of assessing model domain and demonstrate that our\u0000approach provides accurate and meaningful designation of in-domain versus\u0000out-of-domain when applied across multiple model types and material property\u0000data sets. Our approach assesses the distance between a test and training data\u0000point in feature space by using kernel density estimation and shows that this\u0000distance provides an effective tool for domain determination. We show that\u0000chemical groups considered unrelated based on established chemical knowledge\u0000exhibit significant dissimilarities by our measure. We also show that high\u0000measures of dissimilarity are associated with poor model performance (i.e.,\u0000high residual magnitudes) and poor estimates of model uncertainty (i.e.,\u0000unreliable uncertainty estimation). Automated tools are provided to enable\u0000researchers to establish acceptable dissimilarity thresholds to identify\u0000whether new predictions of their own machine learning models are in-domain\u0000versus out-of-domain.","PeriodicalId":501211,"journal":{"name":"arXiv - PHYS - Other Condensed Matter","volume":"63 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-05-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141531457","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Recently, Xu et al. introduced the concept of an interband character for a time-dependent quantum system. This quantity is gauge invariant and quantized as integer values, analogous to the Euler characteristic based on the Gauss-Bonnet theorem for a manifold with a smooth boundary. In this work, we find that the geometric shift vector in momentum space from shift currents in the bulk photovoltaic effect is equivalent to the quantum geometric potential and plays the role of geodesic curvature, that is, of a quantum system whose parameter space is the Bloch momentum. We reveal the intricate relationships among geometric quantities such as the shift vector, Berry curvature, and quantum metric. Additionally, we present the Wilson representation for the quantized interband character and extend our analysis to bosonic photon and phonon drag shift vectors with non-vertical transitions. The application of Wilson loop method facilitates first-principles calculations, providing insights into the geometric underpinnings of these interband gauge invariant quantities and shedding light on their nonlinear optical manifestations in real materials.
{"title":"Geodesic nature and quantization of shift vector","authors":"Hua Wang, Kai Chang","doi":"arxiv-2405.13355","DOIUrl":"https://doi.org/arxiv-2405.13355","url":null,"abstract":"Recently, Xu et al. introduced the concept of an interband character for a\u0000time-dependent quantum system. This quantity is gauge invariant and quantized\u0000as integer values, analogous to the Euler characteristic based on the\u0000Gauss-Bonnet theorem for a manifold with a smooth boundary. In this work, we\u0000find that the geometric shift vector in momentum space from shift currents in\u0000the bulk photovoltaic effect is equivalent to the quantum geometric potential\u0000and plays the role of geodesic curvature, that is, of a quantum system whose\u0000parameter space is the Bloch momentum. We reveal the intricate relationships\u0000among geometric quantities such as the shift vector, Berry curvature, and\u0000quantum metric. Additionally, we present the Wilson representation for the\u0000quantized interband character and extend our analysis to bosonic photon and\u0000phonon drag shift vectors with non-vertical transitions. The application of\u0000Wilson loop method facilitates first-principles calculations, providing\u0000insights into the geometric underpinnings of these interband gauge invariant\u0000quantities and shedding light on their nonlinear optical manifestations in real\u0000materials.","PeriodicalId":501211,"journal":{"name":"arXiv - PHYS - Other Condensed Matter","volume":"58 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-05-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141146426","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Haruki Takezawa, Han Hsu, Kei Hirose, Fumiya Sakai, Suyu Fu, Hitoshi Gomi
While helium is a representative noble gas element characterized by its chemical inertness at ambient conditions, recent experiments and calculations argued that a minor amount of helium is incorporated into molten iron from silicate under high pressures. Here we examined the reaction between iron and helium at 8-42 GPa and ~1000-2820 K and found remarkable volume expansion of the Fe lattice, which is attributed to the formations of fcc and distorted hcp iron-helium compounds with x in FeHex up to 0.13 and 0.42, respectively. Upon releasing pressure under room temperature, these fcc and distorted hcp FeHex were still observed while the former lost some helium. In addition, our first-principles calculations indicate that fcc FeHe0.25, with He atoms in the tetrahedral interstitial sites, is dynamically stable in different magnetic states throughout 0-50 GPa. These results support that the Earth's core can be a large reservoir of primordial 3He.
氦气是一种具有代表性的惰性惰性惰性气体元素，最近的实验和计算表明，在高压条件下，硅酸盐熔融铁中会掺入少量氦气。在这里，我们研究了铁和氦在 8-42 GPa 和 ~1000-2820 K 下的反应，发现铁晶格的体积显著膨胀，这归因于形成了 fcc 和扭曲的 hc 氦化合物，FeHex 中的 x 分别高达 0.13 和 0.42。在室温下释放压力时，仍然可以观察到这些 fcc 和扭曲的 hcp FeHex，而前者则失去了一些氦。此外，我们的第一性原理计算表明，在 0-50 GPa 的不同磁态下，FeHe0.25 的四面体间隙位点中含有氦原子的 fcc FeHe0.25 具有动态稳定性。这些结果支持地核可能是原始 3He 的一个大型储藏库。
{"title":"Formation of Iron-Helium Compounds under High Pressure","authors":"Haruki Takezawa, Han Hsu, Kei Hirose, Fumiya Sakai, Suyu Fu, Hitoshi Gomi","doi":"arxiv-2405.11810","DOIUrl":"https://doi.org/arxiv-2405.11810","url":null,"abstract":"While helium is a representative noble gas element characterized by its\u0000chemical inertness at ambient conditions, recent experiments and calculations\u0000argued that a minor amount of helium is incorporated into molten iron from\u0000silicate under high pressures. Here we examined the reaction between iron and\u0000helium at 8-42 GPa and ~1000-2820 K and found remarkable volume expansion of\u0000the Fe lattice, which is attributed to the formations of fcc and distorted hcp\u0000iron-helium compounds with x in FeHex up to 0.13 and 0.42, respectively. Upon\u0000releasing pressure under room temperature, these fcc and distorted hcp FeHex\u0000were still observed while the former lost some helium. In addition, our\u0000first-principles calculations indicate that fcc FeHe0.25, with He atoms in the\u0000tetrahedral interstitial sites, is dynamically stable in different magnetic\u0000states throughout 0-50 GPa. These results support that the Earth's core can be\u0000a large reservoir of primordial 3He.","PeriodicalId":501211,"journal":{"name":"arXiv - PHYS - Other Condensed Matter","volume":"24 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-05-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141146460","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
In this thesis we develop methods for many-body open quantum systems and apply them to systems of organic polaritons. The methods employ a mean-field approach to reduce the dimensionality of large-scale problems. Initially assuming the absence of correlations in the many-body state, this approach is built upon in two ways. First, we show how the mean-field approximation can be combined with matrix product operator methods to efficiently simulate the non-Markovian dynamics of a many-body system with strong coupling to multiple environments. We apply this method to calculate the threshold and photoluminescence for a realistic model of an organic laser. Second, we extend the mean-field description by systematically including higher-order correlations via cumulant expansions of the Heisenberg equations of motion. We investigate the validity and convergence properties of these expansions, both with respect to expansion order and system size, for many-body systems with many-to-one network structures. We then show how the cumulant expansions may be used to calculate spatially resolved dynamics of organic polaritons. This enables a study of organic polariton transport in which we observe reversible conversion to dark exciton states and sub-group-velocity propagation. The methods established in this work offer versatile tools for analysing large, many-body open quantum systems and investigating finite-size effects. Their application reveals the intricate dynamics of organic polaritons resulting from the interplay of strong light-matter coupling and vibrational effects.
{"title":"Mean-field and cumulant approaches to modelling organic polariton physics","authors":"Piper Fowler-Wright","doi":"arxiv-2405.09812","DOIUrl":"https://doi.org/arxiv-2405.09812","url":null,"abstract":"In this thesis we develop methods for many-body open quantum systems and\u0000apply them to systems of organic polaritons. The methods employ a mean-field\u0000approach to reduce the dimensionality of large-scale problems. Initially\u0000assuming the absence of correlations in the many-body state, this approach is\u0000built upon in two ways. First, we show how the mean-field approximation can be combined with matrix\u0000product operator methods to efficiently simulate the non-Markovian dynamics of\u0000a many-body system with strong coupling to multiple environments. We apply this\u0000method to calculate the threshold and photoluminescence for a realistic model\u0000of an organic laser. Second, we extend the mean-field description by systematically including\u0000higher-order correlations via cumulant expansions of the Heisenberg equations\u0000of motion. We investigate the validity and convergence properties of these\u0000expansions, both with respect to expansion order and system size, for many-body\u0000systems with many-to-one network structures. We then show how the cumulant\u0000expansions may be used to calculate spatially resolved dynamics of organic\u0000polaritons. This enables a study of organic polariton transport in which we\u0000observe reversible conversion to dark exciton states and sub-group-velocity\u0000propagation. The methods established in this work offer versatile tools for analysing\u0000large, many-body open quantum systems and investigating finite-size effects.\u0000Their application reveals the intricate dynamics of organic polaritons\u0000resulting from the interplay of strong light-matter coupling and vibrational\u0000effects.","PeriodicalId":501211,"journal":{"name":"arXiv - PHYS - Other Condensed Matter","volume":"3 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-05-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141059901","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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