Pub Date : 2021-06-26DOI: 10.1103/PhysRevMaterials.5.104409
Seong-Hoon Jang, Y. Motome
We theoretically investigate the electronic band structures and magnetic properties of ilmenites with edge-sharing IrO$_6$ honeycomb layers, $A$IrO$_3$ with $A=$ Mg, Zn, and Mn, in comparison with a collinear antiferromagnet MnTiO$_3$. The compounds with $A=$ Mg and Zn were recently reported in Y.~Haraguchi {it et al.}, Phys. Rev. Materials {bf 2}, 054411 (2018), while MnIrO$_3$ has not been synthesized yet but the honeycomb stacking structure was elaborated in a superlattice with MnTiO$_3$ in K.~Miura {it et al.}, Commun. Mater. {bf 1}, 55 (2020). We find that, in contrast to MnTiO$_3$, where an energy gap opens in the Ti $3d$ bands by antiferromagnetic ordering of the high-spin $S=5/2$ moments, MgIrO$_3$ and ZnIrO$_3$ have a gap in the Ir $5d$ bands under the influence of both spin-orbit coupling and electron correlation. Their electronic structures are similar to those in the spin-orbit coupled Mott insulators with the $j_{rm eff}=1/2$ pseudospin degree of freedom, as found in monoclinic $A_2$IrO$_3$ with $A=$ Na and Li which have been studied as candidates for the Kitaev spin liquid. Indeed, we find that the effective exchange interactions between the $j_{rm eff}=1/2$ pseudospins are dominated by the Kitaev-type bond-dependent interaction and the symmetric off-diagonal interactions. On the other hand, for MnIrO$_3$, we show that the local lattice structure is largely deformed, and both Mn $3d$ and Ir $5d$ bands appear near the Fermi level in a complicated manner, which makes the electronic and magnetic properties qualitatively different from MgIrO$_3$ and ZnIrO$_3$. Our results indicate that the IrO$_6$ honeycomb network in the ilmenites $A$IrO$_3$ with $A=$ Mg and Zn would offer a good platform for exotic magnetism by the spin-orbital entangled moments like the Kitaev spin liquid.
{"title":"Electronic and magnetic properties of iridium ilmenites $A$IrO$_3$ ($A=$ Mg, Zn, and Mn).","authors":"Seong-Hoon Jang, Y. Motome","doi":"10.1103/PhysRevMaterials.5.104409","DOIUrl":"https://doi.org/10.1103/PhysRevMaterials.5.104409","url":null,"abstract":"We theoretically investigate the electronic band structures and magnetic properties of ilmenites with edge-sharing IrO$_6$ honeycomb layers, $A$IrO$_3$ with $A=$ Mg, Zn, and Mn, in comparison with a collinear antiferromagnet MnTiO$_3$. The compounds with $A=$ Mg and Zn were recently reported in Y.~Haraguchi {it et al.}, Phys. Rev. Materials {bf 2}, 054411 (2018), while MnIrO$_3$ has not been synthesized yet but the honeycomb stacking structure was elaborated in a superlattice with MnTiO$_3$ in K.~Miura {it et al.}, Commun. Mater. {bf 1}, 55 (2020). We find that, in contrast to MnTiO$_3$, where an energy gap opens in the Ti $3d$ bands by antiferromagnetic ordering of the high-spin $S=5/2$ moments, MgIrO$_3$ and ZnIrO$_3$ have a gap in the Ir $5d$ bands under the influence of both spin-orbit coupling and electron correlation. Their electronic structures are similar to those in the spin-orbit coupled Mott insulators with the $j_{rm eff}=1/2$ pseudospin degree of freedom, as found in monoclinic $A_2$IrO$_3$ with $A=$ Na and Li which have been studied as candidates for the Kitaev spin liquid. Indeed, we find that the effective exchange interactions between the $j_{rm eff}=1/2$ pseudospins are dominated by the Kitaev-type bond-dependent interaction and the symmetric off-diagonal interactions. On the other hand, for MnIrO$_3$, we show that the local lattice structure is largely deformed, and both Mn $3d$ and Ir $5d$ bands appear near the Fermi level in a complicated manner, which makes the electronic and magnetic properties qualitatively different from MgIrO$_3$ and ZnIrO$_3$. Our results indicate that the IrO$_6$ honeycomb network in the ilmenites $A$IrO$_3$ with $A=$ Mg and Zn would offer a good platform for exotic magnetism by the spin-orbital entangled moments like the Kitaev spin liquid.","PeriodicalId":8511,"journal":{"name":"arXiv: Strongly Correlated Electrons","volume":"51 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2021-06-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"91170532","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}
Pub Date : 2021-05-26DOI: 10.21203/RS.3.RS-569113/V1
M. Fabrizio
In periodic systems of interacting electrons, Fermi and Luttinger surfaces refer to the locations within the Brillouin zone of poles and zeros, respectively, of the single-particle Green's function at zero energy and temperature. Such difference in analytic properties underlies the emergence of well-defined quasiparticles close to a Fermi surface, in contrast to their supposed non-existence close to a Luttinger surface, where the single-particle density-of-states vanishes at zero energy. We here show that, contrary to such common belief, coherent `quasiparticles` do exist also approaching a Luttinger surface in compressible interacting electron systems. Thermodynamic and dynamic properties of such `quasiparticles` are just those of conventional ones. For instance, they yield well defined quantum oscillations in Luttinger's surface and linear in temperature specific heat, which is striking given the vanishing density of states of physical electrons, but actually not uncommon in strongly correlated materials.
{"title":"Landau-Fermi liquids in disguise","authors":"M. Fabrizio","doi":"10.21203/RS.3.RS-569113/V1","DOIUrl":"https://doi.org/10.21203/RS.3.RS-569113/V1","url":null,"abstract":"\u0000 In periodic systems of interacting electrons, Fermi and Luttinger surfaces refer to the locations within the Brillouin zone of poles and zeros, respectively, of the single-particle Green's function at zero energy and temperature. Such difference in analytic properties underlies the emergence of well-defined quasiparticles close to a Fermi surface, in contrast to their supposed non-existence close to a Luttinger surface, where the single-particle density-of-states vanishes at zero energy. \u0000We here show that, contrary to such common belief, coherent `quasiparticles` do exist also approaching a Luttinger surface in compressible interacting electron systems. Thermodynamic and dynamic properties of such `quasiparticles` are just those of conventional ones. For instance, they yield well defined quantum oscillations \u0000in Luttinger's surface and linear in temperature specific heat, which is striking given the vanishing density of states of physical electrons, but actually not uncommon in strongly correlated materials.","PeriodicalId":8511,"journal":{"name":"arXiv: Strongly Correlated Electrons","volume":"22 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2021-05-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"74602344","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}
Pub Date : 2021-04-15DOI: 10.1103/PhysRevB.103.L241107
P. Prelovšek, J. Herbrych
We present an extended microcanonical Lanczos method (MCLM) for a direct evaluation of the diffusion constant and its frequency dependence within the disordered Anderson model of noninteracting particles. The method allows to study systems beyond $10^6$ sites and we present results for diffusion in hypercubic lattices in $ d = 3- 7$ dimensions. Below the transition to localization, where we confirm dynamical scaling behaviour, of interest is a wide region of incoherent diffusion, similar to percolating phenomena and to interacting many-body localized systems.
我们提出了一种扩展的微规范Lanczos方法(MCLM)，用于直接评估非相互作用粒子的无序安德森模型中的扩散常数及其频率依赖性。该方法允许研究超过$10^6$位的系统，我们给出了在$ d = 3- $ 7$维的超立方晶格中的扩散结果。在向局部化过渡的下面，我们确认了动态标度行为，我们感兴趣的是一个广泛的非相干扩散区域，类似于渗透现象和相互作用的多体局部化系统。
{"title":"Diffusion in the Anderson model in higher dimensions","authors":"P. Prelovšek, J. Herbrych","doi":"10.1103/PhysRevB.103.L241107","DOIUrl":"https://doi.org/10.1103/PhysRevB.103.L241107","url":null,"abstract":"We present an extended microcanonical Lanczos method (MCLM) for a direct evaluation of the diffusion constant and its frequency dependence within the disordered Anderson model of noninteracting particles. The method allows to study systems beyond $10^6$ sites and we present results for diffusion in hypercubic lattices in $ d = 3- 7$ dimensions. Below the transition to localization, where we confirm dynamical scaling behaviour, of interest is a wide region of incoherent diffusion, similar to percolating phenomena and to interacting many-body localized systems.","PeriodicalId":8511,"journal":{"name":"arXiv: Strongly Correlated Electrons","volume":"24 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2021-04-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"72894662","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}
Pub Date : 2021-04-02DOI: 10.21203/RS.3.RS-351743/V1
Yanxing Yang, Cheng Tan, Zihao Zhu, Jing Zhang, Z. Ding, Qiong Wu, Changshen Chen, T. Shiroka, Douglas MacLaughline, C. Varma, L. Shu
Quantum fluctuations are expected to lead to highly entangled spin-liquid states in some two-dimensional spin-1/2 compounds. We have synthesized and measured thermodynamic properties and muon relaxation rates in two related such compounds, one of which is the least disordered of this kind synthesized hitherto and reveals intrinsic properties of a class of spin-liquids. Its measured properties can all be simply characterized by scale invariant time-dependent fluctuations with a single parameter. The specific heat divided by temperature and muon relaxation rates are both temperature independent at low temperatures, followed by a logarithmic decrease with increasing temperature. Even more remarkably, ∼57% of the magnetic entropy is missing down to temperatures of O(10−3) the exchange energy, independent of magnetic field up to gµBH > kBT . This is evidence that quantum fluctuations lead either to a gigantic specific heat peak from topological singlet excitations below such temperatures, or to an extensively degenerate topological singlet ground state. These results reveal an ultra-quantum state of matter.
{"title":"Discovery of an ultra-quantum spin liquid","authors":"Yanxing Yang, Cheng Tan, Zihao Zhu, Jing Zhang, Z. Ding, Qiong Wu, Changshen Chen, T. Shiroka, Douglas MacLaughline, C. Varma, L. Shu","doi":"10.21203/RS.3.RS-351743/V1","DOIUrl":"https://doi.org/10.21203/RS.3.RS-351743/V1","url":null,"abstract":"\u0000 Quantum fluctuations are expected to lead to highly entangled spin-liquid states in some two-dimensional spin-1/2 compounds. We have synthesized and measured thermodynamic properties and muon relaxation rates in two related such compounds, one of which is the least disordered of this kind synthesized hitherto and reveals intrinsic properties of a class of spin-liquids. Its measured properties can all be simply characterized by scale invariant time-dependent fluctuations with a single parameter. The specific heat divided by temperature and muon relaxation rates are both temperature independent at low temperatures, followed by a logarithmic decrease with increasing temperature. Even more remarkably, ∼57% of the magnetic entropy is missing down to temperatures of O(10−3) the exchange energy, independent of magnetic field up to gµBH > kBT . This is evidence that quantum fluctuations lead either to a gigantic specific heat peak from topological singlet excitations below such temperatures, or to an extensively degenerate topological singlet ground state. These results reveal an ultra-quantum state of matter.","PeriodicalId":8511,"journal":{"name":"arXiv: Strongly Correlated Electrons","volume":"7 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2021-04-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"88830338","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}
The study of topological magnetic excitations has attracted widespread attention in the past few years. In this thesis, I have studied some examples of novel topological magnonic phases/phenomena in low-dimensional quantum magnets. The first chapter motivates the research based on the research gap in this field of study. The second chapter is written to make the thesis self-sufficient and the concepts are explained through examples. In the second chapter, the following formalisms and physical observables are described: Holstein-Primakoff, bond operator, Schwinger boson, Bogoliubov-Valatin, Group theory, Berry-phase, Berry-curvature, Chern number, thermal Hall conductance, Nernst conductivity, dynamical spin structure factor, edge-current. The main results of the thesis are shown in the third, fourth, and fifth chapters. In the third chapter, I have shown that anti-chiral edge states (co-propagating edge states) arise in the ferromagnetic Heisenberg model on the honeycomb lattice with Dzyaloshinskii-Moriya (DM) interactions. My results suggest that such anti-chiral edge states may be induced in certain realistic models of quantum magnets. In the fourth chapter, I have found the emergence of many magnon band-topological phases in the flux state of the Shastry-Sutherland model. I have derived a simple analytical form of the temperature dependence of derivative of thermal Hall conductivity near the band topological transition point which I propose to be experimentally useful. In the fifth chapter, I have investigated the emergence of Weyl triplons due to inter-layer DM-interaction in a microscopic model of SrCu2(BO3)2, a widely studied frustrated quantum magnet. I have shown that the thermal magnon Hall conductivity has a quasi-linear dependence as a function of the magnetic field in a Weyl-triplon region.
{"title":"Topological excitations in quasi two-dimensional quantum magnets with weak interlayer interactions","authors":"D. Bhowmick","doi":"10.32657/10356/146503","DOIUrl":"https://doi.org/10.32657/10356/146503","url":null,"abstract":"The study of topological magnetic excitations has attracted widespread attention in the past few years. In this thesis, I have studied some examples of novel topological magnonic phases/phenomena in low-dimensional quantum magnets. The first chapter motivates the research based on the research gap in this field of study. The second chapter is written to make the thesis self-sufficient and the concepts are explained through examples. In the second chapter, the following formalisms and physical observables are described: Holstein-Primakoff, bond operator, Schwinger boson, Bogoliubov-Valatin, Group theory, Berry-phase, Berry-curvature, Chern number, thermal Hall conductance, Nernst conductivity, dynamical spin structure factor, edge-current. The main results of the thesis are shown in the third, fourth, and fifth chapters. In the third chapter, I have shown that anti-chiral edge states (co-propagating edge states) arise in the ferromagnetic Heisenberg model on the honeycomb lattice with Dzyaloshinskii-Moriya (DM) interactions. My results suggest that such anti-chiral edge states may be induced in certain realistic models of quantum magnets. In the fourth chapter, I have found the emergence of many magnon band-topological phases in the flux state of the Shastry-Sutherland model. I have derived a simple analytical form of the temperature dependence of derivative of thermal Hall conductivity near the band topological transition point which I propose to be experimentally useful. In the fifth chapter, I have investigated the emergence of Weyl triplons due to inter-layer DM-interaction in a microscopic model of SrCu2(BO3)2, a widely studied frustrated quantum magnet. I have shown that the thermal magnon Hall conductivity has a quasi-linear dependence as a function of the magnetic field in a Weyl-triplon region.","PeriodicalId":8511,"journal":{"name":"arXiv: Strongly Correlated Electrons","volume":"73 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2021-02-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"75983726","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}
Pub Date : 2021-02-08DOI: 10.1103/PHYSREVB.103.155103
Ajit C. Balram
We consider the fractional quantum Hall effect at the filling factor $nu=4/11$, where two independent experiments have observed a well-developed and quantized Hall plateau. We examine the Abelian state described by the "$4bar{2}1^{3}$" parton wave function and numerically demonstrate it to be a plausible candidate for the ground state at $nu=4/11$. We work out the low-energy effective theory of the $4bar{2}1^{3}$ edge and make predictions for experimentally measurable properties of the state.
{"title":"Abelian parton state for the \u0000ν=4/11\u0000 fractional quantum Hall effect","authors":"Ajit C. Balram","doi":"10.1103/PHYSREVB.103.155103","DOIUrl":"https://doi.org/10.1103/PHYSREVB.103.155103","url":null,"abstract":"We consider the fractional quantum Hall effect at the filling factor $nu=4/11$, where two independent experiments have observed a well-developed and quantized Hall plateau. We examine the Abelian state described by the \"$4bar{2}1^{3}$\" parton wave function and numerically demonstrate it to be a plausible candidate for the ground state at $nu=4/11$. We work out the low-energy effective theory of the $4bar{2}1^{3}$ edge and make predictions for experimentally measurable properties of the state.","PeriodicalId":8511,"journal":{"name":"arXiv: Strongly Correlated Electrons","volume":"23 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2021-02-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"81399928","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}
Pub Date : 2020-12-17DOI: 10.1103/PHYSREVMATERIALS.5.044803
F. Lechermann
The novel nickelate superconductors of infinite-layer type feature challenging electronic pecularities in the normal-state phase diagram with doping. Distinct many-body behavior and different dispersion regimes of the entangled ${$Ni-$d_{z^2}$, Ni-$d_{x^2-y^2}$$}$ orbital sector give rise to highly rich physics, which is here studied for the case of the NdNiO$_2$ system. An analysis based on advanced realistic dynamical mean-field theory unveils that the superconducting hole-doped region is the meeting place of a (self-)doped Mott insulator from the underdoped side, and a bad Hund metal from the overdoped side. Fermi-level crossing of the Ni-$d_{z^2}$ flat-band ties both regimes together to form a singular arena for unconventional superconductivity. We furthermore shed light on the intriguing problem of elusive magnetism in infinite-layer nickelates. Antiferromagnetic (AFM) order with small Ni moments is shown to be a vital competitor at low temperature. At stoichiometry, C-AFM order with ferro-alignment along the $c$-axis benefits from a conceivable coexistence with Kondo(-lattice) screening, whereas N{e}el-type G-AFM order has to be faced for dopings where superconductivity prevails.
{"title":"Doping-dependent character and possible magnetic ordering of \u0000NdNiO2","authors":"F. Lechermann","doi":"10.1103/PHYSREVMATERIALS.5.044803","DOIUrl":"https://doi.org/10.1103/PHYSREVMATERIALS.5.044803","url":null,"abstract":"The novel nickelate superconductors of infinite-layer type feature challenging electronic pecularities in the normal-state phase diagram with doping. Distinct many-body behavior and different dispersion regimes of the entangled ${$Ni-$d_{z^2}$, Ni-$d_{x^2-y^2}$$}$ orbital sector give rise to highly rich physics, which is here studied for the case of the NdNiO$_2$ system. An analysis based on advanced realistic dynamical mean-field theory unveils that the superconducting hole-doped region is the meeting place of a (self-)doped Mott insulator from the underdoped side, and a bad Hund metal from the overdoped side. Fermi-level crossing of the Ni-$d_{z^2}$ flat-band ties both regimes together to form a singular arena for unconventional superconductivity. We furthermore shed light on the intriguing problem of elusive magnetism in infinite-layer nickelates. Antiferromagnetic (AFM) order with small Ni moments is shown to be a vital competitor at low temperature. At stoichiometry, C-AFM order with ferro-alignment along the $c$-axis benefits from a conceivable coexistence with Kondo(-lattice) screening, whereas N{e}el-type G-AFM order has to be faced for dopings where superconductivity prevails.","PeriodicalId":8511,"journal":{"name":"arXiv: Strongly Correlated Electrons","volume":"46 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2020-12-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"88852457","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}
Pub Date : 2020-12-16DOI: 10.1103/PhysRevB.103.115144
A. James, M. Sekania, S. Dugdale, L. Chioncel
We calculated the magnetic Compton profiles (MCPs) of Ni using density functional theory supplemented by electronic correlations treated within dynamical mean-field theory (DMFT). We present comparisons between the theoretical and experimental MCPs. The theoretical MCPs were calculated using the KKR method with the perturbative spin-polarized T-matrix fluctuation exchange approximation DMFT solver, as well as with the full potential linear augmented planewave method with the numerically exact continuous-time quantum Monte Carlo DMFT solver. We show that the total magnetic moment decreases with the intra-atomic Coulomb repulsion $U$, which is also reflected in the corresponding MCPs. The total magnetic moment obtained in experimental measurements can be reproduced by intermediate values of $U$. The spectral function reveals that the minority X$_2$ Fermi surface pocket shrinks and gets shallower with respect to the density functional theory calculations.
{"title":"Magnetic Compton profiles of Ni beyond the one-particle picture: Numerically exact and perturbative solvers of dynamical mean-field theory","authors":"A. James, M. Sekania, S. Dugdale, L. Chioncel","doi":"10.1103/PhysRevB.103.115144","DOIUrl":"https://doi.org/10.1103/PhysRevB.103.115144","url":null,"abstract":"We calculated the magnetic Compton profiles (MCPs) of Ni using density functional theory supplemented by electronic correlations treated within dynamical mean-field theory (DMFT). We present comparisons between the theoretical and experimental MCPs. The theoretical MCPs were calculated using the KKR method with the perturbative spin-polarized T-matrix fluctuation exchange approximation DMFT solver, as well as with the full potential linear augmented planewave method with the numerically exact continuous-time quantum Monte Carlo DMFT solver. We show that the total magnetic moment decreases with the intra-atomic Coulomb repulsion $U$, which is also reflected in the corresponding MCPs. The total magnetic moment obtained in experimental measurements can be reproduced by intermediate values of $U$. The spectral function reveals that the minority X$_2$ Fermi surface pocket shrinks and gets shallower with respect to the density functional theory calculations.","PeriodicalId":8511,"journal":{"name":"arXiv: Strongly Correlated Electrons","volume":"39 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2020-12-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"81455619","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}
Pub Date : 2020-12-15DOI: 10.1103/PHYSREVB.103.064414
O. Utesov
Motivated by recent experimental results on GdRu$_2$Si$_2$ [Khanh, N.D., Nakajima, T., Yu, X. et al., emph{Nat. Nanotechnol.} textbf{15}, 444-449 (2020)], where nanometric square skyrmion lattice was observed, we propose simple analytical mean-field description of the high-temperature part of the phase diagram of centrosymmetric tetragonal frustrated antiferromagnets with dipolar interaction in the external magnetic field. In the reciprocal space dipolar forces provide momentum dependent biaxial anisotropy. It is shown that in tetragonal lattice in the large part of the Brillouin zone for mutually perpendicular modulation vectors in the $ab$ plane this anisotropy has mutually perpendicular easy axes and collinear middle axes, what leads to double-Q modulated spin structure stabilization. The latter turns out to be a square skyrmion lattice in the large part of its stability region with the topological charge $pm 1$ per magnetic unit cell, which is determined by the frustrated exchange coupling, and, thus, nanometer-sized. In the presence of additional single-ion easy-axis anisotropy, easy and middle axes can be swapped, which leads to different phase diagram. It is argued that the latter case is relevant to GdRu$_2$Si$_2$.
受最近在GdRu $_2$ Si $_2$上的实验结果的启发[Khanh, N.D, Nakajima, T.， Yu, X. et alemph{.， Nat}textbf{. nanotechnology . 15}, 444-449(2020)]，其中观察到纳米方形skyrmion晶格，我们提出了对偶极相互作用的中心对称四边形反铁磁体相图高温部分的简单解析平均场描述。在互反空间中，偶极力提供动量依赖的双轴各向异性。结果表明，对于$ab$平面上相互垂直的调制矢量，在布里温区大部分的四方晶格中，各向异性具有相互垂直的易轴和共线的中轴，从而导致双q调制自旋结构的稳定。后者在其稳定区域的大部分是正方形的skyrmion晶格，每个磁单元胞的拓扑电荷为$pm 1$，这是由受挫的交换耦合决定的，因此是纳米级的。在单离子易轴各向异性存在的情况下，易轴和中轴可以互换，从而得到不同的相图。本文认为后一种情况与gdp相关$_2$ Si $_2$。
{"title":"Thermodynamically stable skyrmion lattice in a tetragonal frustrated antiferromagnet with dipolar interaction","authors":"O. Utesov","doi":"10.1103/PHYSREVB.103.064414","DOIUrl":"https://doi.org/10.1103/PHYSREVB.103.064414","url":null,"abstract":"Motivated by recent experimental results on GdRu$_2$Si$_2$ [Khanh, N.D., Nakajima, T., Yu, X. et al., emph{Nat. Nanotechnol.} textbf{15}, 444-449 (2020)], where nanometric square skyrmion lattice was observed, we propose simple analytical mean-field description of the high-temperature part of the phase diagram of centrosymmetric tetragonal frustrated antiferromagnets with dipolar interaction in the external magnetic field. In the reciprocal space dipolar forces provide momentum dependent biaxial anisotropy. It is shown that in tetragonal lattice in the large part of the Brillouin zone for mutually perpendicular modulation vectors in the $ab$ plane this anisotropy has mutually perpendicular easy axes and collinear middle axes, what leads to double-Q modulated spin structure stabilization. The latter turns out to be a square skyrmion lattice in the large part of its stability region with the topological charge $pm 1$ per magnetic unit cell, which is determined by the frustrated exchange coupling, and, thus, nanometer-sized. In the presence of additional single-ion easy-axis anisotropy, easy and middle axes can be swapped, which leads to different phase diagram. It is argued that the latter case is relevant to GdRu$_2$Si$_2$.","PeriodicalId":8511,"journal":{"name":"arXiv: Strongly Correlated Electrons","volume":"49 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2020-12-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"86760369","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}
Pub Date : 2020-12-15DOI: 10.1103/physrevb.103.155147
L. Engström, T. Pereg-Barnea, W. Witczak-Krempa
We present a comprehensive study of a three-orbital lattice model suitable for the layered iridate Sr2IrO4. Our analysis includes various on-site interactions (including Hubbard and Hund's) as well as compressive strain, and a Zeeman magnetic field. We use a self-consistent mean field approach with multiple order parameters to characterize the resulting phases. While in some parameter regimes the compound is well described by an effective J=1/2 model, in other regimes the full multiorbital description is needed. As a function of the compressive strain, we uncover two quantum phase transitions: first a continuous metal-insulator transition, and subsequently a first order magnetic melting of the antiferromagnetic order. Crucially, bands of both J=1/2 and J=3/2 nature play important roles in these transitions. Our results qualitatively agree with experiments of Sr2IrO4 under strain induced by a substrate, and motivate the study of higher strains.
{"title":"Modeling multiorbital effects in \u0000Sr2IrO4\u0000 under strain and a Zeeman field","authors":"L. Engström, T. Pereg-Barnea, W. Witczak-Krempa","doi":"10.1103/physrevb.103.155147","DOIUrl":"https://doi.org/10.1103/physrevb.103.155147","url":null,"abstract":"We present a comprehensive study of a three-orbital lattice model suitable for the layered iridate Sr2IrO4. Our analysis includes various on-site interactions (including Hubbard and Hund's) as well as compressive strain, and a Zeeman magnetic field. We use a self-consistent mean field approach with multiple order parameters to characterize the resulting phases. While in some parameter regimes the compound is well described by an effective J=1/2 model, in other regimes the full multiorbital description is needed. As a function of the compressive strain, we uncover two quantum phase transitions: first a continuous metal-insulator transition, and subsequently a first order magnetic melting of the antiferromagnetic order. Crucially, bands of both J=1/2 and J=3/2 nature play important roles in these transitions. Our results qualitatively agree with experiments of Sr2IrO4 under strain induced by a substrate, and motivate the study of higher strains.","PeriodicalId":8511,"journal":{"name":"arXiv: Strongly Correlated Electrons","volume":"4 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2020-12-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"78625839","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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