Successive magnetic transitions relating to itinerant spins and localized Cu spins in La2-xSrxCu1-yFeyO4: Possible existence of stripe correlations in the overdoped regime
为了研究所谓的条纹关联与高温超导性之间的关系，我们对部分Fe取代的La 2-xSrxCu 1-yFeyO 4（LSCFO）进行了磁化率和零场μ子自旋弛豫测量.已经发现，Fe替代诱导连续的磁过渡在过掺杂制度，即，由于RKKY相互作用的基础上巡回自旋在较高的温度和条纹顺序过渡的本地化的Cu 2+自旋在较低的温度下的Fe 3+自旋的自旋玻璃化转变。条纹顺序过渡消失的空穴浓度约0.28每铜，这与在原始的La 2-xSrxCuO 4的超导性的终点相吻合，表明条纹的相关性是密切相关的高Tc超导电性在过掺杂制度，以及在欠掺杂制度。对于自旋玻璃态，我们发现极化巡游自旋对μ子自旋去极化的贡献是不可忽略的。考虑到R.- H. He等人[Phys. Rev. Lett. 107，127002（2011）]，已经在过掺杂的LSCFO中观察到自旋密度波（SDW）序，本结果证明了SDW序和自旋玻璃态的新共存态的存在。
英文摘要：
In order to investigate the relationship between the so-called stripe correlations and the high-Tc superconductivity, we have carried out magnetic susceptibility and zero-field muon-spin-relaxation measurements in partially Fe-substituted La2-xSrxCu1-yFeyO4 (LSCFO). It has been found that the Fe substitution induces successive magnetic transitions in the overdoped regime, namely, a spin-glass transition of Fe3+ spins due to the RKKY interaction based on itinerant spins at higher temperatures and a stripe-order transition of localized Cu2+ spins at lower temperatures. The stripe-order transition disappears at the hole concentration of ~0.28 per Cu which coincides with the endpoint of the superconductivity in pristine La2-xSrxCuO4, suggesting that the stripe correlations are closely related to the high-Tc superconductivity in the overdoped regime as well as in the underdoped regime. As for the spin-glass state, it has been found that the contribution of polarized itinerant spins to the muon-spin depolarization is not negligible. Taking into account neutron-scattering results by R.-H. He et al. [Phys. Rev. Lett. 107, 127002 (2011)] that a spin-density-wave (SDW) order has been observed in overdoped LSCFO, the present results demonstrate the presence of a novel coexistent state of a SDW order and a spin-glass state.
Hidden itinerant-spin phase in heavily-overdoped La2-xSrxCuO4 revealed by dilute Fe doping: A combined neutron scattering and angle-resolved photoemission study
We investigate Cu-doped Ba(Fe$_{1-x}$Cu$_x$)$_2$As$_2$ with transport, magnetic susceptibility, and elastic neutron scattering measurements. In the heavily Cu-doped regime where long-range stripe-type antiferromagnetic order in BaFe$_2$As$_2$ is suppressed, Ba(Fe$_{1-x}$Cu$_x$)$_2$As$_2$ (0.145 $\leq x \leq$ 0.553) samples exhibit spin-glass-like behavior in magnetic susceptibility and insulating-like temperature dependence in electrical transport. Using elastic neutron scattering, we find stripe-type short-range magnetic order in the spin-glass region identified by susceptibility measurements…
Understanding the overall features of magnetic excitation is essential for clarifying the mechanism of Cooper pair formation in iron-based superconductors. In particular, clarifying the relationship between magnetism and superconductivity is a central challenge because magnetism may play a key role in their exotic superconductivity. BaFe2As2 is one of ideal systems for such investigation because its superconductivity can be induced in several ways, allowing a comparative examination. Here we report a study on the spin fluctuations of the hole-overdoped iron-based superconductors Ba1-xKxFe2As2 …
We report a study of the Ca$_{0.73}$La$_{0.27}$FeAs$_2$ single crystals. We unravel a monoclinic to triclinic phase transition at 58 K, and a paramagnetic to stripe antiferromagnetic (AFM) phase transition at 54 K, below which spins order 45$^\circ$ away from the stripe direction. Furthermore, we demonstrate this material is substantially structurally untwinned at ambient pressure with the formation of spin rotation walls (S-walls). Finally, in addition to the central-hole and corner-electron Fermi pockets usually appearing in Fe pnictide superconductors, angle-resolved photoemission (ARPES) m…
We demonstrate the presence of ferromagnetic (FM) fluctuations in the superconducting and non-superconducting heavily overdoped regimes of high-temperature superconducting copper oxides, using (Bi,Pb)_2_Sr_2_CuO_6+delta_ (Bi-2201) single crystals. Magnetization curves exhibit a tendency to be saturated in high magnetic fields at low temperatures in the heavily overdoped crystals, which is probably a precursor phenomenon of a FM transition at a lower temperature. Muon spin relaxation detects the enhancement of spin fluctuations at high temperatures below 200 K. Correspondingly, the ab-plane res…
Commensurate Itinerant Antiferromagnetism in BaFe2As2: 75As-NMR Studies on a Self-Flux Grown Single Crystal
我们报告的结果75砷核磁共振（NMR）实验上的自助熔剂生长的BaFe 2 As 2单晶。一个一级反铁磁（AF）转变附近135 K的NMR谱线的分裂，这是伴随着同时的结构转变，证明了突然大的变化的电场梯度张量在作为网站。NMR结果导致几乎唯一的条纹自旋结构在AF相。自旋-晶格弛豫速率的数据表明，在顺磁相中，随着温度的降低，各向异性的条纹型自旋涨落的发展。
We present a resonant inelastic x-ray scattering (RIXS) study of spin and charge excitations in overdoped La1.77Sr0.23CuO4 along two high-symmetry directions. The line shape of these excitations is analyzed and they are shown to be highly overdamped. Their spectral weight and damping are found to be strongly momentum dependent. Qualitative agreement between these observations and a calculated RPA susceptibility is obtained for this overdoped compound, implying that a significant contribution to the RIXS signal stems from a continuum of charge excitations. Furthermore, this suggests that the sp…
Spin canting as a result of the competition between stripes and spirals in cuprates
在推广的哈伯德模型的基础上，我们计算了条形和螺旋形基态的能量。我们发现，均匀的螺旋得到青睐的一个大的$t'/t$比，但不稳定，在小掺杂对条纹和棋盘纹理与自旋倾斜。这些不均匀性的结构也取决于t '/t，并且相关联的自旋电流可以引起与局部偶极矩相关联的小的晶格畸变。本文讨论了一种新的条纹，它是反铁磁（AF）序参量畴壁，且AF序的相位发生分数变化。大型|t'/t|在某些条件下，在过掺杂的制度，这可以解释最近在铁共掺杂的Bi 22 O 1材料中观察到的弹性无公度磁响应的螺旋可以稳定。
Interplay between tetragonal magnetic order, stripe magnetism, and superconductivity in iron-based materials
受Ba $_{1-x}$ K $_{x}$ Fe $_{2}$ As $_{2}$ {[} A. e. Böhmer \textit{et al}，待发表{]}，我们分析了掺杂铁磷属元素化物中自旋密度波（SDW）有序的类型和超导转变温度$T_{c}$在与SDW磁性共存相中的不连续性。通过跟踪磁跃迁线$T_{N}(x)$走向最佳掺杂的巡回费米子模型，我们发现了一个序列的过渡从条纹正交（$C_{2}$）SDW秩序的四（$C_{4}$）秩序，然后回到$C_{2}$秩序。我们认为，超导$T_{c}$有两个不连续性-它跳到一个较小的值时，进入共存区的$C_{4}$磁相，然后跳到一个较大的值内的SDW状态时，它越过之间的边界$C_{4}$和$C_{2}$ SDW订单。与实验相图的完全协议提供了一个强有力的指示，巡回的方法是足够的弱/中度掺杂的铁磷属元素化物的物理描述。
The cuprate high-temperature superconductors (HTSC) have been the subject of intense study for more than 30 years with no consensus yet on the underlying mechanism of the superconductivity. Conventional wisdom dictates that the mysterious and extraordinary properties of the cuprates arise from doping a strongly correlated antiferromagnetic (AFM) insulator (1,2). The highly overdoped cuprates$-$those beyond the dome of superconductivity (SC)--are considered to be conventional Fermi liquid metals (3). Here, we report the emergence of itinerant ferromagnetic order (FM) below 4K for doping beyond …
Using muon spin rotation and infrared spectroscopy we study the relation between magnetism and superconductivity in Ba$ _{1-x} $K$ _{x} $Fe$ _{2} $As$ _{2} $ single crystals from the underdoped to the slightly overdoped regime. We find that the Fe magnetic moment is only moderately suppressed in most of the underdoped region where it decreases more slowly than the Néel-temperature, $ T^{\mathrm{N}} $. This applies for both the total Fe moment obtained from muon spin rotation and for the itinerant component that is deduced from the spectral weight of the spin-density-wave pair breaking peak in …
Coexistence of localized and itinerant magnetism in newly discovered iron-selenide superconductor LiFeO2Fe2Se2
采用第一性原理方法研究了LiFeO $_{2}$ Fe $_{2}$ Se $_{2}$的电子结构和磁性.在LiFeO $_{2}$层中，Fe 1的基态为N $\acute{e}$ el反铁磁（AFM）Mott绝缘态，具有局域磁性;在Fe $_{2}$ Se $_{2}$层中，Fe 2的基态为条纹状AFM金属态，具有巡游磁性;此外，层状LiFeO $_{2}$被发现是超过一个绝缘块层，但负责增强AFM相关的Fe $_{2}$ Se $_{2}$层通过层间磁耦合。Fe 1和Fe 2的磁性之间的相互作用引入了与铁基超导体中的超导性相关的自旋涨落的控制机制。
Electronic charge order is a symmetry breaking state in high-$T_\mathrm{c}$ cuprate superconductors. In scanning tunneling microscopy, the detected charge-order-induced modulation is an electronic response of the charge order. For an overdoped (Bi,Pb)$_2$Sr$_2$CuO$_{6+x}$ sample, we apply scanning tunneling microscopy to explore local properties of the charge order. The ordering wavevector is non-dispersive with energy, which can be confirmed and determined. By extracting its order-parameter field, we identify dislocations in the stripe structure of the electronic modulation, which correspond …
Trilayer nickelates, which exhibit a high degree of orbital polarization combined with an electron count (d8.67) corresponding to overdoped cuprates, have been identified as a promising candidate platform for achieving high-Tc superconductivity. One such material, La4Ni3O8, undergoes a semiconductor-insulator transition at ~105 K, which was recently shown to arise from the formation of charge stripes. However, an outstanding issue has been the origin of an anomaly in the magnetic susceptibility at the transition and whether it signifies formation of spin stripes akin to single layer nickelates…
Spin Waves and Spatially Anisotropic Exchange Interactions in the $\mathrm{S=2}$ Stripe Antiferromagnet Rb$_{0.8}$Fe$_{1.5}$S$_2$
用中子非弹性散射方法研究了绝缘Rb $_{0.8}$ Fe $_{1.5}$ S $_2$在布里渊区的条纹反铁磁序自旋波。自旋波谱很好地描述了海森堡哈密顿与各向异性的面内交换相互作用。对有序矩和自旋涨落进行积分，得到$27.6\pm4.2μ_B^2$ /Fe的总矩平方，与$\mathrm{S \approx 2}$一致。不同于$X$ Fe $_2$ As $_2$（$X=$ Ca，Sr和Ba），其中巡回电子有显着的贡献，我们的数据表明，Rb $_{0.8}$ Fe $_{1.5}$ S $_2$中的这种条纹反铁磁有序相是一个莫特状绝缘体，具有完全本地化的$3d$电子和高自旋基态配置。然而，各向异性交换耦合似乎是普遍的，在条纹相的铁磷属化物和硫属化物。
We elucidate the pivotal role of the bandstructure's orbital content in deciding the type of commensurate magnetic order stabilized within the itinerant scenario of iron-pnictides. Recent experimental findings in the tetragonal magnetic phase attest to the existence of the so-called charge and spin ordered density wave over the spin-vortex crystal phase, the latter of which tends to be favored in simplified band models of itinerant magnetism. Here we show that employing a multiorbital itinerant Landau approach based on realistic bandstructures can account for the experimentally observed magnet…
The electronic structure and magnetism of a new magnetic intercalation compound (Li0.8Fe0.2)OHFeSe are investigated theoretically. The electronic structure calculations predict that the Fe in the (Li,Fe)OH intercalated layer is in +2 valence state, i.e. there is electron doping to the FeSe layer, resulting in the shrinking of the Fermi surface (FS) pocket around Gamma and a strong suppression of dynamical spin susceptibility at M in comparison with the bulk FeSe compound. The ground state of the FeSe layer is a striped antiferromagnetic (SAFM) metal, while the (Li,Fe)OH layer displays a very w…
Cu Nuclear Quadrupole Resonance Study of La_{2-x}Sr_xCu_{1-y}Zn_yO_4 (x=0.10, 0.15 and 0.20): Zn-induced Wipeout Effect near the Magnetic and Electric Instability
We use neutron scattering to study vanadium (hole)-doped LiFe$_{1-x}$V$_x$As. In the undoped state, LiFeAs exhibits superconductivity at $T_c=18$ K and transverse incommensurate spin excitations similar to electron overdoped iron pnictides. Upon vanadium-doping to form LiFe$_{0.955}$V$_{0.045}$, the transverse incommensurate spin excitations in LiFeAs transform into longitudinally elongated in a similar fashion as that of potassium (hole) doped Ba$_{0.7}$K$_{0.3}$Fe$_2$As$_2$, but with dramatically enhanced magnetic scattering and elimination of superconductivity. This is different from the su…
Effects of Zn and Ni substitution on the Cu-spin dynamics and superconductivity in La_2-x_Sr_x_Cu_1-y_(Zn,Ni)_y_O_4_ with x=0.15-0.20 studied by the muon spin relaxation and magnetic susceptibility
Magnetic field effect on Fe-induced short-range magnetic correlation and electrical conductivity in Bi$_{1.75}$Pb$_{0.35}$Sr$_{1.90}$Cu$_{0.91}$Fe$_{0.09}$O$_{6+y}$
我们报告的电阻率测量和磁场下的中子衍射研究Bi $_{1.75}$ Pb $_{0.35}$ Sr $_{1.90}$ Cu $_{0.91}$ Fe $_{0.09}$ O $_{6+y}$，其中空穴载流子过掺杂。该化合物显示出短程无公度磁相关，具有不可分辨性$δ=0.21$，而不含Fe的化合物没有显示出磁相关。电阻率在低温下以$ln(1/T)$的形式上升，不显示超导性。我们观察到通过施加磁场（即，负磁阻效应）。磁场的施加也抑制了Fe诱导的无公度磁关联。我们比较和对比这些观察与两种不同的模型：1）条纹顺序，和2）在金属合金中的稀释磁矩，与相关的近藤行为。后一种情况似乎与目前的结果更相关。
Magnetic configurations and excitations in high-$T_{c}$ multilayer nickelates
Beijing National Laboratory for Condensed Matter Physics and Institute of Physics, Chinese Academy of Sciences（中国科学院物理研究所，凝聚态物理北京国家实验室）；School of Physical Sciences, University of Chinese Academy of Sciences（中国科学院大学物理科学学院）；Institute of Theoretical Physics, Chinese Academy of Sciences（中国科学院理论物理研究所）；New Cornerstone Science Laboratory, Institute of Physics, Chinese Academy of Sciences（中国科学院物理研究所，新基石科学实验室）
Crossover from spin-waves to diffusive spin excitations in underdoped Ba(Fe$_{1-x}$Co$_{x}$)$_{2}$As$_{2}$
利用非弹性中子散射，我们表明，在欠掺杂的Ba（Fe $_{1-x}$ Co $_{x}$）$_{2}$ As $_{2}$的超导性的开始符合从定义明确的自旋波的交叉过阻尼和扩散的自旋激发。这种交叉发生，尽管存在的长程条纹反铁磁顺序的样品在一个组成范围从x=0.04-0.055，是一个结果的收缩自旋密度波隙和相应的增加的粒子孔（朗道）阻尼。后者的效果被捕获由一个简单的巡回模型有关的Co掺杂的费米表面的热点的变化。我们认为，过阻尼自旋涨落提供了一个配对机制，在这些材料的超导性。
In most magnetically-ordered iron pnictides, the magnetic moments lie in the FeAs planes, parallel to the modulation direction of the spin stripes. However, recent experiments in hole-doped iron pnictides have observed a reorientation of the magnetic moments from in-plane to out-of-plane. Interestingly, this reorientation is accompanied by a change in the magnetic ground state from a stripe antiferromagnet to a tetragonal non-uniform magnetic configuration. Motivated by these recent observations, here we investigate the origin of the spin anisotropy in iron pnictides using an itinerant microsc…
We investigate the re-entrant tetragonal phase in the iron-based superconductor Ba0 .76K0.24Fe2As2 by DC magnetization and thermoelectrical measurements. The reversible magnetization confirms by a thermodynamic method that the spin alignment in the re-entrant C4 phase is out-of-plane, in agreement with an itinerant double-Q magnetic order [Allred et al., Nat. Phys. 12, 493 (2016)]. The Nernst coefficient shows the typical unusually large negative value in the stripe-type spin density wave (SDW) state owing to the Fermi surface reconstruction associated with SDW and nematic order. At the transi…
We use time-of-flight (ToF) inelastic neutron scattering (INS) spectroscopy to investigate the doping dependence of magnetic excitations across the phase diagram of NaFe$_{1-x}$Co$_x$As with $x=0, 0.0175, 0.0215, 0.05,$ and $0.11$. The effect of electron-doping by partially substituting Fe by Co is to form resonances that couple with superconductivity, broaden and suppress low energy ($E\le 80$ meV) spin excitations compared with spin waves in undoped NaFeAs. However, high energy ($E> 80$ meV) spin excitations are weakly Co-doping dependent. Integration of the local spin dynamic susceptibility…
Low Energy, Coherent, Stoner-like Excitations in CaFe$_{2}$As$_{2}$
利用线性响应密度泛函理论，研究了CaFe $_{2}$ As $_{2}$条纹相的磁激发随局域磁矩振幅的变化.我们发现了一种新的激发：在能量与N{é}el温度相当的Stoner类（巡回）激发的尖锐共振，主要来自费米能级附近的Fe $d$态的窄带，并与更传统的（局域化）自旋波共存。这两种激发都可以显示出多个分支，突出了基于局域自旋模型的描述的不足。
