当载流子加入到反铁磁有序的CuO 2层中时，层状氧化铜化合物中出现了超导电性。载流子破坏了反铁磁秩序，但强烈的自旋涨落在整个超导阶段持续存在，并与超导性密切相关。在空穴掺杂的铜氧化物自旋波动的中子散射测量揭示了一个不寻常的'沙漏'功能的动量分辨的磁谱，目前在广泛的超导和非超导材料。对于这一特性，目前还没有被广泛接受的解释。一种可能性是，它来自于交替的自旋和电荷条纹的图案，这一想法得到了对条纹有序的La 1.875 Ba 0.125 CuO 4的测量的支持。然而，许多没有条纹顺序的氧化铜也表现出沙漏光谱。在这里，我们报告的观察沙漏磁谱的空穴掺杂的反铁磁体从家庭以外的超导铜氧化物。我们的系统具有条纹相关性，并且是绝缘体，这意味着它的磁动力学可以最终归因于条纹。这些结果提供了令人信服的证据，证明氧化铜超导体中的沙漏光谱是由波动条纹引起的。
英文摘要：
Superconductivity in layered copper-oxide compounds emerges when charge carriers are added to antiferromagnetically-ordered CuO2 layers. The carriers destroy the antiferromagnetic order, but strong spin fluctuations persist throughout the superconducting phase and are intimately linked to super-conductivity. Neutron scattering measurements of spin fluctuations in hole-doped copper oxides have revealed an unusual `hour-glass' feature in the momentum-resolved magnetic spectrum, present in a wide range of superconducting and non-superconducting materials. There is no widely-accepted explanation for this feature. One possibility is that it derives from a pattern of alternating spin and charge stripes, an idea supported by measurements on stripe-ordered La1.875Ba0.125CuO4. However, many copper oxides without stripe order also exhibit an hour-glass spectrum$. Here we report the observation of an hour-glass magnetic spectrum in a hole-doped antiferromagnet from outside the family of superconducting copper oxides. Our system has stripe correlations and is an insulator, which means its magnetic dynamics can conclusively be ascribed to stripes. The results provide compelling evidence that the hour-glass spectrum in the copper-oxide superconductors arises from fluctuating stripes.
In contrast to the "Pr-issue" that neither PrBa2Cu3O7 (Pr123) nor PrBa2Cu4O8 (Pr124) shows superconductivity (SC), we have observed 100%-fraction of SC in an oxygen-reduced Pr2Ba4Cu7O(15-delta) (Pr247) which has a hybrid structure that Pr247 = Pr123 + Pr124. It is found that Cu nuclear-spin signals from the CuO2 planes observed at 300K are completely wiped out down at 2K. Instead, plane signals at 2K are observed at higher frequencies. This indicates that, despite the bulk SC, the CuO2 planes in Pr247 are found to be in an insulating and antiferromagnetically ordered state.
We present a comprehensive study of strain-induced topological magnon phase transitions in insulating three-dimensional (3D) topological chiral antiferromagnets on the kagome-lattice. We show that by applying (100) uniaxial strain, 3D insulating antiferromagnetic Weyl magnons (WMs) manifest as an intermediate phase between a strain-induced 3D magnon Chern insulator (MCI) with integer Chern numbers and a 3D trivial magnon insulator with zero Chern number. In addition, we show that strain suppresses the topological thermal Hall conductivity of magnons in these systems. Due to the similarity betw…
Magnetic correlations and quantum criticality in the insulating antiferromagnetic, insulating spin liquid, renormalized Fermi liquid, and metallic antiferromagnetic phases of the Mott system V_2O_3
How superconductivity emerges in the vicinity of an antiferromagnetic insulating state is a long-standing issue of strong correlation physics. We study the transition from an antiferromagnetic insulator to a superconductor by hole-doping based on a bilayer generalization of a Hubbard-like model. The projector quantum Monte-Carlo simulations are employed, which are sign-problem-free both at and away from half-filling. An anisotropic Ising antiferromagnetic Mott insulating phase occurs at half-filling, which is weakened by hole-doping. Below a critical doping value, antiferromagnetism coexists w…
By the example of Heisenberg $d$-dimensional disordered non-frustrated antiferromagnets, we discuss quantum transitions at $d\ge2$ from magnetically ordered (superfluid) to various disorder-induced insulating phases (Bose-glass, Mott-glass, etc.) in Bose systems with quenched disorder. We perform a scaling consideration as well as a discussion based on the hydrodynamic description of long-wavelength excitations and on the assumption that the ordered part of the system shows fractal properties near the transition point. We propose that the scaling ansatz for the singular part of the free energy…
Conversion of glassy antiferromagnetic-insulating phase to equilibrium ferromagnetic-metallic phase by devitrification and recrystallization in Al substituted Pr${_{0.5}}$Ca$_{0.5}$MnO${_3}$
结果表明，Pr ${_{0.5}}$ Ca $_{0.5}$ MnO ${_3}$和La ${_{0.5}}$ Ca $_{0.5}$ MnO ${_3}$（LCMO）在低温下表现出定性相似且明显异常的M-H曲线。在磁场作用下，两种材料都发生了一个宽的一阶不可逆的反铁磁（AF）-绝缘（I）-铁磁（FM）-金属（M）相变，并产生了软FM态。而Pr $_{0.5}$ Ca $_{0.5}$ Mn $_{0.975}$ Al $_{0.025}$ O $_3$（PCMAO）的低温平衡态为FM-M，而LCMO的低温平衡态为AF-I。在这两个系统中，各自的平衡相共存的另一个阶段与相反的顺序，这是不平衡的，和冷却场可以调整的分数共存相。它表明较早的共存FM-M相的行为像“磁性玻璃”在LCMO。在这里，我们表明，从专门设计的测量协议的AF-I相的PCMAO具有磁性玻璃态的所有特征。它在加热时失透，并且在退火后再结晶为平衡FM-M相。这种玻璃状的AF-I相也显示出类似的有趣的功能，观察到在FM-M磁性玻璃态的LCMO，当开始共存的玻璃分数较大，连续退火的结果在较大的平衡相的分数。两个锰氧化物系统之间的这种相似性，与各自的玻璃相和平衡相的对比磁顺序指向一个可能的普遍性。
The theory behind the electrical switching of antiferromagnets is premised on the existence of a well defined broken symmetry state that can be rotated to encode information. A spin glass is in many ways the antithesis of this state, characterized by an ergodic landscape of nearly degenerate magnetic configurations, choosing to freeze into a distribution of these in a manner that is seemingly bereft of information. In this study, we show that the coexistence of spin glass and antiferromagnetic order allows a novel mechanism to facilitate the switching of the antiferromagnet Fe$_{1/3+δ}$NbS$_2$…
We describe square lattice spin liquids which break time-reversal symmetry, while preserving translational symmetry. The states are distinguished by the manner in which they transform under mirror symmetries. All the states have non-zero scalar spin chirality, which implies the appearance of spontaneous orbital charge currents in the bulk (even in the insulator); but in some cases, orbital currents are non-zero only in a formulation with three orbitals per unit cell. The states are formulated using both the bosonic and fermionic spinon approaches. We describe states with $\mathbb{Z}_2$ and U(1…
The quantum kagome antiferromagnets YCu3(OH)6OxCl3-x (x=0,1/3) are produced using a unified solid state synthesis route for polycrystalline samples. From structural refinements based on neutron diffraction data, we clarify the structure of the Y3Cu9(OH)18OCl8 (x=1/3) compound and provide a revised chemical formula. We use muon spin relaxation, as a local probe of magnetism, to investigate the exotic low temperature properties in the two compounds. In agreement with the low temperature neutron diffraction data, we find no evidence for long range ordering in both materials but they exhibit disti…
Here we investigate antiferromagnetic Eu$_{5}$In$_{2}$Sb$_{6}$, a nonsymmorphic Zintl phase. Our electrical transport data show that Eu$_{5}$In$_{2}$Sb$_{6}$ is remarkably insulating and exhibits an exceptionally large negative magnetoresistance, which is consistent with the presence of magnetic polarons. From {\it ab initio} calculations, the paramagnetic state of Eu$_{5}$In$_{2}$Sb$_{6}$ is a topologically nontrivial semimetal within the generalized gradient approximation (GGA), whereas an insulating state with trivial topological indices is obtained using a modified Becke-Johnson potential.…
Antiferromagnetic stripe phase and large-gap insulating ground state of the correlated $\sqrt{3}\times\sqrt{3}$~R30$^{\circ}$-Sn/Si(111) single atomic layer
Sorbonne Université, CNRS, Institut des Nanosciences de Paris（索邦大学，法国国家科学研究中心，巴黎纳米科学研究所）；Department of Physical and Chemical Sciences, University of L’Aquila（拉奎拉大学物理与化学科学系）；CNR-SPIN c/o Department of Physical and Chemical Sciences, University of L’Aquila（意大利国家研究委员会自旋物理中心（挂靠拉奎拉大学物理与化学科学系））；Institut de Minéralogie, de Physique des Matériaux et de Cosmochimie (IMPMC), Sorbonne Université, CNRS UMR 7590, MNH（矿物学、材料物理与宇宙化学研究所（IMPMC），索邦大学，法国国家科学研究中心UMR 7590，自然历史博物馆）
We use a non-equilibrium many-body theory that engages the elements of transient coherence, correlation, and nonlinearity to describe changes in the magnetic and electronic phases of strongly correlated systems induced by femtosecond nonlinear photoexcitation. Using a generalized tight--binding mean field approach based on Hubbard operators and including the coupling of the laser field, we describe a mechanism for simultaneous insulator--to--metal and anti-- to ferro--magnetic transition to a transient state triggered by non-thermal ultrafast spin and charge coupled excitations. We demontrate,…
Quantum criticality is a fundamental organizing principle for studying strongly correlated systems. Nevertheless, understanding quantum critical dynamics at nonzero temperatures is a major challenge of condensed matter physics due to the intricate interplay between quantum and thermal fluctuations. The recent experiments in the quantum spin dimer material TlCuCl$_3$ provide an unprecedented opportunity to test the theories of quantum criticality. We investigate the nonzero temperature quantum critical spin dynamics by employing an effective $O(N)$ field theory. The on-shell mass and the dampin…
We study effects of quenched bond disorder in frustrated easy-plane antiferromagnets in two space dimensions, using a combination of analytical and numerical techniques. We consider local-moment systems which display non-collinear long-range order at zero temperature, with the antiferromagnetic triangular-lattice XY model as a prime example. We show that (i) weak bond disorder transforms the clean ground state into a state with quasi-long-range order, and (ii) strong bond disorder results in a short-range-ordered glassy ground state. Using extensive Monte Carlo simulations, we also track the f…
We theoretically show that the Kitaev interaction generates a novel class of spin texture in the excitation spectrum of the antiferromagnetic insulator found in the Kitaev-Heisenberg-$Γ$ model. In conducting electronic systems, there is a series of vortex type of spin texture along the Fermi surface induced by Rashba and Dresselhaus spin-orbit coupling. Such spin textures are rarely found in magnetic insulators, since there had been no systematic ways to control the kinetics of its quasi-particle called magnon using a magnetic field or spacially asymmetric exchange couplings. Here, we propose …
We study the impact of quenched disorder (random exchange couplings or site dilution) on easy-plane pyrochlore antiferromagnets. In the clean system, order-by-disorder selects a magnetically ordered state from a classically degenerate manifold. In the presence of randomness, however, different orders can be chosen locally depending on details of the disorder configuration. Using a combination of analytical considerations and classical Monte-Carlo simulations, we argue that any long-range-ordered magnetic state is destroyed beyond a critical level of randomness where the system breaks into magn…
Tailoring transport properties of strongly correlated electron systems in a controlled fashion counts among the dreams of materials scientists. In copper oxides, varying the carrier concentration is a tool to obtain high-temperature superconducting phases. In manganites, doping results in exotic physics such as insulator-metal transitions (IMT), colossal magnetoresistance (CMR), orbital- or charge-ordered (CO) or charge-disproportionate (CD) states. In most oxides, antiferromagnetic order and charge-disproportionation are asssociated with insulating behavior. Here we report the realization of …
