Motivated by numerical evidence of the valence bond groundstate of the two-dimensional Heisenberg pyrochlore lattice, we argue using a $t$-$J$ model that it evolves under doping into novel phases characterized by superconductivity coexisting with the underlying valence-bond solid order. A fermionic mean-field theory supplemented by exact diagonalization results provide strong arguments in favor of the stability of such supersolid phases. The resemblance with modulated superconducting patterns in high-$T_c$ cuprates as well as possible relevance to frustrated noncuprate superconductors such as spinels and pyrochlores is discussed.
The Heisenberg model on a face center cubic (fcc) lattice is a typical three-dimensional frustrated spin system expected to have magnetization plateaus and supersolid phases. There are model compounds $A_2$CoTeO$_6$ ($A$ = Ca, Sr, Pb) for the fcc lattice but with lattice distortions. Motivated by the presence of the compounds, we investigate the ground state of the spin-1/2 antiferromagnetic Heisenberg model on a tetragonally distorted fcc lattice in the magnetic field using a large-size cluster mean-field method for the sake of finding new supersolid phases. We find five supersolid phases in …
We examine instabilities of the plateau phases in the spin-1/2 kagome-lattice antiferromagnet in an applied field by means of degenerate perturbation theory, and find some emergent supersolid phases below the $m=5/9$ plateau. The wave functions of the plateau phases in a magnetic field have the particular construction based on the building blocks of resonating hexagons and their surrounding sites. Magnon excitations on each of these blocks suffer from a kinetic frustration effect, namely, they cannot hop easily to the others since the hopping amplitudes through the two paths destructively canc…
Prototypical models and their material incarnations are cornerstones to the understanding of quantum magnetism. Here we show theoretically that the recently synthesized magnetic compound Na$_2$BaCo(PO$_4$)$_2$ (NBCP) is a rare, nearly ideal material realization of the $S=1/2$ triangular-lattice antiferromagnet with significant easy-axis spin exchange anisotropy. By combining the automatic parameter searching and tensor-network simulations, we establish a microscopic model description of this material with realistic model parameters, which can not only fit well the experimental thermodynamic da…
Multilayered cuprates possess not only the highest superconducting temperature transition but also offer a unique platform to study disorder-free CuO$_2$ planes and the interplay between competing orders with superconductivity. Here, we study the underdoped trilayer cuprate HgBa$_2$Ca$_2$Cu$_3$O$_{8+ δ}$ and we report the first quantum oscillation and Hall effect measurements in magnetic field up to 88 T. A careful analysis of the complex spectra of quantum oscillations strongly supports the coexistence of an antiferromagnetic order in the inner plane and a charge order in the outer planes. Th…
Several material families show competition between superconductivity and other orders. When such competition is driven by doping, it invariably involves spatial inhomogeneities which can seed competing orders. We study impurity-induced charge order in the attractive Hubbard model, a prototypical model for competition between superconductivity and charge density wave order. We show that a single impurity induces a charge-ordered texture over a length scale set by the energy cost of the competing phase. Our results are consistent with a strong-coupling field theory proposed earlier in which supe…
Dissipationless dynamics of spin supersolid states in a spin-1/2 triangular antiferromagnet with impurities
RIKEN Center for Emergent Matter Science (CEMS)（理化学研究所物质结构理论研究中心）；School of Physics, Beihang University（北京航空航天大学物理学院）；Institute of Theoretical Physics, Chinese Academy of Sciences（中国科学院理论物理研究所）；Peng Huanwu Collaborative Center for Research and Education, Beihang University（北京航空航天大学彭桓武研究中心）；RIKEN Center for Computational Science (R-CCS)（理化学研究所计算科学中心）；RIKEN Center for Quantum Computing (RQC)（理化学研究所量子计算中心）；RIKEN Pioneering Research Institute (PRI)（理化学所先锋研究本部）；Advanced Science Research Center, Japan Atomic Energy Agency（日本原子力研究机构先进科学研究中心）
Nonmonotonic $d_{x^2-y^2}$ superconducting gap in electron-doped Pr$_{0.89}$LaCe$_{0.11}$CuO$_4$: Evidence of coexisting antiferromagnetism and superconductivity?
Dipolar and quadrupolar spin supersolid states in a spin-1 triangular antiferromagnet
RIKEN Center for Emergent Matter Science (CEMS)（理化学研究所物质结构研究センター）；Institute of Theoretical Physics, Chinese Academy of Sciences（中国科学院理论物理研究所）；RIKEN Center for Computational Science (R-CCS)（理化学研究所计算科学研究中心）；RIKEN Center for Quantum Computing (RQC)（理化学研究所量子计算研究中心）；RIKEN Pioneering Research Institute (PRI)（理化学研究所开创性研究所）；Advanced Science Research Center, Japan Atomic Energy Agency（日本原子力机构先进科学研究中心）
Transverse order and longitudinal fluctuations in a near-Ising spin supersolid
ETH Zürich（苏黎世联邦理工学院）；Université Grenoble Alpes, CEA, IRIG, MEM, MDN（格勒诺布尔阿尔卑斯大学）；J-PARC Center, Japan Atomic Energy Agency（日本原子力机构J-ARC中心）；Dresden High Magnetic Field Laboratory (HLD-EMFL) and Würzburg-Dresden Cluster of Excellence ctd.qmat, Helmholtz-Zentrum Dresden-Rossendorf（德累斯顿强磁场实验室和维尔茨堡-德累斯特卓越集群ctd.qmat，亥姆霍兹德累斯顿-罗斯多夫中心）；PSI Center for Neutron and Muon Sciences（保罗谢尔研究所中子与μ子科学中心）；Neutron Scattering Division, Oak Ridge National Laboratory（橡树岭国家实验室中子散射部）
Competing unconventional superconductivity and antiferromagnetism widely exist in several strongly correlated quantum materials whose direct simulation generally suffers from fermion sign problem. Here we report unbiased Quantum Monte Carlo (QMC) simulations on a sign-problem-free repulsive toy model with same onsite symmetries as the standard Hubbard model on a 2D square lattice. Using QMC, supplemented with mean-field and continuum field-theory arguments, we find that it hosts three distinct phases: a nodal d-wave phase, an antiferromagnet, and an intervening phase which hosts coexisting ant…
Spin supersolids and spin superfluids reveal complex canted spin structures with independent order of longitudinal and transverse spin components. This work addresses the question whether these exotic phases can exhibit spin-driven ferroelectricity. Here we report the results of dielectric and pyrocurrent measurements of MnCr2S4 as function of temperature and magnetic field up to 60 T. This sulfide chromium spinel exhibits a Yafet-Kittel type canted spin structure at low temperatures. As function of external magnetic field, the manganese spins undergo a sequence of ordering patterns of the tra…
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$_2$…
Understanding the microscopic mechanism of coexisting long-range orders (such as lattice supersolidity) in strongly correlated systems is a subject of immense interest. We study the possible manifestations of long-range orders, including lattice-supersolid phases with differently broken symmetry, in a two-dimensional square lattice system of hard-core bosons (HCBs) coupled to archetypal cooperative/coherent normal-mode distortions such as those in perovskites. At strong HCB-phonon coupling, using a duality transformation to map the strong-coupling problem to a weak-coupling one, we obtain an e…
We demonstrate that low-lying triplon excitations in a bilayer Heisenberg antiferromagnet provide a promising avenue to realize magnetic analogs of twisted superfluid and supersolid phases that were recently reported for two-component ultracold atomic condensate in an optical lattice. Using a cluster Gutzwiller mean-field theory, we establish that Dzyaloshinskii-Moriya interactions (DMI), that are common in many quantum magnets, stabilize these phases in a magnetic system, in contrast to the pair hopping process that is necessary for ultracold atoms. The critical value of DMI for transition to…
Topological magnons are emergent quantum spin excitations featured by magnon bands crossing linearly at the points dubbed nodes, analogous to fermions in topological electronic systems. Experimental realization of topological magnons in three dimensions has not been reported so far. Here, by measuring spin excitations (magnons) of a three-dimensional antiferromagnet Cu$_{3}$TeO$_{6}$ with inelastic neutron scattering, we provide direct spectroscopic evidence for the coexistence of symmetry-protected Dirac and triply degenerate nodes, the latter involving three-component magnons beyond the Dira…
Emergent Spin Supersolids in Frustrated Quantum Materials
RIKEN Center for Emergent Matter Science (CEMS)（理化学研究所新兴物质科学中心）；RIKEN Center for Computational Science (R-CCS)（理化学研究所计算科学中心）；RIKEN Center for Quantum Computing (RQC)（理化学研究所量子计算中心）；RIKEN Pioneering Research Institute (PRI)（理化学研究所先锋研究 institute）；Advanced Science Research Center, Japan Atomic Energy Agency（日本原子能机构先进科学研究中心）
RKKY-dipolar Interactions and 3D Spin Supersolid on Stacked Triangular Lattice
Institute of Theoretical Physics, Chinese Academy of Sciences（中国科学院理论物理研究所）；Hefei Institutes of Physical Science, Chinese Academy of Sciences（中国科学院合肥物质科学研究院）；University of Science and Technology of China（中国科学技术大学）；China Jiliang University（中国计量大学）；Shanghai Jiao Tong University（上海交通大学）；Nanjing University（南京大学）；Lanzhou University（兰州大学）
Double Supersolid Phase in a Bosonic t-J-V Model with Rydberg Atoms
Fudan University（复旦大学）；Shanghai Qizhi Institute and Shanghai Artificial Intelligence Laboratory（上海启智研究所与上海人工智能实验室）；Hefei National Laboratory（合肥国家实验室）；Westlake University（西湖大学）；Institute of Natural Sciences, Westlake Institute for Advanced Study（西湖高等研究院自然科学院）；Shanghai Research Center for Quantum Sciences（上海量子科学研究中心）
Angular Modulations in Magnetic Torque Induced by Phase Transitions in the Triangular Supersolid $2H$-AgNiO$_2$
University of Oxford（牛津大学）；Harvard John A. Paulson School of Engineering and Applied Sciences（哈佛大学约翰·A·保尔森工程与应用科学学院）；Florida State University（佛罗里达州立大学）；Max-Planck-Institut fur Festkörperforschung（马克斯·普朗克固体研究所）
The multi-orbital Hubbard model is investigated in order to clarify the electron correlation effects and the superconductivity in the iron-based superconductor. The renormalization effects on the self-energy and the two-particle irreducible vertex function are calculated on the basis of the dynamical mean field theory. We find that the vertex function exhibits a strong renormalization with the significant orbital dependence as compared with the renormalization factor, when the antiferromagnetic and the antiferro-orbital fluctuations are comparably enhanced due to the electron and the hole Ferm…
