Bulletin of the American Physical Society
APS March Meeting 2022
Volume 67, Number 3
Monday–Friday, March 14–18, 2022; Chicago
Session F64: Correlated Electron MagnetismRecordings Available
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Sponsoring Units: DCMP Chair: Trinanjan Datta, Augusta University Room: Hyatt Regency Hotel -Grant Park B |
Tuesday, March 15, 2022 8:00AM - 8:12AM |
F64.00001: Inverse Faraday effect in Mott insulators Saikat Banerjee, Umesh Kumar, Shizeng Lin The inverse Faraday effect (IFE), where a static magnetization is induced by circularly polarized light, offers a promising route to ultrafast control of spin states. Here we study the inverse Faraday effect in Mott insulators using the Floquet theory. In the Mott insulators with inversion symmetry, we find that the effective magnetic field induced by the IFE couples ferromagnetically to the neighboring spins. While for the Mott insulators without inversion symmetry, the effective magnetic field due to IFE couples antiferromagnetically to the neighboring spins. We apply the theory to the spin-orbit coupled single- and multi-orbital Hubbard model that is relevant for the Kitaev quantum spin liquid materials and demonstrate that the magnetic interactions can be tuned by light. |
Tuesday, March 15, 2022 8:12AM - 8:24AM |
F64.00002: Re-examination of the dependence of the 2 D liquid - Wigner crystal transition density on spin David M Ceperley Using new diffusion quantum Monte Carlo calculations, we estimate the density of the Wigner crystal transition for spinless fermions, spin 1/2 fermions, spin 3/2 fermions and for bosons in 2 dimensions. We also discuss the possible existence of a colloid phase regime at a density higher than the crystal phase. |
Tuesday, March 15, 2022 8:24AM - 8:36AM |
F64.00003: Direct observation of volume spin waves using quantum magnetometry Johannes Cremer, Shantam Ravan, Elizabeth Park, Ruolan Xue, Ronald L Walsworth, Amir Yacoby Spin waves can be used as signal carriers in electronics. Because of their low dissipation, spin waves can manipulate spin qubits with negligible heat losses compared to traditional microwave circuits. This has been recently demonstrated by coupling coherent spin waves in the magnetic insulator Yttrium Iron Garnet (YIG) to a single nitrogen vacancy center (NVs) in diamond. However, sensing using NV centers requires aligning the magnetic field to the NV axis at 54deg to the film which limits what type of spin waves can be detected at weak and strong magnetic fields. Here we demonstrate the use of diamond polished along the [111] axis, which allows magnetic field alignment perpendicular to the YIG film. This approach provides direct access to volume modes thereby extending the experimentally available parameter space . |
Tuesday, March 15, 2022 8:36AM - 8:48AM |
F64.00004: Thermodynamics of correlated electrons in a magnetic field Jixun K Ding, Wen O Wang, Brian Moritz, Yoni Schattner, Edwin Huang, Thomas P Devereaux We simulate the Hubbard-Hofstadter model using the numerically exact and unbiased determinant quantum Monte Carlo (DQMC) algorithm. We report the field and Hubbard interaction strength dependence of charge compressibility, fermion sign, local moment, magnetic structure factor, and specific heat. We find that some features of the non-interacting magnetic band structure are preserved in the presence of Hubbard repulsion and coexists with the Mott gap at half filling. We also find that incompressible regions of the phase diagram correspond to regions of improved fermion sign. At half filling, in the intermediate to strong coupling regime, we see that strong magnetic field delocalizes electrons and reduces the effect of Hubbard interaction on low-energy properties of the system. |
Tuesday, March 15, 2022 8:48AM - 9:00AM |
F64.00005: A Schwinger Boson Theory for the Magnetic Excitations of Ba3CoSb2O9 Esteban A Ghioldi, Shang-Shun Zhang, Yoshitomo Kamiya, Luis O Manuel, Adolfo E Trumper, Cristian Batista
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Tuesday, March 15, 2022 9:00AM - 9:12AM |
F64.00006: Unraveling higher-order corrections in the spin dynamics of RIXS spectra Umesh Kumar, Abhishek Nag, Jiemin Li, Hannah Robarts, Andrew Walters, Mirian Garcia-Fernandez, Romuald Saint-Martin, Alexander Revcolevschi, Justine Schlappa, Thorsten Schmitt, Steven S Johnston, Ke-Jin Zhou Resonant inelastic x-ray scattering (RIXS) is an evolving tool for investigating spin dynamics of strongly correlated materials, which complements inelastic neutron scattering. Both techniques have found that non-spin-conserving (NSC) excitations in quasi-1D isotropic quantum antiferromagnets are confined to the two-spinon phase space. Outside this phase space, only spin-conserving (SC) four-spinon excitations have been detected using O K-edge RIXS. Here, we investigate SrCuO2 and find four-spinon excitations outside the two-spinon phase space at both O K- and Cu L3-edges. Using the Kramers-Heisenberg formalism, we demonstrate that the four-spinon excitations arise from both SC and NSC processes at Cu L3-edge. We show that these new excitations only appear in the second-order terms of the ultra-fast core-hole lifetime expansion and arise from long-range spin fluctuations. These results thus open a new window to the spin dynamics of quantum magnets. |
Tuesday, March 15, 2022 9:12AM - 9:24AM |
F64.00007: Particle-hole asymmetry in the dynamical spin and charge responses of corner-shared 1D cuprates Shaozhi Li It has been debated for a long time whether the single-band Hubbard can describe the low-energy physics of the cuprate or not. This talk will present the results of the multi-orbital pd-model and the single-band Hubbard model for the corner-shared 1D cuprates. Here, we focus on the doping-dependent dynamical spin and charge structure factors, which can be measured in relevant experiments. We find many interesting results that cannot be captured by the single-band Hubbard model. For example, we find that the weight of the collective spin excitations between Cu and O orbitals is comparable to the weight of the spin excitations between two Cu orbitals. Importantly, we find a particle-hole asymmetry in the orbital-resolved charge excitations, which cannot be described by the single-band Hubbard model and is relevant to resonant inelastic X-ray scattering experiments. Our results imply that the explicit inclusion of the oxygen degrees of freedom may be required to understand experimental observations. |
Tuesday, March 15, 2022 9:24AM - 9:36AM |
F64.00008: Intra-excitonic spectroscopy of a Mott insulator Omar Mehio, Xinwei Li, Honglie Ning, Zala Lenarčič, Michael Buchhold, Zachary Porter, Nicholas J Laurita, Stephen Wilson, David Hsieh Excitons are traditionally studied in weakly interacting semiconductors where Coulombic binding is dominant, resulting in highly predictable, hydrogen-like states. However, far less is understood about excitons in strongly correlated electron systems, which exhibit complex interactions between charge, spin, orbital, and lattice degrees of freedom at energy scales relevant for excitonic binding. In this talk, I will discuss recent ultrafast time-resolved time-domain THz spectroscopy measurements directed at searching for signatures of intra-excitonic transitions in Mott antiferromagnets. Spectroscopic evidence of transient exciton formation will be compared against numerical calculations. |
Tuesday, March 15, 2022 9:36AM - 9:48AM |
F64.00009: Ultrafast optical excitation of magnetic dynamics in van der Waals magnets: Coherent magnons and BKT dynamics in NiPS3 Urban F Seifert, Mengxing Ye, Leon Balents Optical pumping of collective excitations in correlated electron systems and probing the subsequent response has received increased attention in past years for its ability to reveal intrinsic low energy dynamics of the system of interest. |
Tuesday, March 15, 2022 9:48AM - 10:00AM |
F64.00010: Lattice and magnetic dynamics in perovskite YVO3 Mott insulator investigated by neutron scattering Yu Tao, Douglas L Abernathy, Jiaqiang Yan, Tianran Chen, Taner Yildirim, Jianshi Zhou, John Goodenough, Despina A Louca The spin wave and phonon in YVO3 were investigated using powder inelastic neutron scattering. YVO3 is an antiferromagnetic Mott insulator with a TN = 118 K accompanied by a spin reorientation transition on warming from C-type to G-type at 77 K. This spin reorientation was observed from changes in the spin waves between 50 and 80 K. Using spinW, the magnetic exchange constants in the G- and C-type spin ordered structures are extracted to be Jab = Jc = -5.8 meV at 5 and 50 K, Jab = -3.8 meV, Jc = 7.6 meV at 80 K, Jab = -3.8 meV, Jc = 6.0 meV at 100 K. Below 118 K, paramagnetic scattering appears in the dynamic structure function S(Q,E). The phonon spectrum up to 130 meV as a function of temperature was also obtained and compared to first-principles calculations. Phonon intensity changes were observed between 50 and 80 K, mainly from the energy shifts of the optical Oxygen branches above 40 meV, linked to the orthorhombic to monoclinic structural transition on warming at 77 K. By comparison, little phonon change was observed across TN. |
Tuesday, March 15, 2022 10:00AM - 10:12AM |
F64.00011: Surrogate models for quantum spin systems based on reduced order modelling Stefan Wessel, Benjamin Stamm, Michael Herbst, Matteo Rizzi We present a methodology to investigate phase-diagrams of quantum spin models based on the principle of the reduced basis method. It is based on constructing a low-dimensional basis built from solutions of snapshots, i.e., ground states corresponding to particular and well-chosen parameter values. We propose to use a greedy-strategy to assemble the reduced basis and thus to select the parameter points where the full model is solved. Once the reduced basis is computed, observables required for the computation of phase-diagrams can be computed with a computational complexity independent of the underlying Hilbert space for any parameter value. We illustrate the accuracy of this approach for a geometrically frustrated antiferromagnetic two-dimensional lattice model and quantum spin model that describes a chain of excited Rydberg atoms. |
Tuesday, March 15, 2022 10:12AM - 10:24AM |
F64.00012: Hierarchical single-ion anisotropies in spin-1 Heisenberg antiferromagnets on the honeycomb lattice Nils Caci, Lukas Weber, Stefan Wessel We consider two-dimensional spin-1 antiferromagnets with distinct single-ion anisotropies along two perpendicular axes on the 2D honeycomb lattice. For a single easy-plane anisotropy, a Berezinskii-Kosterlitz-Thouless (BKT) transition is known to appear, below which quasi long-range order emerges. Instead, in the case of different anisotropies along two perpendicular axes, a thermal Ising transition with (true) long-range magnetic order appears. Recent inelastic neutron scattering experiments on the spin-1 compound BaNi${}_2$V${}_2$O${}_8$ indicate, however, that near to the critical point reminiscent BKT scaling still prevails. We investigate this scenario by addressing basic spin-1 models for BaNi${}_2$V${}_2$O${}_8$ with weak anisotropies, which we probe over the full range of experimentally relevant correlation length scales using large-scale quantum Monte Carlo simulations. |
Tuesday, March 15, 2022 10:24AM - 10:36AM |
F64.00013: Search for unusual orbital configuration and possible low-energy orbital excitations in CuSb2O6 1D magnet Carlos W Galdino, Thorsten Schmitt, Tulio C Rocha, Thiago Mori, Eduardo Granado, John J Neumeier Low-dimensional cuprates display a variety of exotic physical properties. They tend to exhibit either a quasiplanar CuO4 coordination or CuO6 octahedra that are highly distorted due to the Jahn-Teller effect, leading to a large (>1 eV) energy separation between the x2−y2 and 3z2−r2 -like orbital states for the Cu2+ 3d hole. In contrast, the quasi-1D magnet Mott insulator CuSb2O6 shows fairly regular CuO6 octahedra that seem to promote a close competition between the 3z2−r2 and x2−y2 levels. In fact, Ab-initio band structure calculations predict a separation of only ~0.3 eV between these levels [1]. X-ray absorption spectroscopy experiments indicate small anisotropy between different geometries of incident light, which supports the idea of a strong competition between x2−y2 and 3z2−r2 orbitals in the ground state. Two possibilities are considered: 1) the ground state is a combination of these two electronic states or 2) the orbital ordering is well defined even though the dichroic signal is negligible due to a small energy splitting between the two eg levels. In addition, the small energy separation between eg levels may lead to new pathways for electron-phonon interaction in this cuprate. Indeed, a recent report from our group displays Raman spectroscopy data that support this general idea, identifying an electronic excitation that strongly interacts with phonons and may be ascribed to an orbiton [2]. In this work, we will show and discuss resonant inelastic X-ray scattering (RIXS) experiments that shed light on this possible unusual ground state, the presumably small Cu eg orbital splitting, and the possible existence of orbitons in this unusual 1D magnetic cuprate with trirutile structure. |
Tuesday, March 15, 2022 10:36AM - 10:48AM |
F64.00014: First Principles theory of carrier doping of prototype Mott insulators MnO and NiO—polaron trapping vs. band conductivity Hannes Raebiger, Soungmin Bae, Zhi Wang, Oleksandr I Malyi, Alex Zunger We investigate theoretically the microscopic mechanisms of carrier doping in the paradigmatic antiferromagnetic (AFM) and paramagnetic (PM) phases of MnO and NiO by first principles supercell calculation allowing symmetry breaking. To correctly describe strong correlation effects, we extend density-functional theory to comply with Koopmans’ linearity. Transitions are described by relaxed total energy differences, not orbital energies. For NiO, we find delocalized perturbed host band states for both electron and hole doping, in both AFM and PM phases, including a split-off small polaron like state just 0.1 eV above the ground state, in agreement with observations. For MnO, we find a clear asymmetry between electron and hole doping: holes get trapped in split-off deep gap states, whereas electrons are delocalized in conduction band states. For the split-off small polaron states in both MnO and NiO, the charge trapping changes the on-site screening, which via a charge self-regulation mechanism not only induces new gap states akin to Zhang-Rice states, but also induces ultra-deep states that lie below the valence band. |
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