Bulletin of the American Physical Society
APS March Meeting 2021
Volume 66, Number 1
Monday–Friday, March 15–19, 2021; Virtual; Time Zone: Central Daylight Time, USA
Session Y39: Kagome & Triangular Systems IIFocus Live
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Sponsoring Units: GMAG DMP Chair: Cristian Batista, University of Tennessee |
Friday, March 19, 2021 11:30AM - 11:42AM Live |
Y39.00001: Effects of exchange distortions and spin rotation on the spin dynamics of the magnetic Kagome lattice Abigail Coker, Avadh Saxena, Jason Haraldsen In this talk, we examine the effect of distorted magnetic interactions in the Kagome lattice on the spin-wave dynamics. Using a Holstein-Primakoff expansion of the Heisenberg Hamiltonian, we determine the analytical solutions for the various magnetic configurations on the Kagome lattice. Through an understanding of the magnetic phase diagram, we characterize the changes in the spin-waves of the standard magnetic configurations with variable exchange interactions as well as examine the rotation and evolution of the 120 degree phase. The goal of this work is to gain a general understanding of the magnetic fingerprint for these configurations for experimental methods and identification. |
Friday, March 19, 2021 11:42AM - 11:54AM Live |
Y39.00002: Fracton behavior in frustrated kagome spin models Johannes Reuther, Max Hering, Han Yan Fractons are topological quasiparticles characterized by a limited mobility. While there exists a variety of models displaying this behavior, typical fracton systems require rather complicated many-particle interactions. Here, we discuss fracton behavior in simple classical spin models on the kagome lattice with frustrated two-body interactions only. The spin degrees of freedom may either be defined as three-state Potts, XY, or Heisenberg spins. The observed isolated fractons as well as bound fracton pairs in the three-state Potts model, however, behave considerably different compared to conventional type-I and type-II fracton models. An interpretation in terms of type-I fracton behavior and the formulation of an effective symmetric tensor gauge theory is still possible when defining the system as a 2D cut of a 3D cubic lattice model. Our classical Monte-Carlo simulations indicate a crossover into a glassy phase at low temperatures. Considering XY spins, the system may host fractional vortex excitations whose real-space locations are closely correlated with those of fractons. Finally, in the case of Heisenberg spins, the energy barriers of fractons vanish such that they are no longer stable. |
Friday, March 19, 2021 11:54AM - 12:06PM Live |
Y39.00003: Thermal and dynamical properties of the S=1/2 bilayer breathing-kagome Heisenberg magnet - application to Ca10Cr7O28 - Tokuro Shimokawa, Rico Pohle, Han Yan, Nicholas Shannon Recent experimental studies suggested that Ca10Cr7O28 [1] is a promising candidate for a quantum spin liquid (QSL) ground state. Several theoretical studies applied to the proposed Hamiltonian and captured many features of experiments; however, they involved some level of approximation and left open the role of quantum effects at finite temperature. |
Friday, March 19, 2021 12:06PM - 12:18PM Live |
Y39.00004: Role of chemical pressure on the electronic and magnetic properties of the spin-1/2 kagome mineral averievite Dibyendu Dey, Antia Botana The electronic and magnetic properties of the S=1/2 kagome mineral averievite Cu5V2O10(CsCl) and its phosphate analog Cu5P2O10(CsCl) have been investigated using density functional theory calculations. The crystal structure of these compounds contains Cu2+ kagome layers sandwiched between Cu2+-V5+/Cu2+-P5+ honeycomb layers with the Cu atoms of neighboring kagome and honeycomb planes forming pyrochlore slabs. The induced chemical pressure effect upon substitution of V by P causes significant changes in the electronic and magnetic properties. Our calculations show that the in-plane antiferromagnetic (AFM) nearest-neighbor coupling in the kagome layers remains similar in both V- and P-based materials. In contrast, the inter-plane AFM coupling between kagome and honeycomb layers becomes five times larger in P-variant, increasing the degree of magnetic frustration in the constituting pyrochlore slabs. By substituting honeycomb Cu2+ with Zn2+, the kagome S=1/2 planes can be isolated and become the only magnetically active ones, making Zn-substituted averievite a promising candidate for quantum spin liquid behavior. |
Friday, March 19, 2021 12:18PM - 12:30PM Live |
Y39.00005: Resonant inelastic x-ray scattering study of vector chiral ordered kagome antiferromagnet Trinanjan Datta, Zijian Xiong, Dao-Xin Yao We study the resonant inelastic x-ray scattering (RIXS) features of vector chiral ordered kagome antiferromagnets. Utilizing a group theoretical formalism that respects lattice site symmetry, we calculated the L -edge magnon contribution for the vesignieite compound BaCu3V2O8(OH)2. We show that polarization dependence of the L -edge RIXS spectrum can be used to track magnon branches. We predict a non-zero L -edge signal in the non-cross π-π polarization channel. At the K -edge, we derived the two-site effective RIXS and Raman scattering operator for two-magnon excitation in vesignieite using the Shastry-Shraiman formalism. Our derivation considers spin-orbit coupling effects in virtual hopping processes. We find vector chiral correlation (four-spin) contribution that is proportional to the RIXS spectrum. Our scattering operator formalism can be applied to a host of non-collinear non-coplanar magnetic materials at both the L and K -edge. We demonstrate that vector chiral correlations can be accessed by RIXS experiments. |
Friday, March 19, 2021 12:30PM - 12:42PM Live |
Y39.00006: Topological Quantum Many-Body Scars in Quantum Dimer Models on the Kagome Lattice Julia Wildeboer, Alexander Seidel, Srivatsa N S, Anne E. B. Nielsen, Onur Erten We present a general strategy to turn classes of frustration free lattice models into similar classes containing quantum many-body scars within the bulk of their spectrum while preserving much or all of the original symmetry. Focusing on a class of quantum dimer models, we choose a representative model living on the kagome lattice and discuss numerous results of the embedded scar state(s) and its parent Hamiltonian including entanglement properties and thermalization utilizing an exact diagonalization study of lattices of up to 60 sites. |
Friday, March 19, 2021 12:42PM - 12:54PM Live |
Y39.00007: Spin-dynamics of the Lieb lattice with variable exchange parameters Jose H Pagan, Avadh Saxena, Jason Haraldsen In this talk, we discuss the effects of variable exchange interactions on the spin dynamics of the Lieb lattice. Using a Holstein-Primakoff expansion of the Heisenberg Hamiltonian, we determine the magnetic phase diagram for various magnetic configurations as well as the spin-wave dynamics with multiple nearest-neighbor and next-nearest-neighbor interactions. We also discuss the evolution of a Lieb lattice transforming into a Kagome lattice and how the accompanying respective magnetic configurations change during this process, and whether they remain stable. |
Friday, March 19, 2021 12:54PM - 1:06PM Not Participating |
Y39.00008: Characterizing the Spin-½ Heisenberg model on the triangular lattice through the Dynamical Spin Structure Factor Ta Tang, Brian John Moritz, Thomas Devereaux The ground state phase of the spin-1/2 Heisenberg model on the triangular lattice with nearest-neighbor exchange J1 can be frustrated by the next nearest neighbor coupling J2. While both small and large values of J2/J1 lead to magnetically ordered phases, a spin liquid phase with short correlation length can be established at intermediate values. However, the nature of this spin liquid phase remains under debate, with finite size DMRG calculations suggesting a gapped Z2 spin liquid phase, but also showing possible gapless spinon excitations. Here, we use exact diagonalization on a series of finite-size clusters to analyze the character of the ground state and lowest-lying the excited states of the model for various values of J2. We further characterize the evolution of the model as a function of J2 by analyzing the dynamical spin structure factor S(q,w) to provide key information on changes of the underlying magnetic structure. |
Friday, March 19, 2021 1:06PM - 1:18PM Live |
Y39.00009: Magnetization plateaux in the anisotropic triangular quantum antiferromagnet Cs2CoBr4 Kirill Povarov, Leonardo Facheris, Stefan Velja, Dominic Blosser, Zewu Yan, Severian Gvasaliya, Andrey Zheludev We report the highly unusual magnetic phase diagram of a novel frustrated antiferromagnet Cs2CoBr4. Strong planar single ion anisotropies are competing in the neighboring cobalt S=3/2 chains that are, in turn, coupled in geometrically frustrated zig-zag fashion. The resulting effective Hamiltonan is pseudospin-1/2 and features both "triangular" geometric frustration and bond-dependent anisotropies in the spirit of Kitaev model. By means of calorimetric studies we find an intricate and highly anisotropic phase diagram below 1 K. In the particular high-symmetry direction we find up to five magnetic phases before the pseudospins-1/2 become nearly polarized at 6 T. Further ultralow-T investigation with the Faraday balance magnetometer demonstrates that two of these five phases are plateaux, with M=0 and M≈1/3 in terms of the pseudospin magnetization. We discuss how this behavior stems from the proposed Hamiltonian and argue that Cs2CoBr4 represents a novel type of frustration for a 3d transition metal ion-based magnet. |
Friday, March 19, 2021 1:18PM - 1:30PM Live |
Y39.00010: Measurement of a 1/2 magnetization plateau in a triangular antiferromagnet Shannon Haley, Sophie Weber, Taylor Cookmeyer, Daniel E Parker, Eran Maniv, Nikola Maksimovic, Caolan John, Spencer Doyle, Ariel Maniv, Sanath Ramakrishna, Arneil P Reyes, John Singleton, Joel Ellis Moore, Jeffrey Neaton, James Analytis Frustrated magnetic systems lend themselves to a wealth of nontrivial behaviors. Among these are plateaus in magnetization with the application of an external field, which can result from quantum fluctuations or a strong magnetocrystalline anisotropy. The existence of these plateaus at specific fractions of the saturated magnetization has been observed in a handful of systems with distinct physics. This talk will discuss our discovery of a ½ magnetization plateau in a frustrated antiferromagnet on a triangular lattice using fields up to 60T, as well as our minimal model, informed by ab initio calculations, that predicts this behavior. |
Friday, March 19, 2021 1:30PM - 1:42PM Live |
Y39.00011: Lattice dynamics in the Kagome metal Sc3Mn3Al7Si5 Xiyang Li, Dalmau Reig-i-Plessis, Pengfei Liu, Shan Wu, Alannah Hallas, Matthew Brandon Stone, Collin Leslie Broholm, Meigan Aronson The Mn atoms in the hexagonal metal Sc3Mn3Al7Si5 are arranged on a Kagome lattice. We have studied the phonon density of states (DOS) in Sc3Mn3Al7Si5 using both inelastic neutron scattering (INS) measurements and ab initio calculations. The simulation of the single phonon DOS agrees well with the results of INS measurement, matching both the peak positions and their intensities. This consistency between experimental and theoretical results suggests that phonon anharmonicity is not significant in this material, and further evidence comes from a very small multiphonon contribution to the measured DOS, and the absence of softening or broadening of the phonon DOS with increasing temperature. The partial phonon DOS calculation shows that the phonon DOS arises mainly from the Sc atoms, while that of the Mn atoms makes only a small contribution. The lattice component of the specific heat is estimated from the INS measured phonon DOS, finding that it accounts for ~82% of the measured specific heat at 200 K. After the lattice component of the specific heat, the lattice dilational specific heat, and the electronic specific heat are subtracted, a magnetic contribution to the specific heat is inferred. |
Friday, March 19, 2021 1:42PM - 1:54PM Live |
Y39.00012: Unconventional phase transitions in the classical J1-J2 XY antiferromagnet on the kagome lattice Fumiya Kakizawa, Takahiro Misawa, Hiroshi Shinaoka Frustrated XY antiferromagnets have been investigated extensively in the past decades due to exotic phenomena arising from geometrical frustration. The classical nearest-neighbor XY antiferromagnet on the kagome lattice is a typical 2D frustrated magnet with macroscopic ground-state degeneracy. The macroscopic degeneracy can be lifted by small perturbations, such as thermal fluctuations. This gives rise to various exotic phenomena, including emergent fractional vortex pairs. A fundamental but unresolved issue is how next-nearest-neighbor interaction affects the competition of degenerated states at finite temperature. In this talk, we investigate the finite-temperature phase diagram of classical J1-J2 XY antiferromagnets on the kagome lattice through extensive Monte Carlo simulations. We show that a weak antiferromagnetic J2 induces an unconventional first-order transition at low temperatures. Furthermore, in the vicinity of the first-order transition, we find two competing quasi-long-range orders with different wavevectors. We will discuss the relation between the phase competition and the unconventional first-order transition. |
Friday, March 19, 2021 1:54PM - 2:06PM Live |
Y39.00013: STM study of electron-phonon many-body interplay in a frustrated paramagnet Yuxiao Jiang, Jiaxin Yin, Nana Shumiya, Sougata Mardanya, Songtian Zhang, Zahid Hasan, Hechang Lei We use state-of-the-art scanning tunneling microscopy/spectroscopy to discover unusual electronic coupling to flat-band phonons in a layered kagome paramagnet, CoSn. We image the kagome structure with unprecedented atomic resolution and observe the striking bosonic mode interacting with dispersive kagome electrons near the Fermi surface. At this mode energy, the fermionic quasi-particle dispersion exhibits a pronounced renormalization, signaling a giant coupling to bosons. Through the self-energy analysis, first-principles calculation, and a lattice vibration model, we present evidence that this mode arises from the geometrically frustrated phonon flat-band, which is the lattice bosonic analog of the kagome electron flat-band. Our findings provide the first example of kagome bosonic mode (flat-band phonon) in electronic excitations and its strong interaction with fermionic degrees of freedom in kagome-net materials. |
Friday, March 19, 2021 2:06PM - 2:18PM Live |
Y39.00014: Stuffed honeycomb lattice in magnetic field Jyotisman Sahoo, Rebecca Flint We explore the effect of magnetic field on the stuffed honeycomb lattice, a honeycomb lattice with a superimposed triangular lattice formed by sites at the center of each hexagon that interpolates between the honeycomb lattice and its dual. One potential candidate hosting this lattice is the compound GdInO3 with large S = 7/2 Gd moments. Its phase diagram in a magnetic field is particularly interesting, as in addition to the expected 1/3 magnetization plateau, there is a mysterious magnetization jump at 2/3rds of the saturation magnetization value. In the current work, we analyze the phase diagram of the Heisenberg model with Dzyaloshinskii-Moriya (DM) interactions on the stuffed honeycomb lattice in a magnetic field. We estimate that the relative magnitudes of the DM and Heisenberg interactions are similar to 3d transition metals. Interestingly, we find that the competition between DM interactions and quantum fluctuations can give rise to additional first order phase transitions that might explain the 2/3 magnetization jump. |
Friday, March 19, 2021 2:18PM - 2:30PM Live |
Y39.00015: Spin excitations in single crystal barlowite Cu4(OD)6FBr—a kagome quantum antiferromagnet Wei He, Rebecca Smaha, Jiajia Wen, Mingde Jiang, Yiming Qiu, Young Sang Lee Barlowite is the parent compound of a new kagome quantum spin liquid candidate Zn-barlowite. We synthesized a new variant of barlowite with a higher symmetry crystal structure at low temperatures. This new high-symmetry barlowite undergoes two consecutive magnetic transitions below ~10 K. Our previous elastic neutron scattering revealed that in the ground state the spins order in a pinwheel q=0 structure, while between the two magnetic transition temperatures the kagome spins likely form a novel valence bond crystal (VBC). In this talk, I will present our recent inelastic neutron scattering data taken on coaligned crystals. The data collected in both the spin ordered and the VBC states exhibit distinct features that cannot be explained by trivial spin waves. Our study provides crucial information regarding the exotic spin excitations in barlowite. |
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