Bulletin of the American Physical Society
APS March Meeting 2017
Volume 62, Number 4
Monday–Friday, March 13–17, 2017; New Orleans, Louisiana
Session P48: Frustrated Magnetism: Quantum Spin IceFocus

Hide Abstracts 
Sponsoring Units: GMAG DMP Chair: Shigeki Onoda, RIKEN Room: 395 
Wednesday, March 15, 2017 2:30PM  3:06PM 
P48.00001: Phase diagram and spin dynamics of the frustrated pyrochlore magnet Yb$_2$Ti$_2$O$_7$ in applied field Invited Speaker: Radu Coldea The frustrated pyrochlore magnet Yb$_2$Ti$_2$O$_7$ has been proposed as a candidate "quantum spin ice" material. Here we report singlecrystal inelastic neutron scattering measurements of the spin dynamics and complementary specific heat data to map the phase diagram in magnetic fields applied along a cubic [001] direction, not explored experimentally in detail before. At the highest magnetic fields probed (9 T) we observe in addition to dominant onemagnon excitations also a broad scattering continuum at higher energies, attributed to twomagnon excitations, not detected in previous neutron scattering studies. We characterize how the spectrum evolves upon lowering field and observe how highenergy magnons decay when they overlap with the highenergy continuum and the lowenergy magnons have their dispersion bandwidth suppressed and in zero field disappear altogether over a wide range of the Brillouin zone where the inelastic signal is dominated by a scattering continuum extended over a broad energy range. Through fits of the dispersion relations at high fields we propose a reevaluation of the spin Hamiltonian to consistently explain all existing spin dynamics data for different field directions and propose a phenomenological model of the evolution of the spin dynamics in applied field [1]. We acknowledge support from EPSRC (UK). [1] J. D. Thompson, P. McClarty, D. Prabhakaran, I. Cabrera, T. Guidi and R. Coldea, in preparation. [Preview Abstract] 
Wednesday, March 15, 2017 3:06PM  3:18PM 
P48.00002: Quantum spin ice under a [111] magnetic field: from pyrochlore to kagom\'{e} Troels Bojesen, Shigeki Onoda We present the global phase diagram of a minimal XXZ quantum spin ice model on the pyrochlore lattice under a $[111]$ magnetic field, obtained by unbiased quantum MonteCarlo simulations. In zero field and for moderate quantum fluctuations, the model crosses over from classical pyrochlore spin ice to a U(1) quantum spin liquid upon cooling. Increasing the field takes the system into the kagom\'e spin ice region with a $1/3$ magnetization plateau, where the fluctuations are mainly restricted to the kagom\'e layers perpendicular to the field direction. Then, shortrange longitudinal spin correlations of a $\sqrt{3}\times\sqrt{3}$ pattern gradually appears, as they evolve into a longrange order at the ground state in the decoupled pure kagom\'e limit. A further increase in the magnetic field below the saturation field induces a finitetemperature phase transition to a 3D longrange ordered phase of the transverse spin components perpendicular to the local $\langle111\rangle$ axes. This transition either belongs to the 3D XY universality class or is weakly firstorder. The possible relevance to magnetic rareearth pyrochlore oxides is discussed. [Preview Abstract] 
Wednesday, March 15, 2017 3:18PM  3:30PM 
P48.00003: Low temperature specific heat characterization of the geometrically frustrated magnetic compound Yb$_{2}$Ti$_{2}$O$_{7}$ David Pomaranski, Hanna Dabkowska, Casey Marjerrison, Kate Ross, Bruce Gaulin, Jan Kycia Yb$_{2}$Ti$_{2}$O$_{7}$ is a geometrically frustrated magnet that has been recently proposed as a quantum spin liquid (QSL) candidate. This would have an emergent U(1) gauge structure, supporting emergent quasiparticles and a continuum of gapless spin excitations, which would give rise to a cubic power law dependence of specific heat down to zero temperature.[L. Savary and L. Balents, Phys. Rev. B \textbf{87}, 205130 (2013)] Low temperature specific heat measurements have identified the presence of a sharp transition at 0.26 K.[K. A. Ross et al., Phys. Rev. B \textbf{84}, 174442 (2011)] We will present results quantifying the specific heat of a polycrystalline Yb$_{2}$Ti$_{2}$O$_{7}$ sample below the observed transition. [Preview Abstract] 
Wednesday, March 15, 2017 3:30PM  3:42PM 
P48.00004: Semiclassical Approach to Quantum Spin Ice Claudio Castelnovo, Benoit Dou\c{c}ot, Michal P. Kwasigroch We propose a semiclassical description of the lowenergy properties of quantum spin ice in the strong Ising limit. Within the framework of a semiclassical, perturbative Villain expansion, that can be truncated at arbitrary order, we give an analytic and quantitative treatment of the deconfining phase. We find that photonphoton interactions significantly renormalise the speed of light and split the two transverse photon polarisations at intermediate wavevectors. We calculate the photon velocity and the ground state energy to first and second order in perturbation theory, respectively. Both are in good agreement with recent numerical simulations. We further compute the classical energy of the vison excitation. [Preview Abstract] 
Wednesday, March 15, 2017 3:42PM  4:18PM 
P48.00005: Low energy electrodynamics of the quantum spin ice of Yb$_2$Ti$_2$O$_7$ Invited Speaker: N. Peter Armitage In condensed matter systems, the formation of long range order (LRO) with broken symmetry is often accompanied by new types of excitations. However, in many magnetic pyrochlore oxides, geometrical frustration suppresses conventional LRO while at the same time nontrivial spin correlations are observed. For such materials, a natural question to ask then is what is the nature of the excitations in this highly correlated state without broken symmetry? Frequently the application of a symmetry breaking field can stabilize excitations whose properties still reflect certain aspects of the anomalous state without longrange order. Here we report evidence of novel magnetic excitations in the quantum spin ice material Yb$_2$Ti$_2$O$_7$, obtained from timedomain terahertz spectroscopy (TDTS) in both zero and finite applied field. In large applied fields, both magnon and twomagnonlike excitations are observed in a <001> directed magnetic field illustrating the stabilization of a field induced LRO state. The gfactors of these excitations are dramatically enhanced in the lowfield limit, showing a crossover of these one and twomagnon states into features consistent with quantum stringlike excitations proposed to exist in quantum spin ice in a small <001> applied field. In zero magnetic field, we report a combined time domain terahertz spectroscopy (TDTS) and microwave cavity study of Yb$_2$Ti$_2$O$_7$ to probe its complex dynamic magnetic susceptibility. We find that the form of the susceptibility is consistent with monopole motion and a magnetic monopole conductivity can be defined and measured. Using the unique phase sensitive capabilities of these optical techniques, we observe a sign change in the reactive part of the magnetic response. In generic models of monopole motion this is only possible through introducing inertial effects, e.g. a mass dependent term, to the equations of motion. [Preview Abstract] 
Wednesday, March 15, 2017 4:18PM  4:30PM 
P48.00006: Quadrupolar Order in Quantum Spin Ice Nic Shannon, Mathieu Taillefumier, Owen Benton, Ludovic Jaubert Quantum effects in spin ice can modelled using an XXZ model on the pyrochlore lattice. For unfrustrated interactions, $J_\pm > 0$, this model is accessible to quantum Monte Carlo simulations, and supports a quantum spin liquid ground state for $0 < J_\pm \sim < 0.05 J_{zz}$. Here we present a study of this model for frustrated interactions, $J_\pm < 0$, using a combination of classical Monte Carlo and semiclassical moleculardynamics simulations. We find that, for $J_\pm < 0.5 J_{zz}$, the spin liquid gives way with a phase with hidden quadrupolar order. [Preview Abstract] 
(Author Not Attending)

P48.00007: Mesonic states in quantum spin ice Olga Petrova, Roderich Moessner, Shivaji Sondhi We study magnetic monopoles in quantum spin ice, whose dynamics is induced by a transverse field term. We find that the bipartiteness of the state graph of the model and the local spin ice rule constraints result in the presence of an approximately flat band at the classical energy of the nearest neighbor monopole pair. The degeneracy of the socalled mesonic states making up the flat band splits at the same order as the spin ice ground state manifold. We show that the mesonic states result in a crisp neutron scattering signature of magnetic monopoles in the system, and that the momentum dependence of the structure factor may allow for the detection of quantum fluctuations in a spin ice system near the classical limit. [Preview Abstract] 
Wednesday, March 15, 2017 4:42PM  4:54PM 
P48.00008: Quantum Confinement of Monopole Quasiparticles in a Quantum Spin Ice Chris Wiebe, Paul Sarte, Georg Ehlers, Bruce Gaulin, Cole Mauws, Matt Stone, Stuart Calder, Joshua Hollett, Jason Gardner, John Paul Attfield, Chris Stock, Adam Aczel, Stephen Nagler We report direct spectroscopic evidence of correlations between monopoles in a quantum spin ice. A hierarchy of unequally spaced magnetic excitations has been observed via inelastic neutron spectroscopy in Pr$_{2}$Sn$_{2}$O$_{7}$, resembling the confinement of spin defects in lowdimensional quantum magnets. \footnote{J.~B.~Torrance and M.~Tinkham, Phys. Rev.,\textbf{187}, 2, 587 (1969)} Using a simple linear potential model to fit the excitations,\footnote{R. Coldea \textit{et al.}, Science, \textbf{327}, 177 (2010)} we have estimated the monopole pair creation energy, and calculated a lower bound for the tension between monopolelike quasiparticles. The linear potential model provides a natural explanation as to why detection of these correlations have been so elusive in the canonical dipolar spin ices. This is the first spectroscopic measurement of an effective ``Dirac string'' between magnetic monopoles. [Preview Abstract] 
Wednesday, March 15, 2017 4:54PM  5:06PM 
P48.00009: Octupolar quantum spin ice: controlling spinons in a U(1) quantum spin liquid Yaodong Li, Gang Chen We study the symmetry enriched U(1) quantum spin liquids (QSLs) on the pyrochlore lattice. We point out that the Ce local moment of the newly discovered pyrochlore QSL candidate Ce2Sn2O7, is a dipoleoctupole doublet. The generic model for these unusual doublets supports two distinct symmetry enriched U(1) QSL ground states in the corresponding quantum spin ice regimes. These two U(1) QSLs are dubbed dipolar U(1) QSL and octupolar U(1) QSL. While the dipolar U(1) QSL has been discussed in many contexts, the octupolar U(1) QSL is rather unique. Based on the symmetry properties of the dipoleoctupole doublets, we predict the peculiar physical properties of the octupolar U(1) QSL, elucidating the unique spectroscopic properties in the external magnetic fields. We further predict the AndersonHiggs transition from the octupolar U(1) QSL driven by the external magnetic fields. We identify the experimental relevance with the candidate material Ce2Sn2O7 and other dipoleoctupole doublet systems. [Preview Abstract] 
Wednesday, March 15, 2017 5:06PM  5:18PM 
P48.00010: Firstprinciples design of the spinel iridate Ir$_2$O$_4$ for high temperature quantum spin ice Shigeki Onoda, Fumiyuki Ishii Insulating magnetic rareearth pyrochlores related to spin ice host emergent bosonic monopolar quasiparticles. These quantum spin ice monopoles obey a magnetic analogue of quantum electrodynamics, opening a route to a magnetic analogue of electronics. However, the energy scales of the interactions among rareearth moments are so low as 1~K that the possible quantum coherence can only be achieved at subKelvins. This too low energy scale hinders advances in fundamental understandings and potential applications. Here, we desgin hightemperature quantum spin ice materials from first principles. It is shown that the $A$site deintercalated spinel iridate Ir$_2$O$_4$, which has been experimentally grown as epitaxial thin films, is a promising candidate for quantum spin ice with a spinicerule interaction of a few tens of meV. Controlling electronic structures of Ir$_2$O$_4$ through substrates, it is possible to tune magnetic interactions so that a magnetic Coulomb liquid persists at high temperatures. [Preview Abstract] 
Follow Us 
Engage
Become an APS Member 
My APS
Renew Membership 
Information for 
About APSThe American Physical Society (APS) is a nonprofit membership organization working to advance the knowledge of physics. 
© 2020 American Physical Society
 All rights reserved  Terms of Use
 Contact Us
Headquarters
1 Physics Ellipse, College Park, MD 207403844
(301) 2093200
Editorial Office
1 Research Road, Ridge, NY 119612701
(631) 5914000
Office of Public Affairs
529 14th St NW, Suite 1050, Washington, D.C. 200452001
(202) 6628700