Evidence of quantum dimer excitations in Sr3Ir2O7

@article{ ISI:000357485100009,
Author = {Sala, M. Moretti and Schnells, V. and Boseggia, S. and Simonelli, L. and
   Al-Zein, A. and Vale, J. G. and Paolasini, L. and Hunter, E. C. and
   Perry, R. S. and Prabhakaran, D. and Boothroyd, A. T. and Krisch, M. and
   Monaco, G. and Ronnow, H. M. and McMorrow, D. F. and Mila, F.},
Title = {{Evidence of quantum dimer excitations in Sr3Ir2O7}},
Journal = {{PHYSICAL REVIEW B}},
Year = {{2015}},
Volume = {{92}},
Number = {{2}},
Month = {{JUL 6}},
Abstract = {{The magnetic excitation spectrum in the bilayer iridate Sr3Ir2O7 has
   been investigated using high-resolution resonant inelastic x-ray
   scattering (RIXS) performed at the iridium L-3 edge and theoretical
   techniques. A study of the systematic dependence of the RIXS spectrum on
   the orientation of the wave-vector transfer Q, with respect to the
   iridium-oxide bilayer, has revealed that the magnon dispersion is
   comprised of two branches well separated in energy and gapped across the
   entire Brillouin zone. Our results contrast with those of an earlier
   study which reported the existence of a single dominant branch. While
   these earlier results were interpreted as two overlapping modes within a
   spin-wave model of weakly coupled iridium-oxide planes, our results are
   more reminiscent of those expected for a system of weakly coupled
   dimers. In this latter approach, the lower-and higher-energy modes find
   a natural explanation as those corresponding to transverse and
   longitudinal fluctuations, respectively. We have therefore developed a
   bond-operator theory which describes the magnetic dispersion in Sr3Ir2O7
   in terms of quantum dimer excitations. In our model, dimerization is
   produced by the leading Heisenberg exchange J(c), which couples iridium
   ions in adjacent planes of the bilayer. The Hamiltonian also includes
   in-plane exchange J, as well as further neighbor couplings and relevant
   anisotropies. The bond-operator theory provides an excellent account of
   the dispersion of both modes, while the measured Q dependence of the
   RIXS intensities is in reasonable qualitative accord with the spin-spin
   correlation function calculated from the theory. We discuss our results
   in the context of the quantum criticality of bilayer dimer systems in
   the presence of anisotropic interactions derived from strong spin-orbit
   coupling.}},
Publisher = {{AMER PHYSICAL SOC}},
Address = {{ONE PHYSICS ELLIPSE, COLLEGE PK, MD 20740-3844 USA}},
Type = {{Article}},
Language = {{English}},
Affiliation = {{Sala, MM (Corresponding Author), European Synchrotron Radiat Facil, BP 220, F-38043 Grenoble, France.
   Sala, M. Moretti; Simonelli, L.; Al-Zein, A.; Paolasini, L.; Krisch, M.; Monaco, G., European Synchrotron Radiat Facil, F-38043 Grenoble, France.
   Schnells, V., Univ Wurzburg, Inst Theoret Phys & Astrophys, D-97074 Wurzburg, Germany.
   Boseggia, S.; Vale, J. G.; Perry, R. S.; McMorrow, D. F., UCL, London Ctr Nanotechnol, London WC1E 6BT, England.
   Boseggia, S.; Vale, J. G.; Perry, R. S.; McMorrow, D. F., UCL, Dept Phys & Astron, London WC1E 6BT, England.
   Boseggia, S., Diamond Light Source Ltd, Didcot OX11 0DE, Oxon, England.
   Simonelli, L., CELLS ALBA Synchrotron Radiat Facil, Barcelona 08290, Spain.
   Hunter, E. C., Ctr Sci Extreme Condit, Edinburgh EH9 3FD, Midlothian, Scotland.
   Prabhakaran, D.; Boothroyd, A. T., Univ Oxford, Dept Phys, Clarendon Lab, Oxford OX1 3PU, England.
   Monaco, G., Univ Trento, Dipartimento Fis, I-38123 Povo, TN, Italy.
   Ronnow, H. M., Ecole Polytech Fed Lausanne, Lab Quantum Magnetism, CH-1015 Lausanne, Switzerland.
   Ronnow, H. M., Univ Tokyo, Inst Solid State Phys, Neutron Sci Lab, Kashiwa, Chiba 2778581, Japan.
   Mila, F., Ecole Polytech Fed Lausanne, Inst Theoret Phys, CH-1015 Lausanne, Switzerland.}},
DOI = {{10.1103/PhysRevB.92.024405}},
Article-Number = {{024405}},
ISSN = {{2469-9950}},
EISSN = {{2469-9969}},
Keywords-Plus = {{SPIN GAPS; FRUSTRATION; STATES}},
Research-Areas = {{Materials Science; Physics}},
Web-of-Science-Categories  = {{Materials Science, Multidisciplinary; Physics, Applied; Physics,
   Condensed Matter}},
ResearcherID-Numbers = {{Zein, Ali Al/F-4393-2019
   Moretti, Marco/AAF-9255-2019
   Krisch, Michael H/U-5662-2018
   Ronnow, Henrik M/A-4953-2009
   McMorrow, Desmond Francis/M-9036-2019
   Simonelli, Laura/I-1963-2015
   Mila, Frederic/R-4871-2019
   McMorrow, Desmond/C-2655-2008
   Vale, James/A-1475-2016
   Monaco, Giulio/AAW-4387-2020
   Sala, Marco Moretti/H-1034-2014
   }},
ORCID-Numbers = {{Moretti, Marco/0000-0002-9744-9976
   Krisch, Michael H/0000-0001-7423-1715
   Ronnow, Henrik M/0000-0002-8832-8865
   McMorrow, Desmond Francis/0000-0002-4947-7788
   Mila, Frederic/0000-0003-4306-7996
   McMorrow, Desmond/0000-0002-4947-7788
   Vale, James/0000-0002-9148-3575
   Monaco, Giulio/0000-0003-2497-6422
   Sala, Marco Moretti/0000-0002-9744-9976
   Giles, Emily/0000-0001-9880-1102}},
Funding-Acknowledgement = {{Swiss National Science FoundationSwiss National Science Foundation
   (SNSF); ERC starters grant TOPOLECTRICS {[}ERC-StG-TOPOLECTRICS-336012];
   Sinergia network Mott Physics Beyond the Heisenberg Model;
   EPSRCEngineering & Physical Sciences Research Council (EPSRC);
   Engineering and Physical Sciences Research CouncilEngineering &
   Physical Sciences Research Council (EPSRC) {[}EP/J017124/1,
   EP/G007357/1, EP/J016713/1, 1268395, 1745233] Funding Source:
   researchfish}},
Funding-Text = {{We gratefully thank C. Henriquet and R. Verbeni for technical assistance
   during the experiments and B. Normand, O. Syljuaasen, and B. Dalla
   Piazza for insightful discussions. The work in Lausanne was supported by
   the Swiss National Science Foundation and its Sinergia network Mott
   Physics Beyond the Heisenberg Model, in London by the EPSRC, and in
   Wurzburg by the ERC starters grant TOPOLECTRICS under
   ERC-StG-TOPOLECTRICS-336012.}},
Number-of-Cited-References = {{40}},
Times-Cited = {{31}},
Usage-Count-Last-180-days = {{0}},
Usage-Count-Since-2013 = {{87}},
Journal-ISO = {{Phys. Rev. B}},
Doc-Delivery-Number = {{CM2BR}},
Unique-ID = {{ISI:000357485100009}},
OA = {{Green Published}},
DA = {{2020-12-22}},
}