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Title: In-Gap Spin Excitations and Finite Triplet Lifetimes in the Dilute Singlet Ground State System SrCu{sub 2-x}Mg{sub x}(BO{sub 3}){sub 2}

Abstract

High resolution neutron scattering measurements on a single crystal of SrCu{sub 2-x}Mg{sub x}(BO{sub 3}){sub 2} with x{approx}0.05 reveal the presence of new spin excitations within the gap of this quasi-two-dimensional, singlet ground state system. The application of a magnetic field induces Zeeman-split states associated with S=1/2 unpaired spins which are antiferromagnetically correlated with the bulk singlet. Substantial broadening of both the one- and two-triplet excitations in the doped single crystal is observed, as compared with pure SrCu{sub 2}(BO{sub 3}){sub 2}. Theoretical calculations using a variational algorithm and a single quenched magnetic vacancy on an infinite lattice are shown to qualitatively account for these effects.

Authors:
; ;  [1];  [2];  [1];  [3]; ;  [4];  [2];  [5]
  1. Department of Physics and Astronomy, McMaster University, Hamilton, Ontario L8S 4M1 (Canada)
  2. J. Stefan Institute, SI-1000 Ljubljana (Slovenia)
  3. (Canada)
  4. Rutherford Appleton Laboratory, ISIS Pulsed Neutron Facility, Chilton, Didcot, Oxon OX110QX (United Kingdom)
  5. (Slovenia)
Publication Date:
OSTI Identifier:
20861488
Resource Type:
Journal Article
Resource Relation:
Journal Name: Physical Review Letters; Journal Volume: 97; Journal Issue: 24; Other Information: DOI: 10.1103/PhysRevLett.97.247206; (c) 2006 The American Physical Society; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
36 MATERIALS SCIENCE; ALGORITHMS; BORATES; COPPER COMPOUNDS; DOPED MATERIALS; EXCITATION; GROUND STATES; LIFETIME; MAGNESIUM COMPOUNDS; MAGNETIC FIELDS; MONOCRYSTALS; NEUTRON DIFFRACTION; SPIN; STRONTIUM COMPOUNDS; TRIPLETS; TWO-DIMENSIONAL CALCULATIONS; VACANCIES; VARIATIONAL METHODS; ZEEMAN EFFECT

Citation Formats

Haravifard, S., Dunsiger, S. R., Dabkowska, H. A., El Shawish, S., Gaulin, B. D., Canadian Institute for Advanced Research, 180 Dundas Street W, Toronto, Ontario M5G 1Z8, Telling, M. T. F., Perring, T. G., Bonca, J., and Faculty of Mathematics and Physics, University of Ljubljana, SI-1000 Ljubljana. In-Gap Spin Excitations and Finite Triplet Lifetimes in the Dilute Singlet Ground State System SrCu{sub 2-x}Mg{sub x}(BO{sub 3}){sub 2}. United States: N. p., 2006. Web. doi:10.1103/PHYSREVLETT.97.247206.
Haravifard, S., Dunsiger, S. R., Dabkowska, H. A., El Shawish, S., Gaulin, B. D., Canadian Institute for Advanced Research, 180 Dundas Street W, Toronto, Ontario M5G 1Z8, Telling, M. T. F., Perring, T. G., Bonca, J., & Faculty of Mathematics and Physics, University of Ljubljana, SI-1000 Ljubljana. In-Gap Spin Excitations and Finite Triplet Lifetimes in the Dilute Singlet Ground State System SrCu{sub 2-x}Mg{sub x}(BO{sub 3}){sub 2}. United States. doi:10.1103/PHYSREVLETT.97.247206.
Haravifard, S., Dunsiger, S. R., Dabkowska, H. A., El Shawish, S., Gaulin, B. D., Canadian Institute for Advanced Research, 180 Dundas Street W, Toronto, Ontario M5G 1Z8, Telling, M. T. F., Perring, T. G., Bonca, J., and Faculty of Mathematics and Physics, University of Ljubljana, SI-1000 Ljubljana. Fri . "In-Gap Spin Excitations and Finite Triplet Lifetimes in the Dilute Singlet Ground State System SrCu{sub 2-x}Mg{sub x}(BO{sub 3}){sub 2}". United States. doi:10.1103/PHYSREVLETT.97.247206.
@article{osti_20861488,
title = {In-Gap Spin Excitations and Finite Triplet Lifetimes in the Dilute Singlet Ground State System SrCu{sub 2-x}Mg{sub x}(BO{sub 3}){sub 2}},
author = {Haravifard, S. and Dunsiger, S. R. and Dabkowska, H. A. and El Shawish, S. and Gaulin, B. D. and Canadian Institute for Advanced Research, 180 Dundas Street W, Toronto, Ontario M5G 1Z8 and Telling, M. T. F. and Perring, T. G. and Bonca, J. and Faculty of Mathematics and Physics, University of Ljubljana, SI-1000 Ljubljana},
abstractNote = {High resolution neutron scattering measurements on a single crystal of SrCu{sub 2-x}Mg{sub x}(BO{sub 3}){sub 2} with x{approx}0.05 reveal the presence of new spin excitations within the gap of this quasi-two-dimensional, singlet ground state system. The application of a magnetic field induces Zeeman-split states associated with S=1/2 unpaired spins which are antiferromagnetically correlated with the bulk singlet. Substantial broadening of both the one- and two-triplet excitations in the doped single crystal is observed, as compared with pure SrCu{sub 2}(BO{sub 3}){sub 2}. Theoretical calculations using a variational algorithm and a single quenched magnetic vacancy on an infinite lattice are shown to qualitatively account for these effects.},
doi = {10.1103/PHYSREVLETT.97.247206},
journal = {Physical Review Letters},
number = 24,
volume = 97,
place = {United States},
year = {Fri Dec 15 00:00:00 EST 2006},
month = {Fri Dec 15 00:00:00 EST 2006}
}
  • Magnetic susceptibility, Cu NQR, and high-filed magnetization have been measured in polycrystalline SrCu{sub 2}( BO{sub 3}){sub 2} having a two-dimensional (2D) orthogonal network of Cu dimers. This cuprate provides a new class of 2D spin-gap system ({Delta}=30 K ) in which the ground state can be solved {open_quotes}exactly.{close_quotes} Furthermore, in the magnetization, two plateaus corresponding to (1)/(4) and (1)/(8) of the full Cu moment were first observed for 2D quantum spin systems. {copyright} {ital 1999} {ital The American Physical Society}
  • We report the first crystallographic study within the low-temperature (<40 K) spin-gap region of the two-dimensional frustrated antiferromagnet SrCu{sub 2}(BO{sub 3}){sub 2}. The crystal system does not deviate from the tetragonal I-42m space group symmetry. However, our high-resolution neutron powder diffraction measurements uncover subtle structural modifications below 34 K, concomitant to the formation of the dimer singlet ground state. Intimate spin-lattice coupling leads to negative thermal expansion of the tetragonal structure, which reflects into particular local lattice adjustments. The extracted structural parameters suggest the reduction of the buckling found in the copper-borate planes and the strengthening of the leading, in-planemore » intra-dimer superexchange interaction. The observed contraction along the c-axis, associated with the inter-dimer exchange in adjacent layers, indicates the involvement of weaker three-dimensional interactions in the magnetic properties. The rules posed by the crystal symmetry do not preclude Dzyaloshinsky-Moriya interactions, which therefore remain as an important source of spin anisotropy necessary to rationalise the ground state behaviour. - Abstract: We report the first crystallographic study within the low-temperature spin-gap region of the two-dimensional frustrated antiferromagnet SrCu{sub 2}(BO{sub 3}){sub 2}. Subtle spin-lattice coupling was unveiled in the low-temperature region. Display Omitted« less
  • Measurements of the thermal conductivity as a function of temperature and magnetic field in the 2D dimer spin system SrCu{sub 2}( BO{sub 3}){sub 2} are presented. In zero magnetic field the thermal conductivity along and perpendicular to the magnetic planes shows a pronounced double-peak structure as a function of temperature. The low-temperature maximum is drastically suppressed with increasing magnetic field. Our quantitative analysis reveals that the heat current is due to phonons and that the double-peak structure arises from pronounced resonant scattering of phonons by magnetic excitations.
  • An exact mapping between quantum spins and boson gases provides fresh approaches to the creation of quantum condensates and crystals. Here we report on magnetization measurements on the dimerized quantum magnet SrCu 2(BO 3) 2 at cryogenic temperatures and through a quantum-phase transition that demonstrate the emergence of fractionally filled bosonic crystals in mesoscopic patterns, specified by a sequence of magnetization plateaus. We apply tens of Teslas of magnetic field to tune the density of bosons and gigapascals of hydrostatic pressure to regulate the underlying interactions. Simulations help parse the balance between energy and geometry in the emergent spin superlattices.more » In conclusion, the magnetic crystallites are the end result of a progression from a direct product of singlet states in each short dimer at zero field to preferred filling fractions of spin-triplet bosons in each dimer at large magnetic field, enriching the known possibilities for collective states in both quantum spin and atomic systems.« less
  • An exact mapping between quantum spins and boson gases provides fresh approaches to the creation of quantum condensates and crystals. Our magnetization measurements on the dimerised quantum magnet SrCu 2(BO 3) 2 at cryogenic temperatures and through a quantum phase transition demonstrate the emergence of fractionally-filled bosonic crystals in mesoscopic patterns, specified by a sequence of magnetization plateaus. We apply tens of Teslas of magnetic field to tune the density of bosons and GigaPascals of hydrostatic pressure to regulate the underlying interactions. Simulations help parse the balance between energy and geometry in the emergent spin superlattices. The magnetic crystallites aremore » the end result of a progression from a direct product of singlet states in each short dimer at zero field to preferred filling fractions of spin triplet bosons in each dimer at large magnetic field, enriching the known possibilities for collective states in both quantum spin and atomic systems.« less