The ordered low-dimensional frustrated magnets challenge the nonlinear spin-wave theories - PowerPoint Presentation

The ordered low-dimensional frustrated magnets challenge the nonlinear spin-wave theories
The ordered low-dimensional frustrated magnets challenge the nonlinear spin-wave theories

The ordered low-dimensional frustrated magnets challenge the nonlinear spin-wave theories - Description


The research conducted at ORNLs Spallation Neutron Source and High Flux Isotope Reactor was sponsored by the Scientific User Facilities Division Office of Basic Energy Sciences US Department of ID: 646157 Download Presentation

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energy neutron spin magnon neutron energy magnon spin theoretical decay observed triangular framework lattice ordered broadening reveal hamiltonian exchange

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The ordered low-dimensional frustrated magnets challenge the nonlinear spin-wave theories

The research conducted at ORNL's Spallation Neutron Source and High Flux Isotope Reactor was sponsored by the Scientific User Facilities Division, Office of Basic Energy Sciences, US Department of Energy. Experiments were performed at the ORNL High Flux Isotope Reactor’s HB1A, HB1, HB3A, and CG4C, and Spallation Neutron Source’s CNCS instruments.

a-b The inelastic neutron scattering measurements and nonlinear spin-wave simulation of the spectra of Ba3CoSb2O9 as a function of the momentum and energy transfer at T = 1.5K. c The constant-q scans near M1 point showing the broadened magnon line-widths and their decay. In addition, the two-magnon continuum was observed. d Constant-energy cut at 1.3 meV, showing the triangular lattice shape associated with the zone boundary excitation.

J. Ma, Y. Kamiya, Tao Hong, H. B. Cao, G. Ehlers, W. Tian, C. D. Batista, Z. L. Dun, H. D. Zhou, and M. Matsuda, Static and Dynamical Properties of the Spin-1/2 Equilateral Triangular-Lattice Antiferromagnet Ba3CoSb2O9. Physical Review Letters (in press).

(d)

(c)

(b)

Scientific Achievement

R

esults on an ordered low dimensional frustrated magnet suggest a new theoretical framework is needed for adequate description.

Significance and Impact

The

S=1/2

triangular-lattice Heisenberg

antiferromagnet

,

Ba

3

CoSb

2

O

9

, is a typical system to study the combination of the frustration, quantum fluctuations

and low dimensionality

.

In this context, the authors confirm the

120°order in

the ab-plane at zero-field and determine the exchange constants of the quasi-2D XXZ Hamiltonian. More importantly, they

reveal

that the

semiclassical

treatment is inadequate to explain the observed

magnon

decay and the associated line broadening, thereby pointing to a need for developing an alternative theoretical framework

.

Research Details

The magnetic structure was confirmed by neutron diffraction.

The exchange and anisotropy parameters were determined by inelastic neutron scattering with a

quasi-2D spin Hamiltonian

.

The observed magnon decay and the broadening dispersions reveal that a new theoretical framework is needed

.

Shom More....