ICNS – 2005, Sydney, ICNS – 2005, Sydney, Australia Australia Quasiparticle breakdown in quantum Quasiparticle breakdown in quantum spin liquid spin liquid Collaborators Collaborators • M. B. Stone • D. Reich, T. Hong • C. Broholm Igor Zaliznyak Igor Zaliznyak Neutron Scattering Group, Brookhaven National Laboratory & & OAK RIDGE NATIONAL LABORATORY
O AK R IDGE N ATIONAL L ABORATORY. Quasiparticle breakdown in quantum spin liquid. Igor Zaliznyak Neutron Scattering Group, Brookhaven National Laboratory. Collaborators M. B. Stone D. Reich, T. Hong C. Broholm. &. What is liquid? no shear modulus - PowerPoint PPT Presentation
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ICNS – 2005, Sydney, AustraliaICNS – 2005, Sydney, Australia
Quasiparticle breakdown in quantum spin liquidQuasiparticle breakdown in quantum spin liquid
CollaboratorsCollaborators
• M. B. Stone
• D. Reich, T. Hong
• C. Broholm
Igor ZaliznyakIgor Zaliznyak
Neutron Scattering Group, Brookhaven National Laboratory
&&
OAK RIDGE NATIONAL LABORATORY
ICNS – 2005, Sydney, AustraliaICNS – 2005, Sydney, Australia
What is quantum liquid?What is quantum liquid?• What is liquid?
− no shear modulus− no elastic scattering = no static correlation of density fluctuations
‹ρ(r1,0)ρ (r2,t)› → 0t → ∞
• What is quantum liquid? − all of the above at T → 0 (i.e. at temperatures much lower than inter-particle interactions in the system)
• Elemental quantum liquids:− H, He and their isotopes− made of light atoms strong quantum fluctuations
ICNS – 2005, Sydney, AustraliaICNS – 2005, Sydney, Australia
ε(q)
(Kel
vin)
q (Å-1)
phonon
roton
maxonwhatsgoingon?
Excitations in quantum Bose liquid: superfluid Excitations in quantum Bose liquid: superfluid 44HeHe
Woods & Cowley, Rep. Prog. Phys. 36 (1973)
ICNS – 2005, Sydney, AustraliaICNS – 2005, Sydney, Australia
The “cutoff point” of the quasiparticle spectrum in The “cutoff point” of the quasiparticle spectrum in the quantum Bose-liquidthe quantum Bose-liquid
ICNS – 2005, Sydney, AustraliaICNS – 2005, Sydney, Australia
Spectrum termination in Spectrum termination in 44He: experimentHe: experiment
ICNS – 2005, Sydney, AustraliaICNS – 2005, Sydney, Australia
What is quantum spin liquid?What is quantum spin liquid?
• Quantum liquid state for a system of Heisenberg spins
H = J|| SiSi+||+ JSiSi
• Exchange couplings J||, J through orbital overlaps may be different
− J||/J >> 1 (<<1) parameterize quasi-1D (quasi-2D) case
Coupled chains J||/J>> 1
Coupled planes J||/J<<1• no static spin correlations
‹Siα (0)Sj
β (t)› → 0, i.e. ‹Si
α (0)Sjβ (t)› = 0
• hence, no elastic scattering (e.g. no magnetic Bragg peaks)
t → ∞
ICNS – 2005, Sydney, AustraliaICNS – 2005, Sydney, Australia