Lab Home | Phone | Search
Center for Nonlinear Studies  Center for Nonlinear Studies
 Home 
 People 
 Current 
 Affiliates 
 Visitors 
 Students 
 Research 
 ICAM-LANL 
 Publications 
 Conferences 
 Workshops 
 Sponsorship 
 Talks 
 Colloquia 
 Colloquia Archive 
 Seminars 
 Postdoc Seminars Archive 
 Quantum Lunch 
 Quantum Lunch Archive 
 CMS Colloquia 
 Q-Mat Seminars 
 Q-Mat Seminars Archive 
 P/T Colloquia 
 Archive 
 Kac Lectures 
 Kac Fellows 
 Dist. Quant. Lecture 
 Ulam Scholar 
 Colloquia 
 
 Jobs 
 Postdocs 
 CNLS Fellowship Application 
 Students 
 Student Program 
 Visitors 
 Description 
 Past Visitors 
 Services 
 General 
 
 History of CNLS 
 
 Maps, Directions 
 CNLS Office 
 T-Division 
 LANL 
 
Thursday, August 25, 2016
10:00 AM - 11:00 AM
CNLS Conference Room (TA-3, Bldg 1690)

Seminar

Quantum Monte Carlo Analysis of Linearly Dispersing Spinons at Deconfined Quantum-Critical Point

Hidemaro Suwa
Department of Physics, The University of Tokyo

Most continuous phase transitions are described by the Landau-Ginzburg-Wilson (LGW) paradigm where an effective action is expanded in powers of an order parameter and its derivatives. For more than a decade, the deconfined quantum criticality has caught a great deal of attention as a highly non-trivial phase-transition point beyond the LGW paradigm. The low-energy (or long-length-scale) physics will be described not by the original degrees of freedom manifest in the model Hamiltonian but by an internal degrees of freedom emerging as fractional excitation. The existence or the stability of such a deconfined quantum-critical point has been debated for the Neel to the valence-bond-solid transition in the two-dimensional quantum spin systems, the three-dimensional non-compact CP$^{N-1}$ action, the loop, and the dimer models. We have studied the excitation energy around the deconfined quantum-critical point in the two-dimensional quantum spin system, the SU(2) J-Q model, by means of the unbiased worldline quantum Monte Carlo method. The energy gaps are estimated by the generalized moment method capturing the asymptotic behavior of the imaginary-time correlation. The transition point is located by the level spectroscopy using the lowest gaps. We find strong quantitative evidence for deconfined linearly dispersing spinons with multiple gapless points at ${\bf k}=(0,0)$, $(\pi,0)$, $(0,\pi)$, and $(\pi,\pi)$, as inferred from two-spinon excitations (S=0 and S=1 states) around these points. We also observe a duality between singlet and triplet excitations at the critical point and inside the ordered phases, in support of an enhanced symmetry, possibly SO(5).

Host: Kipton Barros