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DTSTAMP:20260411T014408
DTSTART:20190121T113000
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URL:https://murmitoyen.com/events/vanille/udem/detail/848703-hidden-order-i
 n-the-heisenberg-kitaev-ladder-erik-sorensen-mcmaster
LOCATION:Université de Montréal - Pavillon J.-Armand-Bombardier\, 5155\, 
 chemin de la rampe \, Montréal\, QC\, Canada\, H3T 2B2
SUMMARY:Hidden Order in the Heisenberg-Kitaev Ladder - Erik Sorensen (McMas
 ter)
DESCRIPTION:Hidden Order in the Heisenberg-Kitaev LadderErik SorensenPhysic
 s DepartmentMcMaster University
\nAbstract: String\, or hidden order\, as 
 it arises in quantum spin systems was first shown to exist in S=1 quantum 
 spin chains that have many experimental realizations. Although the ground-
 state in such materials looks like a liquid and has no detectable local or
 der parameter\, a non-local (string-) order parameter can be defined. Prec
 isely how these ideas can be extended to models in higher dimensions and w
 ith spin different from S=1 is not entirely clear and in this talk\, I wil
 l discuss recent work extending the notion of a string order parameter to 
 S=1/2 ladders. In particular\, we study the S=1/2 Kitaev-Heisenberg (KJ) m
 odel in two-leg ladders. The Kitaev-Heisenberg model defined on the two-di
 mensional honeycomb lattice has recently received considerable attention d
 ue to possible experimental realizations and our results show that the two
 -leg ladder very closely models the behavior of the 2D honeycomb lattice. 
 For the Kitaev-Heisenberg ladder\, we prove the existence of a non-local s
 tring order parameter (SOP) in the Kitaev phase which survives with a fini
 te Heisenberg interaction. This differentiates the Kitaev phases from othe
 r nearby phases. Two phases with non-zero SOP corresponding to ferromagnet
 ic and antiferromagnetic Kitaev interactions are identified. The full phas
 e diagram of the KJ model is determined using exact diagonalization and de
 nsity matrix renormalization group methods\, which shows a striking simila
 rity to the KJ model on a two-dimensional honeycomb lattice.
\nTo know mor
 e about Prof. Sorensen\, you can consult his web page at McMaster Universi
 ty.
\nCette conférence est présentée par le RQMP Versant Nord du Dé
 partement de physique de l'Université de Montréal et de Génie physiqu
 e de la Polytechnique.
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