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UID:DSC-22119
DTSTART;TZID=Europe/Berlin:20250801T140000
SEQUENCE:1754026535
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URL:https://dresden-science-calendar.org/calendar/en/detail/22119
LOCATION:IFW\, Helmholtzstraße 2001069 Dresden
SUMMARY:Pradenas: Effective Field Theories of Frustrated Antiferromagnets: 
 Helical Edge Modes and Spontaneous Chiral Symmetry Breaking in the Heisenb
 erg Triangular Antiferromagnet
CLASS:PUBLIC
DESCRIPTION:Speaker: Dr. Bastian  Pradenas \nInstitute of Speaker: Johns Ho
 pkins University\, Baltimore\nTopics:\n\n Location:\n  Name: IFW (Zoom: ht
 tps://zoom.us/j/94332095609?pwd=8M2F8tqLrHPojKbA2nXh8qPPK6xDvG.1\, ID: 943
  3209 5609\, CODE: 348651)\n  Street: Helmholtzstraße 20\n  City: 01069 D
 resden\n  Phone: \n  Fax: \nDescription: . We investigate the emergence of
  helical edge modes and new quantum numbers in a Heisenberg antiferromagne
 t on a triangular lattice\, uncovering novel symmetry-driven phenomena in 
 noncollinear spin systems.  Using a spin-frame effective field theory for 
 three-sublattice order\, we demonstrate that the system admits a topologic
 al term in its energy functional which modifies the boundary conditions fo
 r spin waves\, giving rise to helical edge modes - counterpropagating spin
 -wave excitations with opposite circular polarizations—reminiscent of edg
 e states in two-dimensional topological insulators. Notably\, this mechani
 sm requires neither Dzyaloshinskii–Moriya interactions nor nontrivial mag
 non band topology\; rather\, the edge modes are stabilized by a disparity 
 between inequivalent superexchange paths.  In addition\, we identify a pre
 viously overlooked symmetry structure: the spin order parameter transforms
  under an enlarged group\, SO(3)L x SO(2)R\, rather than the conventional 
 spin-rotation group SO(3). Although this extended symmetry is spontaneousl
 y broken by the ground state\, a residual subgroup persists\, giving rise 
 to conserved Noether charges. Upon quantization\, these charges endow magn
 ons with an emergent quantum number—isospin—in addition to energy and mo
 mentum\, drawing unexpected parallels to chiral symmetry breaking in parti
 cle physics.  References:   [1] T. Dombre and N. Read\, Phys. Rev. B 39\, 
 6797 (1989). [2] Bastián Pradenas and Oleg Tchernyshyov\, Phys. Rev. Lett
 . 132\, 096703 (2024). [3] Bastián Pradenas\, Grigor Adamyan\, and Oleg T
 chernyshyov\, Phys. Rev. B 110\, 224426 (2024). [4] Bastián Pradenas\, Gr
 igor Adamyan\, and Oleg Tchernyshyov\, Emergent Isospin from Chiral Symmet
 ry Breaking in Noncollinear Antiferromagnets\, arXiv:2504.12411. [5] Journ
 al Club for Condensed Matter Physics\, May 2025 selection. .
DTSTAMP:20260427T020531Z
CREATED:20250724T053819Z
LAST-MODIFIED:20250801T053535Z
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