Berlin 2024 – wissenschaftliches Programm
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TT: Fachverband Tiefe Temperaturen
TT 87: Frustrated Magnets: Spin Liquids
TT 87.11: Vortrag
Freitag, 22. März 2024, 12:15–12:30, H 3010
Spin-Peierls instability of deconfined quantum critical points — •David Hofmeier1, Josef Willsher1,2, Urban Seifert3, and Johannes Knolle1,2,4 — 1TU Munich, Germany — 2MCQST, Germany — 3Kavli Institute, UCSB, USA — 4Imperial College London, UK
Deconfined quantum critical points (DQCPs) are possible phase transitions beyond the Landau paradigm. The original example of a DQCP is the spin-1/2 quantum antiferromagnet on the square lattice which features a second order transition between valence bond solid (VBS) and Néel order. The VBS order breaks a lattice symmetry which should naturally lead to a coupling between phonons and the VBS order parameter. We investigate a field-theoretic description of the DQCP in the presence of a monopole-lattice coupling. We show that treating phonons as classical lattice distortions leads to a relevant monopole-phonon interaction inducing an instability towards the plaquette VBS phase. Consequently, there is a breakdown of the DQCP which generally becomes a first-order transition. Taking into account the full quantum nature of the phonons may alleviate this, where we argue that the DQCP persists above a critical phonon frequency. This work provides an extension of the spin-Peierls instability of algebraic spin liquid phases to a beyond-Landau phase transition, a fact we justify by close analogy with the 1D analogs of deconfined criticality. We discuss the implications of our findings to recent experiments on the Shastry--Sutherland lattice, and indeed argue that this spin-lattice coupling can be used to explain the observed plaquette order.
Keywords: Deconfined Quantum Criticality; Spin-Phonon Coupling; Fractionalization