Dresden 2026 – scientific programme
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TT: Fachverband Tiefe Temperaturen
TT 2: Quantum-Critical Phenomena (joint session TT/DY)
TT 2.3: Talk
Monday, March 9, 2026, 10:00–10:15, HSZ/0101
Stability of Deconfined Quantum Critical Points Coupled to Quantum Phonons — •Anton Romen1,2, Josef Willsher1,2,3, David Hofmeier4, Johannes Knolle1,2,5, and Michael Knap1,2 — 1Technical University of Munich, Garching, Germany — 2Munich Center for Quantum Science and Technology, München, Germany — 3Max-Planck-Institut für Physik komplexer Systeme, Dresden, Germany — 4University of Southern Denmark, Odense M, Denmark — 5Imperial College London, London, United Kingdom
Deconfined quantum criticality (DQC) describes continuous transitions beyond the Landau-Ginzburg paradigm. A typical example is the VBS-Néel transition in frustrated antiferromagnets. Since the VBS order parameter breaks lattice symmetries, it can couple to lattice distortions (phonons). Field-theory (PRB 110, 125130 (2024)) predicts that static lattice vibrations induce strong first-order character. A full quantum treatment, however, indicates that DQC survives above a critical phonon frequency. In this work, we provide a detailed study on the stability of 1D DQC under spin-phonon coupling resorting to a frustrated anisotropic J1-J2 model as a paradigmatic example. Using large-scale tensor network simulations, we determine the flow of the continuously varying critical exponents with phonon frequency and the critical phonon frequency, at which the transition becomes strongly first-order. By relating the critical theory to an Ashkin-Teller type model, we argue that the critical endpoint is in the four-state Potts universality class. We further compute dynamical phonon spectral functions that provide a powerful experimental signature of DQC.
Keywords: Deconfined Quantum Criticality; Spin-Phonon Coupling; Frustrated Magnets; Ashkin-Teller Physics