Dresden 2026 – wissenschaftliches Programm

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DY: Fachverband Dynamik und Statistische Physik

DY 60: Critical Phenomena and Phase Transitions

DY 60.5: Vortrag

Freitag, 13. März 2026, 10:30–10:45, ZEU/0114

Quadrupoling in ferroic materials — •Finja Tietjen and Richard Matthias Geilhufe — Chalmers University of Technology, Gothenburg, Sweden

Quadrupolar ordering has been investigated and characterized experimentally in different materials in recent years, but the theoretical approaches have only focused on special cases so far. We follow a new approach where we describe the quadrupoling as a composite order, arising from the fluctuations of a parent phase. This is in contrast to the conventional approach, where different phases are regarded as competing. We derive a mesoscopic field theory that includes thermal fluctuations. That enables us to find the anisotropy-dependent transition temperature and the free energy of the quadrupolar phase. We identify the phase transition into the quadrupolar phase as first-order and show that it is linked to a tetragonal distortion of the lattice of the material. With this framework, we correctly predict experimental measurements of the distortion in Ba2MgReO6 upon entering its quadrupole phase [1].

[1] D. Hirai, H. Sagayama, S. Gao, H. Ohsumi, G. Chen, T.-h. Arima, and Z. Hiroi, 'Detection of multipolar orders in the spin-orbit-coupled 5d Mott insulator Ba2MgReO6', Physical Review Research 2, 022063 (2020)

Keywords: quadrupole; ferroic; phase transition; field theory; strain