Regensburg 2025 – wissenschaftliches Programm
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DY: Fachverband Dynamik und Statistische Physik
DY 30: Quantum-Critical Phenomena (joint session TT/DY)
DY 30.4: Vortrag
Donnerstag, 20. März 2025, 10:15–10:30, H31
Interplay of nematic fluctuations and transverse phonons near a nematic quantum critical point — •Morten H. Christensen1, Michael Schütt2, Avraham Klein3, and Rafael M. Fernandes4 — 1Niels Bohr Institute, University of Copenhagen — 2University of Minnesota — 3Ariel University — 4University of Illinois Urbana-Champaign
In an electronic fluid absent an atomic lattice, an electronic nematic transition can be described as a consequence of a Pomeranchuk instability of the Fermi surface with an associated critical nematic mode. As a coupling to an atomic lattice is introduced, the nematic transition is accompanied by a structural distortion of the lattice. Here, we study the fluctuation spectra near such a coupled nematic-structural transition driven primarily by the electronic nematic fluctuations. This requires coupling the nematic fluctuations to transverse phonons which implies that the transition is no longer accompanied by a critical nematic mode, but rather by the vanishing of the transverse phonon velocity along a certain direction. To understand how, e.g., superconductivity is affected by this, knowledge of the dynamic behaviour of the hybrid nematic/phonon soft excitation is crucial. The purpose of this presentation is to elucidate the properties of this mode. We find that the low-energy fluctuations are generally overdamped except near the soft lattice directions where they become underdamped. How the transition from overdamped to underdamped takes place depends on the proximity to the nematic quantum critical point.
Keywords: Electronic nematicity; Transverse phonons; Structural transitions