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TT: Fachverband Tiefe Temperaturen
TT 84: Focus Session: Emerging Magnetic Phenomena from Chiral Phonons II (joint session MA/TT)
TT 84.8: Talk
Friday, March 22, 2024, 11:15–11:30, H 1058
Nuclear boost to pseudomagnetic fields from quantum geometry — •Lennart Klebl1, Arne Schobert1, Giorgio Sangiovanni2, Alexander V. Balatsky3,4, and Tim O. Wehling1,5 — 1Universität Hamburg, Germany — 2Universität Würzburg, Germany — 3University of Connecticut, Storrs, USA — 4Nordita, Stockholm University and KTH Royal Institute of Technology, Stockholm, Sweden — 5The Hamburg Centre for Ultrafast Imaging, Germany
Recent experiments demonstrate precise control over coherently excited phonon modes using high-intensity terahertz lasers, opening new pathways towards dynamical, ultrafast design of magnetism in functional materials. While in qualitative agreement with the observed dynamics in experiments, the theoretically predicted magnetic field strengths of circularly polarized phonon modes lack three orders of magnitude. In this work, we put forward a coupling mechanism based on electron-nuclear quantum geometry. This effect is rooted in the adiabatic evolution of the electronic wavefunction under a circular evolution of nuclear coordinates. The excitation pulse then induces a transient level splitting between electron orbitals that carry angular momentum. When converted to effective magnetic fields, values on the order of tens of Teslas are easily reached. We give criteria under which the evolution of nuclear degrees of freedom can be described adiabatically in the electronic sector and find that in the perovskite SrTiO3, the adiabatic regime is in experimental reach.
Keywords: quantum geometry; berry phase; pseudomagnetic fields