Department of Physics pres.
CM-AMO Seminar | Double Feature - Observation of a Ferro-Rotational Order Coupled with Second-Order Nonlinear Optical Fields & Information Scrambling in Quantum Phases
Elizabeth Drueke (U-M Physics) & Ceren Dag (U-M Physics)
Observation of a Ferro-rotational Order Coupled with Second-order Nonlinear Optical Fields
In this talk, I will discuss our recent discovery of ferrorotational order in RbFe(MoO4)2. Classified by an order parameter which is an axial vector invariant under both time-reversal and spatial-inversion operations, this order is closely related to a number of phenomena such as polar vortices, giant magnetoelectric coupling and spin-helicity-driven ferroelectricity, but it has received little attention so far. Here, using high-sensitivity rotational-anisotropy second-harmonic generation, we have exploited the electric quadrupole contribution to the second harmonic generation to directly couple to this centrosymmetric ferro-rotational order in an archetype of type-II multiferroics, RbFe(MoO4)2. We found that two domain states with opposite ferro-rotational vectors emerge with distinct populations at the critical temperature Tc ≈ 195 K and gradually evolve to reach an even ratio at lower temperatures. Moreover, we have identified the ferro-rotational order phase transition as weakly first order and have revealed its coupling field as a unique combination of the induced electric quadrupole second-harmonic generation and the incident fundamental electric fields.
Information Scrambling in Quantum Phases
Out-of-time-order correlators (OTOCs) are well-established tools for studying quantum chaos in quantum many-body systems as well as information properties of black holes. They characterize the information scrambling which is a dynamical phenomenon where both spatial and temporal correlations spread across a many-body system. Recently an unexpected relation between symmetry-breaking quantum phase transitions and information scrambling has been numerically observed. We introduce a new theoretical tool to understand the reasons and the mechanism of this relation, which makes the dynamical detection of long-range ordered quantum phases via OTOCs intuitive. Based on the studies in literature and our numerical results in the XXZ model, our method renders the relation between information scrambling and quantum phase transitions universal.
Speaker Information: Ceren B. Dag is a graduate student in the Physics Department at the University of Michigan Ann Arbor. She works towards her PhD thesis with Kai Sun and Luming Duan.
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