Fluctuations, Emergence, and Dynamics of Topological Supertextures by Design

Fluctuations, Emergence, and Dynamics of Topological Supertextures by DesignV. Gopalan (Penn State, Lead)L. Q. Chen (Penn State),J. W. Freeland (APS, ANL),A. M. Lindenberg (Stanford),L. W. Martin (LBNL/U. C. Berkeley),V. Stoica (Penn State),H. Wen (MSD, ANL).Complexity is ubiquitous in nature, emerging from many-body interactions between elementary building blocks of fundamental fields and particles. At a certain scale of complexity, one observes the 'emergence' of new phenomena such as band structures in solids and life in organic matter. The central focus of this renewal proposal is to study the emergence and dynamics of a rich portfolio of complex topological structures, focusing on testing key hypotheses that address the underlying mechanisms.The ongoing project (DE-SC0012375) was triggered by experimental successes of members of this team in designing polar complexity in (PbTiO3)m/(SrTiO3)noxide superlattices that led to the emergence of supercrystals, polar vortices, and skyrmions. These first-of-their-kind synthetic topological polar structures are collectively dubbedpolar supertextures. They involve structural modulations ranging from sub-angstrom-to-tens of nanometer scales and are created in a succession of stimulated phenomena from femtoseconds to milliseconds. We poise such systems on the verge of instability through competing strain and polarization gradients, drive them with an appropriate impulse (i.e., an ultrafast pulse of light and/or field) and then monitor ultrafast processes using state-of-the-art experiments at synchrotron (e.g., the Advanced Photon Source (APS) and, during the APS upgrade, at NSLS-II and SSRL) and XFEL (e.g., LCLS, SACLA, and PAL-XFEL) facilities. These are complemented with ultrafast optics and atomic and unique computational methods such as dynamical phase field modeling. We will also make full use of the ongoingLCLS Campaign beamtime.The proposal is focused on answering three fundamental questions that form the three proposed thrusts: (1) What are the atomic and mesoscale stochastic processes that are collectively excited along non-equilibrium energy pathways towards the emergence of specific polar supertextures? (2) What role does ultrafast lattice dynamics play in the creation of emergent supertextures? (3) How can we design new heterostructures that exhibit expanded structural and functional couplings?We continue to push the boundaries of instrumentation and methodology, especially on the XFEL front such as single-shot pump probe and single-shot XPCS over six orders of magnitude in time scale. We propose new experiments involving nonlinear coherent phonon pumping regimes, low-temperature THz pump-X-ray probe experiments, write-probe-in-situ erase-rewrite-re-probe schemes for high repetition rate XPCS, a new technique called vibrationally resolved XPCS, and will take advantage of the high energies and repetition rates at the LCLS II. We will disseminate the knowledge broadly and provide inclusive and equitable opportunities for a diverse group of students in a highly interdisciplinary research environment. We will make special efforts to engage underrepresented groups, through recruitment, summer programs and outreach activities.