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Total scattering based atomic pair distribution function (PDF) analysis, with the advent of high data throughput neutron powder diffractometers, helps understanding the nature of the Jahn-Teller (JT) phase transition in La 1-x Ca x MnO 3 colossal magnetoresistive (CMR) manganites. The JT distortion of the MnO 6 octahedra, is long-range ordered in the orthorhombic (O) phase, but disappears in the pseudo-cubic (O') phase crystallographically. An anomalous unit cell volume contraction occurs at the transition. The PDF study indicates that the distortion persists locally deep in the O' phase, contrary to the crystallographic view. Simultaneously, local structural features observed in PDF at 10.3 Å, sensitive to the oxygen sublattice changes, evolve dramatically across the transition. The same effect is observed irrespective of the way the O-O' phase boundary is crossed: it is seen both in the temperature series data for x=0, and in the doping series data at 310 K and at 550 K.

Symmetry plays a central role in conventional and topological phases of matter, making the ability to optically drive symmetry changes a critical step in developing future technologies that rely on such control. Topological materials, like the newly discovered topological semimetals, are particularly sensitive to a breaking or restoring of time-reversal and crystalline symmetries, which affect both bulk and surface electronic states. While previous studies have focused on controlling symmetry via coupling to the crystal lattice, we demonstrate here an all-electronic mechanism based on photocurrent generation. Using second-harmonic generation spectroscopy as a sensitive probe of symmetry changes, we observe an ultrafast breaking of time-reversal and spatial symmetries following femtosecond optical excitation in the prototypical type-I Weyl semimetal TaAs. Our results show that optically driven photocurrents can be tailored to explicitly break electronic symmetry in a generic fashion, opening up the possibility of driving phase transitions between symmetry protected states on ultrafast time scales.