Fig. 3: X-ray microscopy.
From: Nanoscale self-organization and metastable non-thermal metallicity in Mott insulators
a Experimental setup. X-rays bunches with tunable energy resonant with the vanadium L2,3 edge impinge on the sample at ~75∘ incidence. The X-ray linear polarization can be rotated from in-plane (Horizontal) to out-of-plane (Vertical). The electrons emitted from the sample are collected and imaged through electrostatic lenses. In the time-resolved configuration, the signal originated by isolated X-rays pulses with linear horizontal (LH) polarization is collected by suitable synchronized gating of the detection apparatus. The pump infrared laser is synchronized to the synchrotron pulses. b XLD-PEEM images taken at 100 K evidencing striped monoclinic domains characterized by different XLD intensity. The three panels show images taken for different polarization angles of the impinging X-ray pulses. The indicated angle refers to the initial (left panel) polarization, which is taken as reference. The colour scale indicates the amplitude (arb. units) of the PEEM signal. We note the existence of the three distinct domains (red, blue, yellow), namely the three monoclinic twins. The XLD signal, as demonstrated in Supplementary Note 3 (See the Supplementary Material), is minimum (blue scale in the panels) when the electric field (grey arrows on top of the images) is parallel to the monoclinic bm axis, which can be any of the primitive hexagonal vectors, aH, bH or −aH–bH, and maximum when E ⋅ bm = 0. Comparing the theoretical prediction with the data, we infer the three primitive hexagonal vectors shown in the figure, and further conclude that that the interface between two twins is perpendicular to the bm axis of the third domain. c XLD signal as a function of the angle between the X-ray polarization and the sample axis. The pink square, green circle and yellow triangle refer to the positions indicated in (a). Within each domain, the XLD signal displays the expected 180∘ periodicity. When comparing the three distinct domains, the XLD signal shows the predicted 60∘ phase shift.
