Electronic anisotropies revealed by detwinned angle-resolved photo-emission spectroscopy measurements of FeSe
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چکیده
We report high resolution angle-resolved photo-emission spectroscopy (ARPES)measurements of detwinned FeSe single crystals. The application of amechanical strain is used to promote the volume fraction of one of the orthorhombic domains in the sample, whichwe estimate to be 80% detwinned. While the full structure of the electron pockets consisting of two crossed ellipsesmay be observed in the tetragonal phase at temperatures above 90K,wefind that remarkably, only one peanut-shaped electron pocket oriented along the longer a axis contributes to the ARPESmeasurement at low temperatures in the nematic phase, with the expected pocket along b being not observed. Thus the low temperature Fermi surface of FeSe as experimentally determined byARPES consists of one elliptical hole pocket and one orthogonally-oriented peanut-shaped electron pocket. Ourmeasurements clarify the long-standing controversies over the interpretation of ARPESmeasurements of FeSe.
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