Angle-resolved photoemission with circularly polarized light in the nodal mirror plane of underdoped Bi2Sr2CaCu2O8+ δ superconductor

Unraveling the nature ofpseudogap phase inhigh-temperature superconductors holds the key to understanding their superconducting mechanisms and potentially broadening their applications via enhancement of their superconducting transitiontemperatures. Angle-resolvedphotoemission spectroscopy (ARPES) experiments using circularly polarized light have been proposed to detect possible symmetry breaking state in thepseudogap phase of cuprates. The presence (absence) of an electronic order which breaksmirror symmetry of the crystal would in principle induce a finite (zero) circulardichroism inphotoemission. Different orders breaking reflection symmetries about differentmirror planes can also be distinguished by the momentum dependence of the measured circulardichroism. Here, we report ARPES experiment on an underdoped Bi2Sr2CaCu2O8+δ (Bi2212)superconductor in the Γ (0,0)-Y (π,π) nodalmirror plane using circularly polarized light. No circulardichroism is observed on the level of ∼2% at low temperature, which places a clear constraint on the forms of possible symmetry breaking orders in this sample. Meanwhile, we find that the geometricdichroism remains substantial very close to its perfect extinction such that a very small sample angular offset is sufficient to induce a sizeable dichroic signal. It highlights the importance to establish a perfect extinction of geometricdichroism as a prerequisite for the identification of any intrinsic circulardichroism in this material.

Source: Applied Physics Letters - November 3, 2016 Category: Physics Authors: Junfeng He, Thomas R. Mion, Shang Gao, Gavin T. Myers, Masashi Arita, Kenya Shimada, G. D. Gu and Rui-Hua He Source Type: research