Abstract
The electronic structure and functionality of 2D materials is highly sensitive to structural morphology, not only opening the possibility for manipulating material properties but also making predictable and reproducible functionality challenging. Black phosphorus (BP), a corrugated orthorhombic 2D material, has in-plane optical absorption anisotropy critical for applications, such as directional photonics, plasmonics, and waveguides. Here, we use polarization-dependent photoemission electron microscopy to visualize the anisotropic optical absorption of BP with 54 nm spatial resolution. We find the edges of BP flakes have a shift in their optical polarization anisotropy from the flake interior due to the 1D confinement and symmetry reduction at flake edges that alter the electronic charge distributions and transition dipole moments of edge electronic states, confirmed with first-principles calculations. These results uncover previously hidden modification of the polarization-dependent absorbance at the edges of BP, highlighting the opportunity for selective excitation of edge states of 2D materials with polarized light.
Original language | English |
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Pages (from-to) | 3180-3186 |
Number of pages | 7 |
Journal | Nano Letters |
Volume | 22 |
Issue number | 8 |
DOIs | |
State | Published - Apr 27 2022 |
Funding
This work was funded by the Office of Basic Energy Sciences, U.S. Department of Energy (Grant No. DE-SC0021950). This work was partially supported by the University of Chicago Materials Research Science and Engineering Center, which is funded by the National Science Foundation under award number DMR-2011854 and DMR-1420709; this work made use of the shared facilities at the University of Chicago Materials Research Science and Engineering Center, supported by National Science Foundation under award number DMR-2011854. P.P.J. acknowledges support from a MRSEC-funded Kadanoff-Rice fellowship (DMR-2011854 and DMR-1420709). S.B.K. acknowledges start-up funding support from the University of Chicago and the Neubauer Family Assistant Professors Program. Theoretical calculations were conducted by L.L. at the Center for Nanophase Materials Sciences, which is a Department of Energy Office of Science User Facility. L.L. used resources of the Compute and Data Environment for Science (CADES) at the Oak Ridge National Laboratory, which is supported by the Office of Science of the U.S. Department of Energy under Contract No. DE-AC05-00OR22725.
Keywords
- 2D materials
- anisotropic material
- black phosphorus
- edge electronic states