Fig. 2
From: Strain-tunable van der Waals interactions in few-layer black phosphorus
Comparison of the biaxial strain effects on 3L and 4L BP. a Optical image of the adjacent 3L and 4L BP flakes. Scale bar: 20 μm. b IR extinction spectra for the 3L and 4L BP under different biaxial strains. Dashed lines are guides to the eye. c Transition energies of E11 in the 3L and 4L BP as a function of biaxial strain. The solid lines are linear fits to the data. The inset shows E11 energy difference of 3L and 4L BP as a function of biaxial strain. Dots are experiment data averaged from heating and cooling processes and the solid lines are linear fits which give shift rates of 158 and 185 meV/% for 3L and 4L, respectively
