Phonon anharmonicity in exfoliated black arsenic flakes

Black arsenic (b-As) with extreme in-plane anisotropy, incredible ambient stability, and excellent transport performance has unlimited potential for device applications. Uncovering phonon–phonon (ph–ph) interactions is a critical step in understanding its transport, especially thermal transport properties. Here, we report on the phonon anharmonicity in an exfoliated b-As flake using temperature-dependent polarized Raman spectroscopy from 80 to 300 K. Polarization of A g 2 mode helps identifying the crystalline orientation of the flake. A nonlinear redshift of peak frequencies of A g 1, B 2 g, and A g 2 modes is observed along the given crystalline orientation. Contributions from intrinsic ph–ph interactions are extracted: cubic-phonon decay dominates the ph–ph scattering processes at low temperature, while cubic- and quartic-phonon decays together do at high temperature. It is further confirmed by the nonlinear full-width-at-half-maxima broadening. Our findings disclose the phonon anharmonicity in b-As and give insight for better understanding and utilizing its thermodynamic properties.