Electron-Hole Asymmetry in the Electron-phonon Coupling in Top-gated   Phosphorene Transistor
  Using in-situ Raman scattering from phosphorene channel in an electrochemically top-gated field effect transistor, we show that its phonons with A$_g$ symmetry depend much more strongly on concentration of electrons than that of holes, while the phonons with B$_g$ symmetry are insensitive to doping. With first-principles theoretical analysis, we show that the observed electon-hole asymmetry arises from the radically different constitution of its conduction and valence bands involving $\pi$ and $\sigma$ bonding states respectively, whose symmetry permits coupling with only the phonons that preserve the lattice symmetry. Thus, Raman spectroscopy is a non-invasive tool for measuring electron concentration in phosphorene-based nanoelectronic devices. 
Biswanath Chakraborty, Satyendra Nath Gupta, Anjali Singh, Manabendra   Kuiri, Chandan Kumar, D. V. S. Muthu, Anindya Das, U...
cond-mat.mes-hall cond-mat.mtrl-sci