title: Emergence of Two-Dimensional Massless Dirac Fermions, Chiral Pseudospins, and Berry's Phase in Potassium Doped Few-Layer Black Phosphorus.
abstract: Thin flakes of black phosphorus (BP) are a two-dimensional (2D) semiconductor whose energy gap is predicted being sensitive to the number of layers and external perturbations. Very recently, it was found that a simple method of potassium (K) doping on the surface of BP closes its band gap completely, producing a Dirac semimetal state with a linear band dispersion in the armchair direction and a quadratic one in the zigzag direction. Here, based on first-principles density functional calculations, we predict that, beyond the critical K density of the gap closure, 2D massless Dirac Fermions (i.e., Dirac cones) emerge in K-doped few-layer BP, with linear band dispersions in all momentum directions, and the electronic states around Dirac points have chiral pseudospins and Berry's phase. These features are robust with respect to the spin-orbit interaction and may lead to graphene-like electronic transport properties with greater flexibility for potential device applications.
authors.affiliation: Department of Physics, Yonsei University , Seoul 120-749, Korea.|Center for Computational Studies of Advanced Electronic Material Properties, Yonsei University , Seoul 120-749, Korea.
authors.forename: Seung Su
authors.initials: SS
authors.lastname: Baik
authors.affiliation: Department of Physics, Pohang University of Science and Technology , Pohang 790-784, Korea.|Center for Artificial Low Dimensional Electronic Systems, Institute for Basic Science , Pohang 790-784, Korea.
authors.forename: Keun Su
authors.initials: KS
authors.lastname: Kim
authors.affiliation: Department of Physics, Yonsei University , Seoul 120-749, Korea.
authors.forename: Yeonjin
authors.initials: Y
authors.lastname: Yi
authors.affiliation: Department of Physics, Yonsei University , Seoul 120-749, Korea.|Center for Computational Studies of Advanced Electronic Material Properties, Yonsei University , Seoul 120-749, Korea.
authors.forename: Hyoung Joon
authors.initials: HJ
authors.lastname: Choi
keywords: Berry’s phase; Black phosphorus; chiral pseudospins; massless Dirac Fermions; potassium doping