Valley Pseudospin with a Widely Tunable Bandgap in Doped Honeycomb BN Monolayer

Abstract

Valleytronics is a promising paradigm to explore the emergent degree of freedom for charge carriers on the energy band edges. Using ab initio calculations, we reveal that the honeycomb boron nitride (h-BN) monolayer shows a pair of inequivalent valleys in the vicinities of the vertices of hexagonal Brillouin zone even without the protection of the C symmetry. The inequivalent valleys give rise to a 2-fold degree of freedom named the valley pseudospin. The valley pseudospin with a tunable bandgap from deep ultraviolet to far-infrared spectra can be obtained by doping h-BN monolayer with carbon atoms. For a low-concentration carbon periodically doped h-BN monolayer, the subbands with constant valley Hall conductance are predicted due to the interaction between the artificial superlattice and valleys. In addition, the valley pseudospin can be manipulated by visible light for high-concentration carbon doped h-BN monolayer. In agreement with our calculations, the circularly polarized photoluminescence spectra of the BNC sample show a maximum valley-contrasting circular polarization of 40% and 70% at room temperature and 77 K, respectively. Our work demonstrates a class of valleytronic materials with a controllable bandgap.

Hexagonal BN‐Assisted Epitaxy of Strain Released GaN Films for True Green Light‐Emitting Diodes

“…[41][42][43] At the same time, these surface defects can adsorb hydroxide ions in the HCl solution, forming two kinds of oxygen-related defects, B-O and B-O-N bonds. [44][45][46] Figure S4, Supporting Information). This also indicates that the proposed atomic configurations at the interface are reasonable.…”

Epitaxial Single‐Layer MoS2 on GaN with Enhanced Valley Helicity

“…However, the optically generated valley polarization, especially at room temperature, is much smaller than the expected value from first‐principles calculations . While many attempts have been made to improve the valley helicity, such as modulating the sample quality, measuring at low temperature, and pumping with a near‐resonant excitation, the effect of substrate engineering has not been explored thoroughly. The 2D material–substrate interactions can strongly influence the valley polarization through strain, electron–electron and electron–phonon interactions, etc.…”

Recent Advances in Quantum Effects of 2D Materials

“…The abundant members in the 2D layered materials family afford versatile opportunities and open innovative perspectives for exploring fundamental science and nanodevice applications covering the fields of electronics, photonics, optoelectronics, spintronics, and valleytronics . In this review, we summarized the impressive quantum effects recently discovered in representative 2DLMs, which are caused by quantum behaviors of the 2D electrons from three main perspectives, that is, the evolution of electronic band structure, electronic polarization, and electronic transport.…”