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Electronic properties of graphene hexagonal boron nitride moiré superlattice  [PDF]
Pilkyung Moon,Mikito Koshino
Physics , 2014, DOI: 10.1103/PhysRevB.90.155406
Abstract: We theoretically investigate the electronic structures of moir\'{e} superlattices arising in monolayer / bilayer graphene stacked on hexagonal boron nitride (hBN) in presence and absence of magnetic field. We develop an effective continuum model from a microscopic tight-binding lattice Hamiltonian, and calculate the electronic structures of graphene-hBN systems with different rotation angles. Using the effective model, we explain the characteristic band properties such as the gap opening at the corners of the superlattice Brillouin zone (mini-Dirac point). We also investigate the energy spectrum and quantum Hall effect of graphene-hBN systems in uniform magnetic field and demonstrate the evolution of the fractal spectrum as a function of the magnetic field. The spectrum generally splits in the valley degrees of freedom ($K$ and $K'$) due to the lack of the inversion symmetry, and the valley splitting is more significant in bilayer graphene on hBN than in monolayer graphene on hBN because of the stronger inversion-symmetry breaking in bilayer.
Quasi free-standing silicene in a superlattice with hexagonal boron nitride  [PDF]
T. P. Kaloni,M. Tahir,U. Schwingenschl?gl
Physics , 2013, DOI: 10.1038/srep03192
Abstract: We study a superlattice of silicene and hexagonal boron nitride by first principles calculations and demonstrate that the interaction between the layers of the superlattice is very small. As a consequence, quasi free-standing silicene is realized in this superlattice. In particular, the Dirac cone of silicene is preserved, which has not been possible in any other system so far. Due to the wide band gap of hexagonal boron nitride, the superlattice realizes the characteristic physical phenomena of free-standing silicene. In particular, we address by model calculations the combined effect of the intrinsic spin-orbit coupling and an external electric field, which induces a transition from a metal to a topological insulator and further to a band insulator.
Moire superlattice effects in graphene/boron-nitride van der Waals heterostructures  [PDF]
J. R. Wallbank,M. Mucha-Kruczynski,Xi Chen,V. I. Fal'ko
Physics , 2014, DOI: 10.1002/andp.201400204
Abstract: Van der Waals heterostructures of graphene and hexagonal boron nitride feature a moir\'e superlattice for graphene's Dirac electrons. Here, we review the effects generated by this superlattice, including a specific miniband structure featuring gaps and secondary Dirac points, and a fractal spectrum of magnetic minibands known as Hofstadter's butterfly.
Valley Order and Loop Currents in Graphene on Hexagonal Boron Nitride  [PDF]
Bruno Uchoa,Valeri N. Kotov,M. Kindermann
Physics , 2014, DOI: 10.1103/PhysRevB.91.121412
Abstract: In this letter, we examine the role of Coulomb interactions in the emergence of macroscopically ordered states in graphene supported on hexagonal boron nitride substrates. Due to incommensuration effects with the substrate, graphene can develop gapped low energy modes that spatially conform into a triangular superlattice of quantum rings. In the presence of these modes, we show that Coulomb interactions lead to spontaneous formation of chiral loop currents in bulk and to macroscopic spin-valley order at zero temperature. We show that this exotic state breaks time reversal symmetry and can be detected with interferometry and polar Kerr measurements.
Superlattice Based on Graphene on a Strip Substrate  [PDF]
P. V. Ratnikov
Physics , 2012, DOI: 10.1134/S0021364009180143
Abstract: A graphene-based superlattice formed due to the periodic modulation of the band gap has been investigated. Such a modulation is possible in graphene deposited on a strip substrate made of silicon oxide and hexagonal boron nitride. The advantages and some possible problems in the superlattice under consideration are discussed. A model describing such a superlattice is proposed and the dispersion relation between the energy and momentum of carriers has been obtained using the transfer matrix method within this model.
Graphene on Hexagonal Boron Nitride  [PDF]
Matthew Yankowitz,Jiamin Xue,Brian J. LeRoy
Physics , 2014, DOI: 10.1088/0953-8984/26/30/303201
Abstract: The field of graphene research has developed rapidly since its first isolation by mechanical exfoliation in 2004. Due to the relativistic Dirac nature of its charge carriers, graphene is both a promising material for next-generation electronic devices and a convenient low-energy testbed for intrinsically high-energy physical phenomena. Both of these research branches require the facile fabrication of clean graphene devices so as not to obscure its intrinsic physical properties. Hexagonal boron nitride has emerged as a promising substrate for graphene devices, as it is insulating, atomically flat and provides a clean charge environment for the graphene. Additionally, the interaction between graphene and boron nitride provides a path for the study of new physical phenomena not present in bare graphene devices. This review focuses on recent advancements in the study of graphene on hexagonal boron nitride devices from the perspective of scanning tunneling microscopy with highlights of some important results from electrical transport measurements.
Interband absorption in single layer hexagonal boron nitride  [PDF]
Aniruddha Konar,Raj Jana,Tian Fang,Guowang Li,William O'Brien,Debdeep Jena
Physics , 2011,
Abstract: Monolayer of hexagonal boron nitride (h-BN), commonly known as "white graphene" is a promising wide bandgap semiconducting material for deep-ultaviolet optoelectronic devices. In this report, the light absorption of a single layer hexagonal boron nitride is calculated using a tight-binding Hamiltonian. The absorption is found to be monotonically decreasing function of photon energy compared to graphene where absorption coefficient is independent of photon energy and characterized by the effective fine-structure constant.
Graphene on boron-nitride: Moiré pattern in the van der Waals energy  [PDF]
M. Neek-Amal,F. M. Peeters
Physics , 2014, DOI: 10.1063/1.4863661
Abstract: The spatial dependence of the van der Waals (vdW) energy between graphene and hexagonal boron-nitride (h-BN) is investigated using atomistic simulations. The van der Waals energy between graphene and h-BN shows a hexagonal superlattice structure identical to the observed Moir\'e pattern in the local density of states (LDOS) which depends on the lattice mismatch and misorientation angle between graphene and h-BN. Our results provide atomistic features of the weak van der Waals interaction between graphene and BN which are in agreement with experiment and provide an analytical expression for the size of the spatial variation of the weak van der Waals interaction. We also found that the A-B-lattice symmetry of graphene is broken a long the armchair direction.
Minimum thermal conductance in graphene and boron nitride superlattice  [PDF]
Jin-Wu Jiang,Bing-Shen Wang,Jian-Sheng Wang
Physics , 2011, DOI: 10.1063/1.3619832
Abstract: The minimum thermal conductance versus supercell size ($d_{s}$) is revealed in graphene and boron nitride superlattice with $d_{s}$ far below the phonon mean free path. The minimum value is reached at a constant ratio of $d_{s}/L\approx 5%$, where $L$ is the total length of the superlattice; thus the minimum point of $d_{s}$ depends on $L$. The phenomenon is attributed to the localization property and the number of confined modes in the superlattice. With the increase of $d_{s}$, the localization of the confined mode is enhanced while the number of confined modes decreases, which directly results in the minimum thermal conductance.
High thermal conductivity of hexagonal boron nitride laminates  [PDF]
Jin-Cheng Zheng,Liang Zhang,Andrey V Kretinin,Sergei V Morozov,Yi Bo Wang,Tun Wang,Xiaojun Li,Fei Ren,Jingyu Zhang,Ching-Yu Lu,Jia-Cing Chen,Miao Lu,Hui-Qiong Wang,Andre K Geim,Konstantin S Novoselov
Physics , 2015,
Abstract: Two-dimensional materials are characterised by a number of unique physical properties which can potentially make them useful to a wide diversity of applications. In particular, the large thermal conductivity of graphene and hexagonal boron nitride has already been acknowledged and these materials have been suggested as novel core materials for thermal management in electronics. However, it was not clear if mass produced flakes of hexagonal boron nitride would allow one to achieve an industrially-relevant value of thermal conductivity. Here we demonstrate that laminates of hexagonal boron nitride exhibit thermal conductivity of up to 20 W/mK, which is significantly larger than that currently used in thermal management. We also show that the thermal conductivity of laminates increases with the increasing volumetric mass density, which creates a way of fine-tuning its thermal properties.
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