arXiv subjects

Deniz Cakir

Publications and source records attributed to Deniz Cakir.

3 recordsLinked to original sources

arXiv2017

Distinct Correlation between the Vibrational and Thermal Transport Properties of Group \textrm{VA} Monolayer Crystals

The investigation of thermal transport properties of novel two dimensional materials is crucially important in order to assess their potential to be used in future technological applications, such as thermoelectric power generation. In this respect, lattice thermal transport properties of monolayer structures of the group \textrm{VA} elements (P, As, Sb, Bi, PAs, PSb, PBi, AsSb, AsBi, SbBi, P$_{3}$As$_{1}$, P$_{3}$Sb$_{1}$, P$_{1}$As$_{3}$, As$_{3}$Sb$_{1}$) with black phosphorus like puckered structure were systematically investigated by first principles calculations and an iterative solution of the Phonon Boltzmann transport equation. Phosphorene was found to have the highest lattice thermal conductivity, $κ$, due to its low average atomic mass and strong interatomic bonding character. As a matter of course, anisotropic $κ$ were obtained for all the considered materials, owing to anisotropy in phonon group velocities and scattering rates (relaxation times) calculated for these structures. However, the determined linear correlation between the anisotropy in $κ$ of P, As, and Sb is significant. The results corresponding to the studied compound structures clearly point out that thermal (electronic) conductivity of pristine monolayers might be suppressed (improved) by alloying them with the same group elements. For instance, the room temperature $κ$ of PBi along armchair direction was predicted as low as 1.5 Wm$^{-1}$K$^{-1}$, whereas that of P was predicted to be 21 Wm$^{-1}$K$^{-1}$. In spite of the apparent differences in structural and vibrational properties, we peculiarly revealed an intriguing correlation between the $κ$ of all the considered materials as $κ$=c$_{1}$ + c$_{2}$/$m^{2}$, in particular along zigzag direction.

cond-mat.mes-hall↗

arXiv2015

Remarkable effect of stacking on the electronic and optical properties of few layer black phosphorus

The effect of the number of stacking layers and the type of stacking on the electronic and optical properties of bilayer and trilayer black phosphorus are investigated by using first principles calcula- tions within the framework of density functional theory. We find that inclusion of many body effects (i.e., electron-electron and electron-hole interactions) modifies strongly both the electronic and opti- cal properties of black phosphorus. While trilayer black phosphorus with a particular stacking type is found to be a metal by using semilocal functionals, it is predicted to have an electronic band gap of 0.82 eV when many-body effects are taken into account within the G0W0 scheme. Though different stacking types result in similar energetics, the size of the band gap and the optical response of bilayer and trilayer phosphorene is very sensitive to the number of layers and the stacking type. Regardless of the number of layers and the type of stacking, bilayer and trilayer black phosphorus are direct band gap semiconductors whose band gaps vary within a range of 0.3 eV. Stacking arrangments different from the ground state structure in both bilayer and trilayer black phosphorus significantly modify valence bands along the zigzag direction and results in larger hole effective masses. The optical gap of bilayer (trilayer) black phosphorus varies by 0.4 (0.6) eV when changing the stacking type. Due to strong interlayer interaction, some stackings obstruct the observation of the optical excitation of bound excitons within the quasi-particle band gap. In other stackings, the binding energy of bound excitons hardly changes with the type of stacking and is found to be 0.44 (0.30) eV for bilayer (trilayer) phosphorous.

cond-mat.mes-hall↗

arXiv2007

Half-metallic silicon nanowires

From first-principles calculations, we predict that transition metal (TM) atom doped silicon nanowires have a half-metallic ground state. They are insulators for one spin-direction, but show metallic properties for the opposite spin direction. At high coverage of TM atoms, ferromagnetic silicon nanowires become metallic for both spin-directions with high magnetic moment and may have also significant spin-polarization at the Fermi level. The spin-dependent electronic properties can be engineered by changing the type of dopant TM atoms, as well as the diameter of the nanowire. Present results are not only of scientific interest, but can also initiate new research on spintronic applications of silicon nanowires.

cond-mat.mtrl-sci↗