Catálogo de publicaciones - revistas

<jats:p> <jats:italic>Based on density functional theory calculations, it is found that for substitutional N in diamond the <jats:italic>C</jats:italic> <jats:sub>3<jats:italic>v</jats:italic> </jats:sub> symmetry structure is more stable, while <jats:italic>C</jats:italic> <jats:sub>3<jats:italic>v</jats:italic> </jats:sub> and <jats:italic>D</jats:italic> <jats:sub>2<jats:italic>d</jats:italic> </jats:sub> symmetry patterns for the substitutional P in diamond have comparable energies. Moreover, the substitutional N is a deep donor for diamond, while P is a shallow substitutional n-type dopant. This is attributed to the different doping positions of dopant (the N atom is seriously deviated from the substitutional position, while the P atom nearly locates in the substitutional site), which are determined by the atomic radius.</jats:italic> </jats:p>

<jats:p> <jats:italic>Molecular dynamics simulations are performed to investigate the effects of low-energy recoils on the microscopic structure of porous silica. Exhibiting a logistic growth with the recoil energy, the displacement probability of Si is shown to be smaller than that of O at the same primary knock-on level. Computations of pair distribution functions and bond angle distributions reveal that this material upon irradiation with energies around the displacement thresholds mainly undergoes structural changes in the medium-range order. In the porous network, while the formation of nonbridging oxygen defects tends to induce shorter Si–O bonds than those formed by bridging oxygen atoms, a remarkable increase of inter-tetrahedral bond angles created by multiple recoils can be observed and associated with the rearrangement of ring statistics.</jats:italic> </jats:p>

<jats:p> <jats:italic>The key to fully understanding water-solid interfaces relies on the microscopic nature of hydrogen bond networks, including their atomic structures, interfacial interactions, and dynamic behaviors. Here, we report the observation of two types of simplest water chains on Au(111) surface which is expected unstable according to the rules of hydrogen network on noble metal surfaces. A common feature at the end of chain structures is revealed in high resolution scanning tunneling microscopy images. To explain the stability in observed hydrogen bond networks, we propose a structure model of the water chains terminated with a hydroxyl group. The model is consistent with detailed image analysis and molecular manipulation. The observation of simplest water chains suggests a new platform for exploring fundamental physics in hydrogen bond networks on surfaces.</jats:italic> </jats:p>

<jats:p> <jats:italic>The topological edge states of two-dimensional topological insulators with large energy gaps furnish ideal conduction channels for dissipationless current transport. Transition metal tellurides <jats:italic>X</jats:italic>Te<jats:sub>5</jats:sub> (<jats:italic>X</jats:italic>=Zr, Hf) are theoretically predicted to be large-gap two-dimensional topological insulators, and the experimental observations of their bulk insulating gap and in-gap edge states have been reported, but the topological nature of these edge states still remains to be further elucidated. Here, we report our low-temperature scanning tunneling microscopy/spectroscopy study on single crystals of HfTe<jats:sub>5</jats:sub>. We demonstrate a full energy gap of ∼80 meV near the Fermi level on the surface monolayer of HfTe<jats:sub>5</jats:sub> and that such an insulating energy gap gets filled with finite energy states when measured at the monolayer step edges. Remarkably, such states are absent at the edges of a narrow monolayer strip of one-unit-cell in width but persist at both step edges of a unit-cell wide monolayer groove. These experimental observations strongly indicate that the edge states of HfTe<jats:sub>5</jats:sub> monolayers are not trivially caused by translational symmetry breaking, instead they are topological in nature protected by the 2D nontrivial bulk properties.</jats:italic> </jats:p>

<jats:p> <jats:italic>Systematic theoretical calculations are performed to investigate the dopant effect of Fe on stability, electronic and magnetic properties of the newly synthesized all-boron fullerene B<jats:sub>40</jats:sub>. The results reveal that as a typical ferromagnetic element, Fe atoms can either be chemically externally adsorbed on, or internally encapsulated in the cage of B<jats:sub>40</jats:sub>, with the binding energies ranging from 3.07 to 5.31 eV/atom. By introducing the dopant states from the doped Fe atom, the energy gaps of the Fe-doped B<jats:sub>40</jats:sub>-based metallofullerenes are decreased. Our spin-polarized calculations indicate that Fe-doped metallofullerenes have attractive magnetic properties: with alternative binary magnetic moments between 4.00<jats:italic>μ</jats:italic> <jats:sub> <jats:sub>B</jats:sub> </jats:sub> and 2.00<jats:italic>μ</jats:italic> <jats:sub> <jats:sub>B</jats:sub> </jats:sub>, depending on the resident sites of the doped Fe atom. The findings of the tunable electronic properties and binary magnetic moments of the Fe-doped B<jats:sub>40</jats:sub>-based metallofullerenes imply that this type of metallofullerene may be applied in single molecular devices.</jats:italic> </jats:p>

<jats:p> <jats:italic>Nodal line semimetal (NLS) is a new quantum state hosting one-dimensional closed loops formed by the crossing of two bands. The so-called type-II NLS means that these two crossing bands have the same sign in their slopes along the radial direction of the loop, which requires that the crossing bands are either right-tilted or left-tilted at the same time. According to the theoretical prediction, Mg<jats:sub>3</jats:sub>Bi<jats:sub>2</jats:sub> is an ideal candidate for studying the type-II NLS by tuning its spin-orbit coupling (SOC). High-quality Mg<jats:sub>3</jats:sub>Bi<jats:sub>2</jats:sub> films are grown by molecular beam epitaxy (MBE). By <jats:italic>in-situ</jats:italic> angle resolved photoemission spectroscopy (ARPES), a pair of surface resonance bands around the <jats:inline-formula> <jats:tex-math><?CDATA $\bar{\varGamma }$?></jats:tex-math> <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mrow> <mml:mover accent="true"> <mml:mi>Γ</mml:mi> <mml:mo stretchy="false">¯</mml:mo> </mml:mover> </mml:mrow> </mml:math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="cpl_36_11_117303_ieqn1.gif" xlink:type="simple" /> </jats:inline-formula> point are clearly seen. This shows that Mg<jats:sub>3</jats:sub>Bi<jats:sub>2</jats:sub> films grown by MBE are Mg(1)-terminated by comparing the ARPES spectra with the first principles calculations results. Moreover, the temperature dependent weak anti-localization effect in Mg<jats:sub>3</jats:sub>Bi<jats:sub>2</jats:sub> films is observed under magneto-transport measurements, which shows clear two-dimensional (2D) <jats:italic>e</jats:italic>–<jats:italic>e</jats:italic> scattering characteristics by fitting with the Hikami–Larkin–Nagaoka model. Therefore, by combining with ARPES, magneto-transport measurements and the first principles calculations, this work proves that Mg<jats:sub>3</jats:sub>Bi<jats:sub>2</jats:sub> is a semimetal with topological surface states. This paves the way for Mg<jats:sub>3</jats:sub>Bi<jats:sub>2</jats:sub> to be used as an ideal material platform to study the exotic features of type-II nodal line semimetals and the topological phase transition by tuning its SOC.</jats:italic> </jats:p>

<jats:p> <jats:italic>High-quality epitaxial LaRhO<jats:sub>3</jats:sub> (LRO) thin films on SrTiO<jats:sub>3</jats:sub> (110) single-crystalline substrates are fabricated by pulsed laser deposition and their photoconductivity properties are studied. The transient photoconductivity (TPC) effect is found in this semiconductor LRO film at room temperature. The magnitude of TPC increases almost linearly with the laser power intensities and the photon energies in visible light range. Moreover, the difference in the TPC results under two airflow conditions confirms that both intrinsic photoinduced carrier accumulation and extrinsic photoinduced heating effects contribute to the magnitude of TPC effect.</jats:italic> </jats:p>

<jats:p> <jats:italic>We study the transport property of single C<jats:sub>60</jats:sub> molecular transistors with special focus on the situation that other molecules are in vicinity. The devices are prepared using electromigration and thermal deposition techniques. Pure single C<jats:sub>60</jats:sub> molecule transistors show typical coulomb blockade behavior at low temperature. When we increase the coverage of molecules slightly by extending the deposition time, the transport spectrum of devices displays a switching behavior in the general coulomb blockade pattern. We attribute this unconventional phenomenon to the influence from a nearby C<jats:sub>60</jats:sub> molecule. By analyzing this transport behavior quantitatively based on the parallel-double-quantum-dot model, the interaction from the nearby molecule is proved to be of capacity and tunneling coupling. Thermal stimulation is also applied to the device to investigate the effect of local charging environment variation on intermolecular interaction</jats:italic>.</jats:p>

<jats:p> <jats:italic>Solitonic characteristics are revealed in the diffusion process of a hump or a notch wave packet in a one-dimensional Bose–Einstein condensate. By numerically solving the time-dependent Gross–Pitaevskii equation, we find completely different spreading behavior for attractive or repulsive condensates. For the attractive condensate, a series of bright solitons are continuously generated one after another at the wave front and they nearly stay at the positions where they are generated in the whole diffusion process. In contrast, for the repulsive condensate, the initial wave packet splits at the beginning into a series of grey solitons that travel at different velocities. The moving velocity of the grey soliton depends on nonlinear interaction strength, as well as the shape of a particular grey soliton</jats:italic>.</jats:p>

<jats:p> <jats:italic>We propose a new exponential shape function in wormhole geometry within modified gravity. The energy conditions and the equation-of-state parameter are obtained. The radial and tangential null energy conditions, and also the weak energy condition are validated, which indicates the absence of exotic matter due to modified gravity allied with such a new proposal.</jats:italic> </jats:p>