Catálogo de publicaciones - revistas

<jats:p>The water dimer demonstrates a completely different protype in water systems, it prefers not forming larger clusters instead existing in vapor phase stably, which contracts the viewpoint of the cooperative effect of hydrogen bond (O–H ··· O). It is well accepted that the cooperative effect is beneficial to forming more hydrogen bonds (O–H ··· O), leading to stronger H-bond (H ··· O) and increase in the O–H bond length with contraction of intermolecular distance. Herein, the high-precision <jats:italic>ab initio</jats:italic> methods of calculations applied on water dimer shows that the O–H bond length decreases and H-bond (H ··· O) becomes weaker with decreasing H-bond length and O ··· O distance, which can be considered as the uncooperative effect of hydrogen bond (O–H ··· O). It is ascribed to the exchange repulsion of electrons, which results in decrease of the O–H bond length and prevents the decrease in the O ··· O distance connected with the increasing scale of water clusters. Our findings highlight the uncooperative effect of hydrogen bond attributed to exchange repulsion of electrons as the mechanism for stabilizing water dimer in vapor phase, and open a new perspective for studies of hydrogen-bonded systems.</jats:p>

<jats:p>We present an approach, a Terahertz streaking-assisted photoelectron spectrum (THz SAPS), to achieve direct observations of ultrafast coherence dynamics with timescales beyond the pulse duration. Using a 24 fs probe pulse, the THz SAPS enables us to well visualize Rabi oscillations of 11.76 fs and quantum beats of 2.62 fs between the 5<jats:italic>S</jats:italic> <jats:sub>1/2</jats:sub> and 5<jats:italic>P</jats:italic> <jats:sub>3/2</jats:sub> in rubidium atoms. The numerical results show that the THz SAPS can simultaneously achieve high resolution in both frequency and time domains without the limitation of Heisenberg uncertainty of the probe pulse. The long probe pulse promises sufficiently high frequency resolution in photoelectron spectroscopy allowing to observe Autler–Townes splittings, whereas the streaking THz field enhances temporal resolution for not only Rabi oscillations but also quantum beats between the ground and excited states. The THz SAPS demonstrates a potential applicability for observation and manipulation of ultrafast coherence processes in frequency and time domains.</jats:p>

<jats:p>We study the mechanism of van der Waals (vdW) interactions on phonon transport in atomic scale, which would boost developments in heat management and energy conversion. Commonly, the vdW interactions are regarded as a hindrance in phonon transport. Here we propose that the vdW confinement can enhance phonon transport. Through molecular dynamics simulations, it is realized that the vdW confinement is able to make more than two-fold enhancement on thermal conductivity of both polyethylene single chain and graphene nanoribbon. The quantitative analyses of morphology, local vdW potential energy and dynamical properties are carried out to reveal the underlying physical mechanism. It is found that the confined vdW potential barriers reduce the atomic thermal displacement magnitudes, leading to less phonon scattering and facilitating thermal transport. Our study offers a new strategy to modulate the phonon transport.</jats:p>

<jats:p>Due to the limitations of impedance matching and attenuation matching, carbon nanotubes (CNTs) employed alone have a weak capacity to attenuate electromagnetic wave (EMW) energy. In this work, B and N co-doped CNTs with embedded Ni nanoparticles (Ni@BNCNTs) are fabricated via an <jats:italic>in situ</jats:italic> doping method. Compared with a sample without B doping, Ni@BNCNTs demonstrate a superior EMW absorption performance, with all minimum reflection loss values below −20 dB, even at a matching thickness of 1.5 mm. The experimental and theoretical calculation results demonstrate that B doping increases conduction and polarization relaxation losses, as well as the impedance matching characteristic, which is responsible for the enhanced EMW absorption performance of Ni@BNCNTs.</jats:p>

<jats:p>Recently, the negative differential thermal resistance effect was discovered in a homojunction made of a negative thermal expansion material, which is very promising for realizing macroscopic thermal transistors. Similar to the Monte Carlo phonon simulation to deal with grain boundaries, we introduce positive temperature-dependent interface thermal resistance in the modified Lorentz gas model and find negative differential thermal resistance effect. In the homojunction, we reproduce a pair of equivalent negative differential thermal resistance effects in different temperature gradient directions. In the heterojunction, we realize the unidirectional negative differential thermal resistance effect, and it is accompanied by the super thermal rectification effect. Using this new way to achieve high-performance thermal devices is a new direction, and will provide extensive reference and guidance for designing thermal devices.</jats:p>

<jats:p>We demonstrate strong photonic thermal rectification effect between polar dielectrics plate and the composite metamaterials containing nonspherical polar dielectric nanoparticles with small volume fractions. Thermal rectification efficiency is found to be adjusted by the volume fractions and the nanoparticles' shape, and it can be as large as 80% when the polar dielectric nanoparticles are spherical in shape and are in the dilute limit with the volume fraction <jats:italic>f</jats:italic> = 0.01. Physically, there exists strong electromagnetic coupling between the surface phonon polariton mode of polar dielectrics plate and the localized surface phonon polariton mode around polar dielectric nanoparticles. The results provide alternative new freedom for regulating energy flow and heat rectification efficiency in the near field, and may be helpful for design of multiparameter adjustable thermal diodes.</jats:p>

<jats:p>We report the dynamic crossover behavior in metallic glass nanoparticles (MGNs) with the size reduction based on the extensive molecular dynamics (MD) simulations combined with the activation-relaxation technique (ART). The fragile-to-strong transition of dynamics can be achieved by just modulating the characteristic size of MGNs. It can be attributed to the abnormal fast surface dynamics enhanced by the surface curvature. By determining the potential energy surface, we reveal the hierarchy-to-flat transition of potential energy landscape (PEL) in MGNs, and demonstrate the intrinsic flat potential landscape feature of the MGN with size smaller than a critical size. Our results provide an important piece of the puzzle about the size-modulated potential energy landscape and shed some lights on the unique properties of MGs in nanoscale.</jats:p>

<jats:p>We report a universal transfer methodology for producing artificial heterostructures of large-area freestanding single-crystalline WTe<jats:sub>2</jats:sub> membranes on diverse target substrates. The transferred WTe<jats:sub>2</jats:sub> membranes exhibit a nondestructive structure with a carrier mobility comparable to that of as-grown films (∼ 179–1055 cm<jats:sup>2</jats:sup> · V<jats:sup>−1</jats:sup> · s<jats:sup>−1</jats:sup>). Furthermore, the transferred membranes show distinct Shubnikov–de Haas quantum oscillations as well as weak localization/weak anti-localization. These results provide a new approach to the development of atom manufacturing and devices based on atomic-level, large-area topological quantum films.</jats:p>

<jats:p>We report electronic and magnetic properties of full Heusler Pd<jats:sub>2</jats:sub>TiIn based on first principles calculations. This compound has been variously characterized as magnetic or non-magnetic. We use first principles calculations with accurate methods to reexamine this issue. We find that ideal ordered Heusler Pd<jats:sub>2</jats:sub>TiIn remains non-magnetic, in accord with prior work. However, we do find that it is possible to explain the magnetism seen in experiments through disorder and in particular we find that site disorder can lead to moment formation in this compound. In addition, we find an alternative low energy cubic crystal structure, which will be of interest to explore experimentally.</jats:p>

<jats:p>We report the observation of in-plane anisotropic magnetoresistance and planar Hall effect in non-magnetic HfTe<jats:sub>5</jats:sub> thin layers. The observed anisotropic magnetoresistance as well as its sign is strongly dependent on the critical resistivity anomaly temperature <jats:italic>T</jats:italic> <jats:sub>p</jats:sub>. Below <jats:italic>T</jats:italic> <jats:sub>p</jats:sub>, the anisotropic magnetoresistance is negative with large negative magnetoresistance. When the in-plane magnetic field is perpendicular to the current, the negative longitudinal magnetoresistance reaches its maximum. The negative longitudinal magnetoresistance effect in HfTe<jats:sub>5</jats:sub> thin layers is dramatically different from that induced by the chiral anomaly as observed in Weyl and Dirac semimetals. One potential underlying origin may be attributed to the reduced spin scattering, which arises from the in-plane magnetic field driven coupling between the top and bottom surface states. Our findings provide valuable insights for the anisotropic magnetoresistance effect in topological electronic systems and the device potential of HfTe<jats:sub>5</jats:sub> in spintronics and quantum sensing.</jats:p>