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<jats:p>First-principles calculations based on the density functional theory were performed to systematically study the electronic properties of the thin film of antimony in (111) orientation. By considering the spin–orbit interaction, for stoichiometric surface, the topological states keep robust for six-bilayer case, and can be recovered in the three-bilayer film, which are guaranteed by time-reversal symmetry and inverse symmetry. For reduced surface doped by non-magnetic Bi or magnetic Mn atom, localized three-fold symmetric features can be identified. Moreover, band structures show that the non-trivial topological states stand for non-magnetic substitutional Bi atom, while can be eliminated by adsorbed or substitutional magnetic Mn atom.</jats:p>

<jats:p>Based on the density functional theory combined with the nonequilibrium Green function methodology, we have studied the thermally-driven spin-dependent transport properties of a combinational molecular junction consisting of a planar four-coordinate Fe molecule and a 15,16-dinitrile dihydropyrene/cyclophanediene molecule, with single-walled carbon nanotube bridge and electrode. Our results show that the magnetic field and light can effectively regulate the thermally-driven spin-dependent currents. Perfect thermal spin-filtering effect and good thermal switching effect are realized. The results are explained by the Fermi–Dirac distribution function, the spin-resolved transmission spectra, the spatial distribution of molecular projected self-consistent Hamiltonian orbitals, and the spin-resolved current spectra. On the basis of these thermally-driven spin-dependent transport properties, we have further designed three basic thermal spin molecular AND, OR, and NOT gates.</jats:p>

<jats:p>Increasing the phonon scattering center by adding nanoparticles to thermoelectric materials is an effective method of regulating the thermal conductivity. In this study, a series of Ca<jats:sub>3</jats:sub>Co<jats:sub>4</jats:sub>O<jats:sub>9</jats:sub>/<jats:italic>x</jats:italic> wt.% CNTs (<jats:italic>x</jats:italic> = 0, 3, 5, 7, 10) polycrystalline ceramic thermoelectric materials by adding carbon nanotubes (CNTs) were prepared with sol-gel method and cold-pressing sintering technology. The results of x-ray diffraction and field emission scanning electron microscopy show that the materials have a single-phase structure with high orientation and sheet like microstructure. The effect of adding carbon nanotubes to the thermoelectric properties of Ca<jats:sub>3</jats:sub>Co<jats:sub>4</jats:sub>O<jats:sub>9</jats:sub> was systematically measured. The test results of thermoelectric properties show that the addition of carbon nanotubes reduces the electrical conductivity and Seebeck coefficient of the material. Nevertheless, the thermal conductivity of the samples with carbon nanotubes addition is lower than that of the samples without carbon nanotubes. At 625 K, the thermal conductivity of Ca<jats:sub>3</jats:sub>Co<jats:sub>4</jats:sub>O<jats:sub>9</jats:sub>/10 wt.% CNTs sample is reduced to 0.408 W⋅m<jats:sup>−1</jats:sup>⋅K<jats:sup>−1</jats:sup>, which is about 73% lower than that of the original sample. When the three parameters are coupled, the figure of merit of Ca<jats:sub>3</jats:sub>Co<jats:sub>4</jats:sub>O<jats:sub>9</jats:sub>/3 wt.% CNTs sample reaches 0.052, which is 29% higher than that of the original sample. This shows that an appropriate amount of carbon nanotubes addition can reduce the thermal conductivity of Ca<jats:sub>3</jats:sub>Co<jats:sub>4</jats:sub>O<jats:sub>9</jats:sub> ceramic samples and improve their thermoelectric properties.</jats:p>

<jats:p>We investigate the electron retroreflection and the Klein tunneling across a graphene-based n–p–n junction irradiated by linearly polarized off-resonant light with the polarization along the <jats:italic>x</jats:italic> direction. The linearly polarized off-resonant light modifies the band structure of graphene, which leads to the anisotropy of band structure. By adjusting the linearly polarized light and the direction of n–p–n junction simultaneously, the electron retroreflection appears and the anomalous Klein tunneling, the perfect transmission at a nonzero incident angle regardless of the width and height of potential barrier, happens, which arises from the fact that the light-induced anisotropic band structure changes the relation of wavevector and velocity of electron. Our finding provides an alternative and flexible method to modulate electron retroreflection and Klein tunneling.</jats:p>

<jats:p>A lateral insulated gate bipolar transistor (LIGBT) based on silicon-on-insulator (SOI) structure is proposed and investigated. This device features a compound dielectric buried layer (CDBL) and an assistant-depletion trench (ADT). The CDBL is employed to introduce two high electric field peaks that optimize the electric field distributions and that, under the same breakdown voltage (BV) condition, allow the CDBL to acquire a drift region of shorter length and a smaller number of stored carriers. Reducing their numbers helps in fast-switching. Furthermore, the ADT contributes to the rapid extraction of the stored carriers from the drift region as well as the formation of an additional heat-flow channel. The simulation results show that the BV of the proposed LIGBT is increased by 113% compared with the conventional SOI LIGBT of the same length <jats:italic>L</jats:italic> <jats:sub>D</jats:sub>. Contrastingly, the length of the drift region of the proposed device (11.2 μm) is about one third that of a traditional device (33 μm) with the same BV of 141 V. Therefore, the turn-off loss (<jats:italic>E</jats:italic> <jats:sub>OFF</jats:sub>) of the CDBL SOI LIGBT is decreased by 88.7% compared with a conventional SOI LIGBT when the forward voltage drop (<jats:italic>V</jats:italic> <jats:sub>F</jats:sub>) is 1.64 V. Moreover, the short-circuit failure time of the proposed device is 45% longer than that of the conventional SOI LIGBT. Therefor, the proposed CDBL SOI LIGBT exhibits a better <jats:italic>V</jats:italic> <jats:sub>F</jats:sub>–<jats:italic>E</jats:italic> <jats:sub>OFF</jats:sub> tradeoff and an improved short-circuit robustness.</jats:p>

<jats:p>Epitaxial Mn<jats:sub>4</jats:sub>N films with different thicknesses were fabricated by facing-target reactive sputtering and their anomalous Hall effect (AHE) is investigated systematically. The Hall resistivity shows a reversed magnetic hysteresis loop with the magnetic field. The magnitude of the anomalous Hall resistivity sharply decreases with decreasing temperature from 300 K to 150 K. The AHE scaling law in Mn<jats:sub>4</jats:sub>N films is influenced by the temperature-dependent magnetization, carrier concentration and interfacial scattering. Different scaling laws are used to distinguish the various contributions of AHE mechanisms. The scaling exponent <jats:italic>γ</jats:italic> &gt; 2 for the conventional scaling in Mn<jats:sub>4</jats:sub>N films could be attributed to the residual resistivity <jats:italic>ρ</jats:italic> <jats:sub> <jats:italic>xx</jats:italic>0</jats:sub>. The longitudinal conductivity <jats:italic>σ<jats:sub>xx</jats:sub> </jats:italic> falls into the dirty regime. The scaling of <jats:inline-formula> <jats:tex-math> <?CDATA ${\rho }_{{\rm{AH}}}=\alpha {\rho }_{xx0}+b{\rho }_{xx}^{n}$?> </jats:tex-math> <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mrow> <mml:msub> <mml:mi>ρ</mml:mi> <mml:mrow> <mml:mi mathvariant="normal">AH</mml:mi> </mml:mrow> </mml:msub> <mml:mo>=</mml:mo> <mml:mi>α</mml:mi> <mml:msub> <mml:mi>ρ</mml:mi> <mml:mrow> <mml:mi>x</mml:mi> <mml:mi>x</mml:mi> <mml:mn>0</mml:mn> </mml:mrow> </mml:msub> <mml:mo>+</mml:mo> <mml:mi>b</mml:mi> <mml:msubsup> <mml:mi>ρ</mml:mi> <mml:mrow> <mml:mi>x</mml:mi> <mml:mi>x</mml:mi> </mml:mrow> <mml:mi>n</mml:mi> </mml:msubsup> </mml:mrow> </mml:math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="cpb_31_4_047305_ieqn1.gif" xlink:type="simple" /> </jats:inline-formula> is used to separate out the temperature-independent <jats:italic>ρ</jats:italic> <jats:sub> <jats:italic>xx</jats:italic>0</jats:sub> from extrinsic contribution. Moreover, the relationship between <jats:italic>ρ</jats:italic> <jats:sub>AH</jats:sub> and <jats:italic>ρ<jats:sub>xx</jats:sub> </jats:italic> is fitted by the proper scaling to clarify the contributions from extrinsic and intrinsic mechanisms of AHE, which demonstrates that the dominant mechanism of AHE in the Mn<jats:sub>4</jats:sub>N films can be ascribed to the competition between skew scattering, side jump and the intrinsic mechanisms.</jats:p>

<jats:p>We report a facile phase conversion method that can locally convert n-type SnSe<jats:sub>2</jats:sub> into p-type SnSe by direct laser irradiation. Raman spectra of SnSe<jats:sub>2</jats:sub> flakes before and after laser irradiation confirm the phase conversion of SnSe<jats:sub>2</jats:sub> to SnSe. By performing the laser irradiation on SnSe<jats:sub>2</jats:sub> flakes at different temperatures, it is found that laser heating effect induces the removal of Se atoms from SnSe<jats:sub>2</jats:sub> and results in the phase conversion of SnSe<jats:sub>2</jats:sub> to SnSe. Lattice-revolved transmission electron microscope images of SnSe<jats:sub>2</jats:sub> flakes before and after laser irradiation further confirm such conversion. By selective laser irradiation on SnSe<jats:sub>2</jats:sub> flakes, a pattern with SnSe<jats:sub>2</jats:sub>/SnSe heteostructures is created. This indicates that the laser induced phase conversion technique has relatively high spatial resolution and enables the creation of micron-sized in-plane p–n junction at predefined region.</jats:p>

<jats:p>Thermoelectric materials have the ability to directly convert heat into electricity, which have been extensively studied for decades to solve global energy shortages and environmental problems. As a medium temperature (400–800 K) thermoelectric material, SnTe has attracted extensive attention as a promising substitute for PbTe due to its non-toxic characteristics. In this paper, the research status of SnTe thermoelectric materials is reviewed, and the strategies to improve its performance are summarized and discussed in terms of electrical and thermal transport properties. This comprehensive discussion will provides guidance and inspiration for the research on SnTe.</jats:p>

<jats:p>The (GeTe)<jats:sub> <jats:italic>x</jats:italic> </jats:sub>(AgSbTe<jats:sub>2</jats:sub>)<jats:sub>100 – <jats:italic>x</jats:italic> </jats:sub> alloys, also called TAGS-<jats:italic>x</jats:italic> in short, have long been demonstrated as a promising candidate for thermoelectric applications with successful services as the p-type leg in radioisotope thermoelectric generators for space missions. This largely stems from the complex band structure for a superior electronic performance and strong anharmonicity for a low lattice thermal conductivity. Utilization of the proven strategies including carrier concentration optimization, band and defects engineering, an extraordinary thermoelectric figure of merit, <jats:italic>zT</jats:italic>, has been achieved in TAGS-based alloys. Here, crystal structure, band structure, microstructure, synthesis techniques and thermoelectric transport properties of TAGS-based alloys, as well as successful strategies for manipulating the thermoelectric performance, are surveyed with opportunities for further advancements. These strategies involved are believed to be in principle applicable for advancing many other thermoelectrics.</jats:p>

<jats:p>Magnetic susceptibility, specific heat, and neutron powder diffraction measurements have been performed on polycrystalline Li<jats:sub>2</jats:sub>Co(WO<jats:sub>4</jats:sub>)<jats:sub>2</jats:sub> samples. Under zero magnetic field, two successive magnetic transitions at <jats:italic>T</jats:italic> <jats:sub>N1</jats:sub> ∼ 9.4 K and <jats:italic>T</jats:italic> <jats:sub>N2</jats:sub> ∼ 7.4 K are observed. The magnetic ordering temperatures gradually decrease as the magnetic field increases. Neutron diffraction reveals that Li<jats:sub>2</jats:sub>Co(WO<jats:sub>4</jats:sub>)<jats:sub>2</jats:sub> enters an incommensurate magnetic state with a temperature dependent <jats:italic> <jats:bold>k</jats:bold> </jats:italic> between <jats:italic>T</jats:italic> <jats:sub>N1</jats:sub> and <jats:italic>T</jats:italic> <jats:sub>N2</jats:sub>. The magnetic propagation vector locks-in to a commensurate value <jats:italic> <jats:bold>k</jats:bold> </jats:italic> = (1/2, 1/4, 1/4) below <jats:italic>T</jats:italic> <jats:sub>N2</jats:sub>. The antiferromagnetic structure is refined at 1.7 K with Co<jats:sup>2+</jats:sup> magnetic moment 2.8(1) <jats:italic>μ</jats:italic> <jats:sub>B</jats:sub>, consistent with our first-principles calculations.</jats:p>