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<jats:p>Manipulating the self-assembly of transition metal telluride nanocrystals (NCs) creates opportunities for exploring new properties and device applications. Iron ditelluride (FeTe<jats:sub>2</jats:sub>) has recently emerged as a new class of magnetic semiconductor with three-dimensional (3D) magnetic ordering and narrow band gap structure, yet the self-assembly of FeTe<jats:sub>2</jats:sub> NCs has not been achieved. Herein, the tree-like FeTe<jats:sub>2</jats:sub> nanoarchitectures with orthorhombic crystal structure have been successfully synthesized by hot-injection solvent thermal approach using phosphine-free Te precursor. The morphology, size, and crystal structure have been investigated using transmission electron microscopy (TEM), high-resolution TEM (HRTEM), and powder x-ray diffraction (XRD). We study the formation process of tree-like FeTe<jats:sub>2</jats:sub> NCs according to trace the change of the sample morphology with the reaction time. It was found that the FeTe<jats:sub>2</jats:sub> nanoparticles show oriented aggregation and self-assembly behavior with the increase of reaction time, which is attributed to size-dependent magnetism properties of the samples. The magnetic interaction is thought to be the driving force of nanoparticle self-organization.</jats:p>

<jats:p>We experimentally and theoretically observe the expansion behaviors of a spherical Bose–Einstein condensate. A rubidium condensate is produced in an isotropic optical dipole trap with an asphericity of 0.037. We measure the variation of the condensate size in the expansion process after switching off the trap. The free expansion of the condensate is isotropic, which is different from that of the condensate usually produced in the anisotropic trap. We derive an analytic solution of the expansion behavior based on the spherical symmetry, allowing a quantitative comparison with the experimental measurement. The interaction energy of the condensate is gradually converted into the kinetic energy during the expansion and after a long time the kinetic energy saturates at a constant value. We obtain the interaction energy of the condensate in the trap by probing the long-time expansion velocity, which agrees with the theoretical calculation. This work paves a way to explore novel quantum states of ultracold gases with the spherical symmetry.</jats:p>

<jats:p>We study magnetic and Mott transitions of the Hubbard model on the geometrically frustrated anisotropic checkerboard lattice at half filling using cellular dynamical mean-field theory. Phase diagrams over a wide area of the parameter space are obtained by varying the interparticle interaction strength, geometric frustration strength, and temperature. Our results show that frustration and thermal fluctuations play a competing role against the interactions and in general favor a metallic phase without antiferromagnetic order. Due to their interplay, the system exhibits competition between antiferromagnetic insulator, antiferromagnetic metal, paramagnetic insulator, and paramagnetic metal phases in the intermediate-interaction regime. In the strong-interaction limit, which reduces to the Heisenberg model, our result is consistent with previous studies.</jats:p>

<jats:p>Hydrogen-rich compounds are promising candidates for high-<jats:italic>T</jats:italic> <jats:sub>c</jats:sub> or even room-temperature superconductors. The search for high-<jats:italic>T</jats:italic> <jats:sub>c</jats:sub> hydrides poses a major experimental challenge because there are many known hydrides and even more unknown hydrides with unusual stoichiometries under high pressure. The combination of crystal structure prediction and first-principles calculations has played an important role in the search for high-<jats:italic>T</jats:italic> <jats:sub>c</jats:sub> hydrides, especially in guiding experimental synthesis. Crystal structure AnaLYsis by Particle Swarm Optimization (CALYPSO) is one of the most efficient methods for predicting stable or metastable structures from the chemical composition alone. This review summarizes the superconducting hydrides predicted using CALYPSO. We focus on two breakthroughs toward room-temperature superconductors initiated by CALYPSO: the prediction of high-<jats:italic>T</jats:italic> <jats:sub>c</jats:sub> superconductivity in compressed hydrogen sulfide and lanthanum hydrides, both of which have been confirmed experimentally and have set new record <jats:italic>T</jats:italic> <jats:sub>c</jats:sub> values. We also address the challenges and outlook in this field.</jats:p>

<jats:p>We investigate the negative transconductance effect in p-GaN gate AlGaN/GaN high-electron-mobility transistor (HEMT) associated with traps in the unintentionally doped GaN buffer layer. We find that a negative transconductance effect occurs with increasing the trap concentration and capture cross section when calculating transfer characteristics. The electron tunneling through AlGaN barrier and the reduced electric field discrepancy between drain side and gate side induced by traps are reasonably explained by analyzing the band diagrams, output characteristics, and the electric field strength of the channel of the devices under different trap concentrations and capture cross sections.</jats:p>

<jats:p>In recent years, structure design and predictions based on global optimization approach as implemented in CALYPSO software have gained great success in accelerating the discovery of novel two-dimensional (2D) materials. Here we highlight some most recent research progress on the prediction of novel 2D structures, involving elements, metal-free and metal-containing compounds using CALYPSO package. Particular emphasis will be given to those 2D materials that exhibit unique electronic and magnetic properties with great potentials for applications in novel electronics, optoelectronics, magnetronics, spintronics, and photovoltaics. Finally, we also comment on the challenges and perspectives for future discovery of multi-functional 2D materials.</jats:p>

<jats:p>Atomically thin transition metal dichalcogenide films with distorted trigonal (<jats:inline-formula> <jats:tex-math><?CDATA $1{{\rm{T}}}^{{\prime} }$?></jats:tex-math> <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mn>1</mml:mn> <mml:msup> <mml:mrow> <mml:mi mathvariant="normal">T</mml:mi> </mml:mrow> <mml:mrow> <mml:mo>′</mml:mo> </mml:mrow> </mml:msup> </mml:math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="cpb_28_10_107307_ieqn3.gif" xlink:type="simple" /> </jats:inline-formula>) phase have been predicted to be candidates for realizing quantum spin Hall effect. Growth of <jats:inline-formula> <jats:tex-math><?CDATA $1{{\rm{T}}}^{{\prime} }$?></jats:tex-math> <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mn>1</mml:mn> <mml:msup> <mml:mrow> <mml:mi mathvariant="normal">T</mml:mi> </mml:mrow> <mml:mrow> <mml:mo>′</mml:mo> </mml:mrow> </mml:msup> </mml:math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="cpb_28_10_107307_ieqn4.gif" xlink:type="simple" /> </jats:inline-formula> film and experimental investigation of its electronic structure are critical. Here we report the electronic structure of <jats:inline-formula> <jats:tex-math><?CDATA $1{{\rm{T}}}^{{\prime} }$?></jats:tex-math> <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mn>1</mml:mn> <mml:msup> <mml:mrow> <mml:mi mathvariant="normal">T</mml:mi> </mml:mrow> <mml:mrow> <mml:mo>′</mml:mo> </mml:mrow> </mml:msup> </mml:math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="cpb_28_10_107307_ieqn5.gif" xlink:type="simple" /> </jats:inline-formula>-MoTe<jats:sub>2</jats:sub> films grown by molecular beam epitaxy (MBE). Growth of the <jats:inline-formula> <jats:tex-math><?CDATA $1{{\rm{T}}}^{{\prime} }$?></jats:tex-math> <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mn>1</mml:mn> <mml:msup> <mml:mrow> <mml:mi mathvariant="normal">T</mml:mi> </mml:mrow> <mml:mrow> <mml:mo>′</mml:mo> </mml:mrow> </mml:msup> </mml:math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="cpb_28_10_107307_ieqn6.gif" xlink:type="simple" /> </jats:inline-formula>-MoTe<jats:sub>2</jats:sub> film depends critically on the substrate temperature, and successful growth of the film is indicated by streaky stripes in the reflection high energy electron diffraction (RHEED) and sharp diffraction spots in the low energy electron diffraction (LEED). Angle-resolved photoemission spectroscopy (ARPES) measurements reveal a metallic behavior in the as-grown film with an overlap between the conduction and valence bands. First principles calculation suggests that a suitable tensile strain along the <jats:italic>a</jats:italic>-axis direction is needed to induce a gap to make it an insulator. Our work not only reports the electronic structure of MBE grown <jats:inline-formula> <jats:tex-math><?CDATA $1{{\rm{T}}}^{{\prime} }$?></jats:tex-math> <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mn>1</mml:mn> <mml:msup> <mml:mrow> <mml:mi mathvariant="normal">T</mml:mi> </mml:mrow> <mml:mrow> <mml:mo>′</mml:mo> </mml:mrow> </mml:msup> </mml:math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="cpb_28_10_107307_ieqn7.gif" xlink:type="simple" /> </jats:inline-formula>-MoTe<jats:sub>2</jats:sub> films, but also provides insights for strain engineering to make it possible for quantum spin Hall effect.</jats:p>

<jats:p>We report robust superconducting state and gap symmetry of Nb<jats:sub>5</jats:sub>Ir<jats:sub>3</jats:sub>O via electrical transport and specific heat measurements. The analysis of specific heat manifests that Nb<jats:sub>5</jats:sub>Ir<jats:sub>3</jats:sub>O is a strongly coupled superconductor with <jats:inline-formula> <jats:tex-math><?CDATA ${\rm{\Delta }}C/{\gamma }_{{\rm{n}}}{T}_{{\rm{c}}}\sim 1.91$?></jats:tex-math> <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mi mathvariant="normal">Δ</mml:mi> <mml:mi>C</mml:mi> <mml:mrow> <mml:mo stretchy="false">/</mml:mo> </mml:mrow> <mml:msub> <mml:mrow> <mml:mi>γ</mml:mi> </mml:mrow> <mml:mrow> <mml:mi mathvariant="normal">n</mml:mi> </mml:mrow> </mml:msub> <mml:msub> <mml:mrow> <mml:mi>T</mml:mi> </mml:mrow> <mml:mrow> <mml:mi mathvariant="normal">c</mml:mi> </mml:mrow> </mml:msub> <mml:mo>∼</mml:mo> <mml:mn>1.91</mml:mn> </mml:math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="cpb_28_10_107401_ieqn1.gif" xlink:type="simple" /> </jats:inline-formula> and double s-wave superconducting gaps of <jats:inline-formula> <jats:tex-math><?CDATA $2{{\rm{\Delta }}}_{{\rm{L}}}(0)/{k}_{{\rm{B}}}{T}_{{\rm{c}}}\sim 6.56$?></jats:tex-math> <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mn>2</mml:mn> <mml:msub> <mml:mrow> <mml:mi mathvariant="normal">Δ</mml:mi> </mml:mrow> <mml:mrow> <mml:mi mathvariant="normal">L</mml:mi> </mml:mrow> </mml:msub> <mml:mo stretchy="false">(</mml:mo> <mml:mn>0</mml:mn> <mml:mo stretchy="false">)</mml:mo> <mml:mrow> <mml:mo stretchy="false">/</mml:mo> </mml:mrow> <mml:msub> <mml:mrow> <mml:mi>k</mml:mi> </mml:mrow> <mml:mrow> <mml:mi mathvariant="normal">B</mml:mi> </mml:mrow> </mml:msub> <mml:msub> <mml:mrow> <mml:mi>T</mml:mi> </mml:mrow> <mml:mrow> <mml:mi mathvariant="normal">c</mml:mi> </mml:mrow> </mml:msub> <mml:mo>∼</mml:mo> <mml:mn>6.56</mml:mn> </mml:math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="cpb_28_10_107401_ieqn2.gif" xlink:type="simple" /> </jats:inline-formula> and <jats:inline-formula> <jats:tex-math><?CDATA $2{{\rm{\Delta }}}_{{\rm{S}}}(0)/{k}_{{\rm{B}}}{T}_{{\rm{c}}}\sim 2.36$?></jats:tex-math> <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mn>2</mml:mn> <mml:msub> <mml:mrow> <mml:mi mathvariant="normal">Δ</mml:mi> </mml:mrow> <mml:mrow> <mml:mi mathvariant="normal">S</mml:mi> </mml:mrow> </mml:msub> <mml:mo stretchy="false">(</mml:mo> <mml:mn>0</mml:mn> <mml:mo stretchy="false">)</mml:mo> <mml:mrow> <mml:mo stretchy="false">/</mml:mo> </mml:mrow> <mml:msub> <mml:mrow> <mml:mi>k</mml:mi> </mml:mrow> <mml:mrow> <mml:mi mathvariant="normal">B</mml:mi> </mml:mrow> </mml:msub> <mml:msub> <mml:mrow> <mml:mi>T</mml:mi> </mml:mrow> <mml:mrow> <mml:mi mathvariant="normal">c</mml:mi> </mml:mrow> </mml:msub> <mml:mo>∼</mml:mo> <mml:mn>2.36</mml:mn> </mml:math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="cpb_28_10_107401_ieqn3.gif" xlink:type="simple" /> </jats:inline-formula> accounting for 90% and 10%, respectively. The <jats:inline-formula> <jats:tex-math><?CDATA $({C}_{{\rm{p}}}-{\gamma }_{{\rm{n}}}T)/{T}^{3}$?></jats:tex-math> <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mo stretchy="false">(</mml:mo> <mml:msub> <mml:mrow> <mml:mi>C</mml:mi> </mml:mrow> <mml:mrow> <mml:mi mathvariant="normal">p</mml:mi> </mml:mrow> </mml:msub> <mml:mo>−</mml:mo> <mml:msub> <mml:mrow> <mml:mi>γ</mml:mi> </mml:mrow> <mml:mrow> <mml:mi mathvariant="normal">n</mml:mi> </mml:mrow> </mml:msub> <mml:mi>T</mml:mi> <mml:mo stretchy="false">)</mml:mo> <mml:mrow> <mml:mo stretchy="false">/</mml:mo> </mml:mrow> <mml:msup> <mml:mrow> <mml:mi>T</mml:mi> </mml:mrow> <mml:mrow> <mml:mn>3</mml:mn> </mml:mrow> </mml:msup> </mml:math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="cpb_28_10_107401_ieqn4.gif" xlink:type="simple" /> </jats:inline-formula> vs. <jats:italic>T</jats:italic> plot shows a broad peak at ∼23 K, indicating phonon softening and the appearance of low-lying phonon mode associated with the interstitial oxygen. This behavior explains the monotonic increase of <jats:italic>T</jats:italic> <jats:sub>c</jats:sub> in <jats:inline-formula> <jats:tex-math><?CDATA ${\mathrm{Nb}}_{5}{\mathrm{Ir}}_{3}{{\rm{O}}}_{(1-\delta )}$?></jats:tex-math> <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:msub> <mml:mrow> <mml:mi>Nb</mml:mi> </mml:mrow> <mml:mrow> <mml:mn>5</mml:mn> </mml:mrow> </mml:msub> <mml:msub> <mml:mrow> <mml:mi>Ir</mml:mi> </mml:mrow> <mml:mrow> <mml:mn>3</mml:mn> </mml:mrow> </mml:msub> <mml:msub> <mml:mrow> <mml:mi mathvariant="normal">O</mml:mi> </mml:mrow> <mml:mrow> <mml:mo stretchy="false">(</mml:mo> <mml:mn>1</mml:mn> <mml:mo>−</mml:mo> <mml:mi>δ</mml:mi> <mml:mo stretchy="false">)</mml:mo> </mml:mrow> </mml:msub> </mml:math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="cpb_28_10_107401_ieqn5.gif" xlink:type="simple" /> </jats:inline-formula> by strengthening the electron–phonon coupling and enlarging the density of states at Fermi level. The Hall coefficient is temperature independent below 200 K, and changes its sign from positive to negative above 250 K, suggesting that carrier is across the hole- to electron-dominant regions and the multi-band electronic structures. On warming, the resistivity shows a gradual crossover from <jats:inline-formula> <jats:tex-math><?CDATA ${T}^{2}$?></jats:tex-math> <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:msup> <mml:mrow> <mml:mi>T</mml:mi> </mml:mrow> <mml:mrow> <mml:mn>2</mml:mn> </mml:mrow> </mml:msup> </mml:math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="cpb_28_10_107401_ieqn6.gif" xlink:type="simple" /> </jats:inline-formula>- to <jats:inline-formula> <jats:tex-math><?CDATA ${T}^{3}$?></jats:tex-math> <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:msup> <mml:mrow> <mml:mi>T</mml:mi> </mml:mrow> <mml:mrow> <mml:mn>3</mml:mn> </mml:mrow> </mml:msup> </mml:math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="cpb_28_10_107401_ieqn7.gif" xlink:type="simple" /> </jats:inline-formula>-dependence at a critical temperature <jats:inline-formula> <jats:tex-math><?CDATA ${T}^{* }$?></jats:tex-math> <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:msup> <mml:mrow> <mml:mi>T</mml:mi> </mml:mrow> <mml:mrow> <mml:mo>*</mml:mo> </mml:mrow> </mml:msup> </mml:math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="cpb_28_10_107401_ieqn8.gif" xlink:type="simple" /> </jats:inline-formula>, and a broad peak at a temperature <jats:italic>T</jats:italic> <jats:sub>p</jats:sub>. The reduced <jats:italic>T</jats:italic> <jats:sub>c</jats:sub> under pressure is linearly correlated with lattice parameters <jats:italic>c</jats:italic>/<jats:italic>a</jats:italic> ratio and <jats:italic>T</jats:italic> <jats:sub>p</jats:sub>, suggesting the important phonon contributions in Nb<jats:sub>5</jats:sub>Ir<jats:sub>3</jats:sub>O as a phonon-medicated superconductor. Possible physical mechanisms are proposed.</jats:p>

<jats:p>Micromagnetic simulation is employed to study the gyration motion of magnetic vortices in distinct permalloy nanodisks driven by a spin-polarized current. The critical current density for magnetic vortex gyration, eigenfrequency, trajectory, velocity and the time for a magnetic vortex to obtain the steady gyration are analyzed. Simulation results reveal that the magnetic vortices in larger and thinner nanodisks can achieve a lower-frequency gyration at a lower current density in a shorter time. However, the magnetic vortices in thicker nanodisks need a higher current density and longer time to attain steady gyration but with a higher eigenfrequency. We also find that the point-contact position exerts different influences on these parameters in different nanodisks, which contributes to the control of the magnetic vortex gyration. The conclusions of this paper can serve as a theoretical basis for designing nano-oscillators and microwave frequency modulators.</jats:p>

<jats:p>We propose a cascaded plasmonic nanorod antenna for large broadband electric near-field enhancement. The structure has one big gold nanorod on each side of a small two-wire antenna which consists of two small gold nanorods. For each small nanorod, the enhanced and broadened optical response can be obtained due to the efficient energy transfer from its adjacent big nanorod through strong plasmonic near-field coupling. Thus, the electric field intensity of the cascaded antenna is significantly larger and broader than that of the individual small two-wire antenna. The resonant position, field intensity enhancement, and spectral width of the cascaded antenna are highly tunable by varying the geometry of the system. The quantum efficiency of the cascaded antenna is also greatly enhanced compared with that of the small antenna. Our results are important for the applications in field-enhanced spectroscopy.</jats:p>