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<jats:p>Nanostructuring, structure distortion, and/or disorder are the main manipulation techniques to reduce the lattice thermal conductivity and improve the figure of merit of thermoelectric materials. A single-phase <jats:italic>α</jats:italic>-MgAgSb sample, MgAg<jats:sub>0.97</jats:sub>Sb<jats:sub>0.99</jats:sub>, with high thermoelectric performance in near room temperature region was synthesized through a high-energy ball milling with a hot-pressing method. Here, we report the average grain size of 24–28 nm and the accurate structure distortion, which are characterized by high-resolution neutron diffraction and synchrotron x-ray diffraction with Rietveld refinement data analysis. Both the small grain size and the structure distortion have a contribution to the low lattice thermal conductivity in MgAg<jats:sub>0.97</jats:sub>Sb<jats:sub>0.99</jats:sub>.</jats:p>

<jats:p>By applying nonequilibrium Green’s functions in combination with the density-functional theory, we investigate the electronic, thermal, and thermoelectric properties of four kinds of bases in DNA perpendicularly coupling between two ZGNR electrodes. The results show that the electron transport is highly sensitive to different base-ZGNR coupling geometries, and the system can present large rectifying and negative differential resistance effects. Moreover, the fluctuations of electronic transmission and super-low thermal conductance result in significant enhancement of the thermoelectric figure of merit (<jats:italic>ZT</jats:italic>): the <jats:italic>ZT</jats:italic> will be over 1.4 at room temperature, and over 1.6 at 200 K. The results show that the base-ZGNR coupling devices can present large rectifying, negative differential resistance, and enhanced thermoelectric effects.</jats:p>

<jats:p>The nontrivial topology is investigated in a dodecagonal quasicrystal made of 30° twisted bilayer graphene (TBG). Based on tight-binding model with both exchange field and Rashba spin–orbit coupling, the topological index, chiral edge states, and quantum conductance are calculated to distinguish its unique topological phase. A high Bott index (<jats:italic>B</jats:italic> = 4) quantum anomalous Hall effect (QAHE) is identified in TBG quasicrystal, which is robust to a finite perturbation without closing the nontrivial gap. Most remarkably, we have found that the multiple Dirac cone replicas in TBG quasicrystal are only a spectra feature without generating extra chiral edge states. Our results not only propose a possible way to realize the QAHE in quasicrystal, but also identify the continuity of nontrivial topology in TBG between crystal and quasicrystal.</jats:p>

<jats:p>Stress voltages on time-dependent breakdown characteristics of GaN MIS-HEMTs during negative gate bias stress (with <jats:italic>V</jats:italic> <jats:sub>GS</jats:sub> &lt; 0, <jats:italic>V</jats:italic> <jats:sub>D</jats:sub> = <jats:italic>V</jats:italic> <jats:sub>S</jats:sub> = 0) and off-state stress (<jats:italic>V</jats:italic> <jats:sub>G</jats:sub> &lt; <jats:italic>V</jats:italic> <jats:sub>Th</jats:sub>, <jats:italic>V</jats:italic> <jats:sub>DS</jats:sub> &gt; 0, <jats:italic>V</jats:italic> <jats:sub>S</jats:sub> = 0) are investigated. For negative bias stress, the breakdown time distribution (<jats:italic>β</jats:italic>) decreases with the increasing negative gate voltage, while <jats:italic>β</jats:italic> is larger for higher drain voltage at off-state stress. Two humps in the time-dependent gate leakage occurred under both breakdown conditions, which can be ascribed to the dielectric breakdown triggered earlier and followed by the GaN layer breakdown. Combining the electric distribution from simulation and long-term monitoring of electric parameter, the peak electric fields under the gate edges at source and drain sides are confirmed as the main formation locations for per-location paths during negative gate voltage stress and off-state stress, respectively.</jats:p>

<jats:p>Trapping effect in normally-off Al<jats:sub>2</jats:sub>O<jats:sub>3</jats:sub>/AlGaN/GaN metal–oxide–semiconductor (MOS) high-electron-mobility transistors (MOS-HEMTs) with post-etch surface treatment was studied in this paper. Diffusion-controlled interface oxidation treatment and wet etch process were adopted to improve the interface quality of MOS-HEMTs. With capacitance–voltage (<jats:italic>C</jats:italic>–<jats:italic>V</jats:italic>) measurement, the density of interface and border traps were calculated to be 1.13 × 10<jats:sup>12</jats:sup> cm<jats:sup>−2</jats:sup> and 6.35 × 10<jats:sup>12</jats:sup> cm<jats:sup>−2</jats:sup>, effectively reduced by 27% and 14% compared to controlled devices, respectively. Furthermore, the state density distribution of border traps with large activation energy was analyzed using photo-assisted <jats:italic>C</jats:italic>–<jats:italic>V</jats:italic> measurement. It is found that irradiation of monochromatic light results in negative shift of <jats:italic>C</jats:italic>–<jats:italic>V</jats:italic> curves, which indicates the electron emission process from border traps. The experimental results reveals that the major border traps have an activation energy about 3.29 eV and the change of post-etch surface treatment process has little effect on this major activation energy.</jats:p>

<jats:p>The strong chiroptical effect is highly desirable and has a wide range of applications in biosensing, chiral catalysis, polarization tuning, and chiral photo detection. In this work, we find a simple method to enhance the reflection circular dichroism (CD<jats:sub>R</jats:sub>) by placing the planar anisotropic chiral metamaterials (i.e., Z-shaped PACMs) on the interface of two media (i.e., Z-PCMI) with a large refractive index difference. The maximum reflection CD<jats:sub>R</jats:sub> from the complex system can reach about 0.840 when the refractive index is set as <jats:italic>n</jats:italic> <jats:sub>top</jats:sub> = 4.0 and <jats:italic>n</jats:italic> <jats:sub>bottom</jats:sub> = 1.49, which is approximately three times larger than that of placing the Z-shaped PACMs directly on the substrate (i.e., Z-PCMS). While the minimum reflection CD<jats:sub>R</jats:sub> is 0.157 when the refractive index is set as <jats:italic>n</jats:italic> <jats:sub>bottom</jats:sub> = 1.49. So we can get a large available range of reflection CD<jats:sub>R</jats:sub> from –0.840 to –0.157. Meanwhile, the transmission CD<jats:sub>T</jats:sub> remains unchanged with the refractive index <jats:italic>n</jats:italic> <jats:sub>top</jats:sub> increment. Our in-depth research indicates that the large reflection CD<jats:sub>R</jats:sub> is derived from the difference of non-conversion components of the planar anisotropic chiral metamaterials’ reflection matrices. In short, we provide a simple and practical method to enhance the chiroptical effect by changing the refractive index difference between two media without having to design a complex chiral structure.</jats:p>

<jats:p>Large threshold voltage and small on-state current are the main limitations of the normal tunneling field effect transistor (TFET). In this paper, a novel TFET with gate-controlled P<jats:sup>+</jats:sup>N<jats:sup>+</jats:sup>N<jats:sup>+</jats:sup> structure based on partially depleted GeOI (PD-GeOI) substrate is proposed. With the buried P<jats:sup>+</jats:sup>-doped layer (BP layer) introduced under P<jats:sup>+</jats:sup>N<jats:sup>+</jats:sup>N<jats:sup>+</jats:sup> structure, the proposed device behaves as a two-tunneling line device and can be shut off by the BP junction, resulting in a high on-state current and low threshold voltage. Simulation results show that the on-state current density <jats:italic>I</jats:italic> <jats:sub>on</jats:sub> of the proposed TFET can be as large as 3.4 × 10<jats:sup>−4</jats:sup> A/μm, and the average subthreshold swing (<jats:italic>SS</jats:italic>) is 55 mV/decade. Moreover, both of <jats:italic>I</jats:italic> <jats:sub>on</jats:sub> and SS can be optimized by lengthening channel and buried P<jats:sup>+</jats:sup> layer. The off-state current density of TTP TFET is 4.4 × 10<jats:sup>−10</jats:sup> A/μm, and the threshold voltage is 0.13 V, showing better performance than normal germanium-based TFET. Furthermore, the physics and device design of this novel structure are explored in detail.</jats:p>

<jats:p>Super-high resolution laser-based angle-resolved photoemission measurements are carried out on LiFeAs superconductor to investigate its electron dynamics. Three energy scales at ∼ 20 meV, ∼ 34 meV, and ∼ 55 meV are revealed for the first time in the electron self-energy both in the superconducting state and normal state. The ∼ 20 meV and ∼ 34 meV scales can be attributed to the coupling of electrons with sharp bosonic modes which are most likely phonons. These observations provide definitive evidence on the existence of mode coupling in iron-based superconductors.</jats:p>

<jats:p>A synthetic antiferromagnet based on a thin antiferromagnetically coupled Co<jats:sub>2</jats:sub>MnSi/MnGa bilayer with Pt capping is proposed in this work. Square magnetic loops measured by anomalous Hall effect reveal that a well perpendicular magnetic anisotropy is obtained in this structure. A very large coercivity of 83 kOe (1 Oe = 79.5775 A⋅m<jats:sup>−1</jats:sup>) is observed near the magnetic moment compensation point of 270 K, indicating an antiferromagnetic behavior. Moreover, the anomalous Hall signal does not go to zero even at the magnetic compensation point, for which the difficulty in detecting the conventional antiferromagnets can be overcome. By changing the temperature, the polarity of the spin–orbit torque induced switching is changed around the bilayer compensation point. This kind of thin bilayer has potential applications in spin–orbit-related effects, spintronic devices, and racetrack memories.</jats:p>