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<jats:p>The N<jats:sub>2</jats:sub>O radicals <jats:italic>in-situ</jats:italic> treatment on gate region has been employed to improve device performance of recessed-gate AlGaN/GaN high-electron-mobility transistors (HEMTs). The samples after gate recess etching were treated by N<jats:sub>2</jats:sub>O radicals without physical bombardment. After <jats:italic>in-situ</jats:italic> treatment (IST) processing, the gate leakage currents decreased by more than one order of magnitude compared to the sample without IST. The fabricated HEMTs with the IST process show a low reverse gate current of 10<jats:sup>−9</jats:sup> A/mm, high on/off current ratio of 10<jats:sup>8</jats:sup>, and high <jats:italic>f</jats:italic> <jats:sub>T</jats:sub> × <jats:italic>L</jats:italic> <jats:sub>g</jats:sub> of 13.44 GHz⋅μm. A transmission electron microscope (TEM) imaging illustrates an oxide layer with a thickness of 1.8 nm exists at the AlGaN surface. X-ray photoelectron spectroscopy (XPS) measurement shows that the content of the Al–O and Ga–O bonds elevated after IST, indicating that the Al–N and Ga–N bonds on the AlGaN surface were broken and meanwhile the Al–O and Ga–O bonds formed. The oxide formed by a chemical reaction between radicals and the surface of the AlGaN barrier layer is responsible for improved device characteristics.</jats:p>

<jats:p>The quantum Hall effect (QHE), which is usually observed in two-dimensional systems, was predicted theoretically and observed experimentally in three-dimensional (3D) topological semimetal. However, there are some inconsistencies between the theory and the experiments showing the theory is imperfect. Here, we generalize the theory of the 3D QHE of Fermi arcs in Weyl semimetal. Through calculating the sheet Hall conductivity of a Weyl semimetal slab, we show that the 3D QHE of Fermi arcs can occur in a large energy range and the thickness dependences of the QHE in different Fermi energies are distinct. When the Fermi energy is near the Weyl nodes, the Fermi arcs give rise to the QHE which is independent of the thickness of the slab. When the Fermi energy is not near the Weyl nodes, the two Fermi arcs form a complete Fermi loop with the assistance of bulk states giving rise to the QHE which is dependent on the sample thickness. We also demonstrate how the band anisotropic terms influence the QHE of Fermi arcs. Our theory complements the imperfections of the present theory of 3D QHE of Fermi arcs.</jats:p>

<jats:p>Pr<jats:sub>0.5</jats:sub>Sr<jats:sub>0.5</jats:sub>FeO<jats:sub>3</jats:sub> (PSFO) and La<jats:sub>0.25</jats:sub>Pr<jats:sub>0.25</jats:sub>Sr<jats:sub>0.5</jats:sub>FeO<jats:sub>3</jats:sub> (LPSFO) nanofibers are prepared by electrospinning followed by calcination, and their morphologies, microstructures, electronic transports, and magnetic properties are studied systematically. The temperature-dependent resistance curves of PSFO and LPSFO nanofibers are measured in a temperature range from 300 K to 10 K. With the temperature lowering, the resistance increases gradually and then decreases sharply due to the occurrence of ferromagnetic metal phase. The metal–insulator transition temperatures are about 110 K and 180 K for PSFO and LPSFO nanofibers, respectively. The electronic conduction behavior above the transition temperature can be described by one-dimensional Mott’s variable-range hopping (VRH) model. The hysteresis loops and the field-cooled (FC) and zero-field-cooled (ZFC) curves show that both PSFO nanofiber and LPSFO nanofiber exhibit ferromagnetism. Although the doping of La reduces the overall magnetization intensity of the material, it increases the ferromagnetic ratio of the system, which may improve the performance of LPSFO in solid oxide fuel cell.</jats:p>

<jats:p>Introduction of spin–orbit coupling (SOC) in a Josephson junction (JJ) gives rise to unusual Josephson effects. We investigate JJs based on a newly discovered heterodimensional superlattice V<jats:sub>5</jats:sub>S<jats:sub>8</jats:sub> with a special form of SOC. The unique homointerface of our JJs enables elimination of extrinsic effects due to interfaces and disorder. We observe asymmetric Fraunhofer patterns with respect to both the perpendicular magnetic field and the current. The asymmetry is influenced by an in-plane magnetic field. Analysis of the pattern points to a nontrivial spatial distribution of the Josephson current that is intrinsic to the SOC in V<jats:sub>5</jats:sub>S<jats:sub>8</jats:sub>.</jats:p>

<jats:p>The two-dimensional (2D) kagome superconductor CsV<jats:sub>3</jats:sub>Sb<jats:sub>5</jats:sub> has attracted much recent attention due to the coexistence of superconductivity, charge orders, topology and kagome physics, which manifest themselves as distinct electronic structures in both bulk and surface states of the material. An interesting next step is to manipulate the electronic states in this system. Here, we report angle-resolved photoemission spectroscopy (ARPES) evidence for a surface-induced orbital-selective band reconstruction in CsV<jats:sub>3</jats:sub>Sb<jats:sub>5</jats:sub>. A significant energy shift of the electron-like band around <jats:italic>Γ</jats:italic> and a moderate energy shift of the hole-like band around <jats:italic>M</jats:italic> are observed as a function of time. This evolution is reproduced in a much shorter time scale by <jats:italic>in-situ</jats:italic> annealing of the CsV<jats:sub>3</jats:sub>Sb<jats:sub>5</jats:sub> sample. Orbital-resolved density functional theory (DFT) calculations reveal that the momentum-dependent band reconstruction is associated with different orbitals for the bands around <jats:italic>Γ</jats:italic> and <jats:italic>M</jats:italic>, and the time-dependent evolution points to the change of sample surface that is likely caused by the formation of Cs vacancies on the surface. Our results indicate the possibility of orbital-selective control of the band structure via surface modification, which may open a new avenue for manipulating exotic phenomena in this material system, including superconductivity.</jats:p>

<jats:p>As a van der Waals ferromagnet with high Curie temperature, Fe<jats:sub>5–<jats:italic>x</jats:italic> </jats:sub>GeTe<jats:sub>2</jats:sub> has attracted tremendous interests recently. Here, using high-resolution angle-resolved photoemission spectroscopy (ARPES), we systematically investigated the electronic structure of Fe<jats:sub>5–<jats:italic>x</jats:italic> </jats:sub>GeTe<jats:sub>2</jats:sub> crystals and its temperature evolution. Our ARPES measurement reveals two types of band structures from two different terminations with slight <jats:italic>k<jats:sub>z</jats:sub> </jats:italic> evolution. Interestingly, across the ferromagnetic transition, we observed the merging of two split bands above the Curie temperature, suggesting the band splitting due to the exchange interaction within the itinerant Stoner model. Our results provide important insights into the electronic and magnetic properties of Fe<jats:sub>5–<jats:italic>x</jats:italic> </jats:sub>GeTe<jats:sub>2</jats:sub> and the understanding of magnetism in a two-dimensional ferromagnetic system.</jats:p>

<jats:p>We study the critical scaling and dynamical signatures of fractionalized excitations at two different deconfined quantum critical points (DQCPs) in an <jats:italic>S</jats:italic> = 1/2 spin chain using the time evolution of infinite matrix product states. The scaling of the correlation functions and the dispersion of the conserved current correlations explicitly show the emergence of enhanced continuous symmetries at these DQCPs. The dynamical structure factors in several different channels reveal the development of deconfined fractionalized excitations at the DQCPs. Furthermore, we find an effective spin–charge separation at the DQCP between the ferromagnetic (FM) and valence bond solid (VBS) phases, and identify two continua associated with different types of fractionalized excitations at the DQCP between the <jats:italic>X</jats:italic>-direction and <jats:italic>Z</jats:italic>-direction FM phases. Our findings not only provide direct evidence for the DQCP in one dimension but also shed light on exploring the DQCP in higher dimensions.</jats:p>

<jats:p>We report an investigation on the single crystal growth, magnetic and transport properties of EuIn<jats:sub>2</jats:sub>(As<jats:sub>1−<jats:italic>x</jats:italic> </jats:sub>P<jats:sub> <jats:italic>x</jats:italic> </jats:sub>)<jats:sub>2</jats:sub> (0 ≤ <jats:italic>x</jats:italic> ≤ 1). The physical properties of axion insulator candidate EuIn<jats:sub>2</jats:sub>As<jats:sub>2</jats:sub> can be effectively tuned by P-doping. With increasing <jats:italic>x</jats:italic>, the <jats:italic>c</jats:italic>-axis lattice parameter decreases linearly, the magnetic transition temperature gradually increases and ferromagnetic interactions are enhanced. This is similar to the previously reported high pressure effect on EuIn<jats:sub>2</jats:sub>As<jats:sub>2</jats:sub>. For <jats:italic>x</jats:italic> = 0.40, a spin glass state at <jats:italic>T</jats:italic> <jats:sub>g</jats:sub> = 10 K emerges together with the observations of a butter-fly shaped magnetic hysteresis and slow magnetic behavior. Besides, magnetic transition has great influence on the charge carriers in this system and negative colossal magnetoresistance is observed for all P-doped samples. Our findings suggest that EuIn<jats:sub>2</jats:sub>(As<jats:sub>1−<jats:italic>x</jats:italic> </jats:sub>P<jats:sub> <jats:italic>x</jats:italic> </jats:sub>)<jats:sub>2</jats:sub> is a promising material playground for exploring novel topological states.</jats:p>

<jats:p>The 52% energy of the solar radiation is contributed by near-infrared radiation (NIR, 780–2500 nm). Therefore, the material design for the energy-saving smart window, which can effectively shield NIR and has acceptable visible transmittance, is vital to save the energy consumed on the temperature control system. It is important to find a non-toxic stable material with excellent NIR-shielding ability and acceptable visible transmittance. The systematic first-principles study on Li<jats:sub> <jats:italic>x</jats:italic> </jats:sub>Sn<jats:sub> <jats:italic>y</jats:italic> </jats:sub>WO<jats:sub>3</jats:sub> (<jats:italic>x</jats:italic> = 0, 0.33, 0.66, and <jats:italic>y</jats:italic> = 0, 0.33) exhibits that the chemical stability is a positive correlation with the doping concentration. After doping, the Fermi-energy upshifts into the conduction band, and the material shows metal-like characteristics. Therefore, these structures Li<jats:sub> <jats:italic>x</jats:italic> </jats:sub>Sn<jats:sub> <jats:italic>y</jats:italic> </jats:sub>WO<jats:sub>3</jats:sub> (except the structure with <jats:italic>x</jats:italic> = 0.33 and <jats:italic>y</jats:italic> = 0) show pronounced improvement of NIR shielding ability. Our results indicate that when <jats:italic>x</jats:italic> = 0 and <jats:italic>y</jats:italic> = 0.33, the material exhibits the strongest NIR-shielding ability, satisfying chemical stability, wide NIR-shielding range (780–2500 nm), and acceptable visible transmittance. This work provides a good choice for experimental study on NIR shielding material for the energy-saving window.</jats:p>

<jats:p>V-based kagome materials <jats:italic>A</jats:italic>V<jats:sub>3</jats:sub>Sb<jats:sub>5</jats:sub> (<jats:italic>A</jats:italic> = K, Rb, Cs) have attracted much attention due to their novel properties such as unconventional superconductivity, giant anomalous Hall effect, charge density wave (CDW) and pair density wave. Except for the 2<jats:italic>a</jats:italic> <jats:sub>0</jats:sub> × 2<jats:italic>a</jats:italic> <jats:sub>0</jats:sub> CDW (charge density wave with in-plane 2 × 2 superlattice modulation) in <jats:italic>A</jats:italic>V<jats:sub>3</jats:sub>Sb<jats:sub>5</jats:sub>, an additional 1 × 4 (4<jats:italic>a</jats:italic> <jats:sub>0</jats:sub>) unidirectional stripe order has been observed at the Sb surface of RbV<jats:sub>3</jats:sub>Sb<jats:sub>5</jats:sub> and CsV<jats:sub>3</jats:sub>Sb<jats:sub>5</jats:sub>. However, the stability and electronic nature of the 4<jats:italic>a</jats:italic> <jats:sub>0</jats:sub> stripe order remain controversial and unclear. Here, by using low-temperature scanning tunneling microscopy/spectroscopy (STM/S), we systematically study the 4<jats:italic>a</jats:italic> <jats:sub>0</jats:sub> stripe order on the Sb-terminated surface of CsV<jats:sub>3</jats:sub>Sb<jats:sub>5</jats:sub>. We find that the 4<jats:italic>a</jats:italic> <jats:sub>0</jats:sub> stripe order is visible in a large energy range. The STM images with positive and negative bias show contrast inversion, which is the hallmark for the Peierls-type CDW. In addition, below the critical temperature about 60 K, the 4<jats:italic>a</jats:italic> <jats:sub>0</jats:sub> stripe order keeps unaffected against the topmost Cs atoms, point defects, step edges and magnetic field up to 8 T. Our results provide experimental evidences on the existence of unidirectional CDW in CsV<jats:sub>3</jats:sub>Sb<jats:sub>5</jats:sub>.</jats:p>