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<jats:p>We present a high-pressure study of van der Waals ferromagnetic metal Fe<jats:sub>3</jats:sub>GeTe<jats:sub>2</jats:sub> through electrical transport and Raman scattering measurements in diamond anvil cells at pressures up to 22.4GPa. Upon compression, the ferromagnetic transition temperature <jats:italic>T</jats:italic> <jats:sub>c</jats:sub> manifested by a kink in resistance curve decreases monotonically and becomes undiscernable around <jats:italic>P</jats:italic> <jats:sub>c</jats:sub> = 10GPa, indicative of suppression of the itinerant ferromagnetism. Meanwhile, by fitting the low temperature resistance to the Fermi liquid behavior of <jats:italic>R</jats:italic> = <jats:italic>R</jats:italic> <jats:sub>0</jats:sub> + <jats:italic>AT</jats:italic> <jats:sup>2</jats:sup>, we found that <jats:italic>R</jats:italic> <jats:sub>0</jats:sub> shows a cusp-like anomaly and the coefficient <jats:italic>A</jats:italic> diverges around <jats:italic>P</jats:italic> <jats:sub>c</jats:sub>. These transport anomalies imply a tricritical point as commonly observed in itinerant ferromagnets under pressure. Unexpectedly, the Raman-active <jats:italic>E</jats:italic> <jats:sub>2<jats:italic>g</jats:italic> </jats:sub> and <jats:italic>A</jats:italic> <jats:sub>1<jats:italic>g</jats:italic> </jats:sub> modes soften remarkably after an initial weak hardening and the peak widths of both modes broaden evidently on approaching <jats:italic>P</jats:italic> <jats:sub>c</jats:sub>, followed by complete disappearance of both modes above this critical pressure. A possible underlying mechanism for such anomalous lattice softening near <jats:italic>P</jats:italic> <jats:sub>c</jats:sub> is discussed.</jats:p>

<jats:p>Layered black phosphorus (BP) has recently emerged as a promising semiconductor because of its tunable band gap, high carrier mobility and strongly in-plane anisotropic properties. One-dimensional (1D) BP materials are attractive for applications in electronic and thermal devices, owing to their tailored charge and phonon transports along certain orientations. However, the fabrication of 1D BP materials still remains elusive thus far. We herein report the successful synthesis and characterization of nanotube-like BP for the first time by a selective composite with hexagonal boron nitride (h-BN) nanotubes under high pressure and high temperature conditions. The produced 1D BP/h-BN composites possess flexible diameter, length and thickness by adjusting the experimental synthesis parameters. Interestingly, it is important to notice that the stability of our BP sample has been significantly improved under the formation of heterostructures, which can actively promote their commercial applications. Our experimental work, together with first-principles calculations, presents a new scalable strategy of designing 1D tube-like BP/h-BN heterostructures that are promising candidates for flexible and high efficiency electronic platform.</jats:p>

<jats:p>A theoretical study on the structural dynamics of the temporal behavior of Bragg diffraction is presented and compared with experimental results obtained via ultrafast electron crystallography. In order to describe the time-dependent lattices and calculate the Bragg diffraction intensity, we introduce the basic vector offset matrix, which can be used to quantify the shortening, lengthening and rotation of the three lattice vectors (i.e., lattice deformation). Extensive simulations are performed to evaluate the four-dimensional electron crystallography model. The results elucidate the connection between structural deformations and changes in diffraction peaks, and sheds light on the quantitative analysis and comprehensive understanding of the structural dynamics.</jats:p>

<jats:p>We study the formation of quantum droplets in the mixture of a single-component Bose–Einstein condensate (BEC), and a two-species Fermi superfluid across a wide Feshbach resonance. With repulsive boson-boson and attractive boson-fermion interactions, we show that quantum droplets can be stabilized by attractive fermion-fermion interactions on the Bardeen–Cooper–Schrieffer (BCS) side of the resonance, and can also exist in the deep BEC regime under weak boson-fermion interactions. We map out the phase diagram for stable droplets with respect to the boson-boson and boson-fermion interactions, and discuss the role of different types of quantum fluctuations in the relevant regions of the BCS-BEC crossover. Our work reveals the impact of fermion pairing on the formation of quantum droplets in Bose–Fermi mixtures, and provides a useful guide for future experiments.</jats:p>

<jats:p>Due to the lack of surface dangling bonds in graphene, the direct growth of high-<jats:italic>κ</jats:italic> films via atomic layer deposition (ALD) technique often produces the dielectrics with a poor quality, which hinders its integration in modern semiconductor industry. Previous pretreatment approaches, such as chemical functionalization with ozone and plasma treatments, would inevitably degrade the quality of the underlying graphene. Here, we tackled this problem by utilizing an effective and convenient physical method. In detail, the graphene surface was pretreated with the deposition of thermally evaporated ultrathin Al metal layer prior to the Al<jats:sub>2</jats:sub>O<jats:sub>3</jats:sub> growth by ALD. Then the device was placed in a drying oven for 30 min to be naturally oxidized as a seed layer. With the assistance of an Al oxide seed layer, pinhole-free Al<jats:sub>2</jats:sub>O<jats:sub>3</jats:sub> dielectrics growth on graphene was achieved. No detective defects or disorders were introduced into graphene by Raman characterization. Moreover, our fabricated graphene top-gated field effect transistor exhibited high mobility (∼6200 cm<jats:sup>2</jats:sup>V<jats:sup>−1</jats:sup>s<jats:sup>−1</jats:sup>) and high transconductance (∼117 <jats:italic>μ</jats:italic>S). Thin dielectrics demonstrated a relative permittivity of 6.5 over a large area and a leakage current less than 1.6 pA/<jats:italic>μ</jats:italic>m<jats:sup>2</jats:sup>. These results indicate that Al oxide functionalization is a promising pathway to achieve scaled gate dielectrics on graphene with high performance.</jats:p>

<jats:p>Hybrid structures of two distinct materials provide an excellent opportunity to optimize functionalities. We report the realization of wide quantum Hall plateaus in graphene field-effect devices on the LaAlO<jats:sub>3</jats:sub>/SrTiO<jats:sub>3</jats:sub> heterostructures. Well-defined quantized Hall resistance plateaus at filling factors <jats:italic>v</jats:italic> = ± 2 can be obtained over wide ranges of the magnetic field and gate voltage, e.g., extending from 2 T to a maximum available magnetic field of 9 T. By using a simple band diagram model, it is revealed that these wide plateaus arise from the ultra-large capacitance of the ultra-thin LAO layer acting as the dielectric layer. This is distinctly different from the case of epitaxial graphene on SiC substrates, where the realization of giant Hall plateaus relies on the charge transfer between the graphene layer and interface states in SiC. Our results offer an alternative route towards optimizing the quantum Hall performance of graphene, which may find its applications in the further development of quantum resistance metrology.</jats:p>

<jats:p>The energy band alignment at the atomic layer deposited Al<jats:sub>2</jats:sub>O<jats:sub>3</jats:sub>/<jats:italic>β</jats:italic>-Ga<jats:sub>2</jats:sub>O<jats:sub>3</jats:sub> interface with CHF<jats:sub>3</jats:sub> treatment was characterized by x-ray photoelectron spectroscopy and secondary ion mass spectrometry (SIMS). With additional CHF<jats:sub>3</jats:sub> plasma treatment, the conduction band offset increases from 1.95±0.1 eV to 2.32±0.1 eV; and the valence band offset decreases from 0.21±0.1 eV to −0.16±0.1 eV. As a result, the energy band alignment changes from type I to type II. This energy band alignment transition could be attributed to the downshift of the core-level of Ga 3<jats:italic>d</jats:italic>, resulting from the Ga–F bond formation in the F-rich interfacial layer, which is confirmed by the SIMS results.</jats:p>

<jats:p>An ultra-thin Co<jats:sub>2</jats:sub>MnSi(0.5 nm)/MnGa(1.5 nm) bilayer capped with Pt (5 nm) has been successfully grown by molecular-beam epitaxy. It is a potential candidate of synthetic antiferromagnets due to antiferromagnetic coupling between Co<jats:sub>2</jats:sub>MnSi and MnGa, which is a promising skyrmion-racetrack-memory medium without skyrmion Hall effect after capping with a Pt layer. Unusual humps in transverse Hall resistance loops are clearly observed in the temperature range from 260 to 400 K. This anomaly is generally attributed to topological Hall effect, but other than that, we prove that non-uniform rotation of magnetic moments in the bilayer with magnetic field sweeping is also a possible mechanism contributed to the unusual hump.</jats:p>

<jats:p>We investigate the interface between a three-dimensional Dirac semimetal Cd<jats:sub>3</jats:sub>As<jats:sub>2</jats:sub> and a normal metal via soft-point contact spectroscopy measurement. The superconducting gap features were detected below 3.8 K and 7.1 K in the case of Cd<jats:sub>3</jats:sub>As<jats:sub>2</jats:sub> single crystals sputter-coated with the Pt and Au films, respectively, in the differential conductance <jats:italic>dI</jats:italic>/<jats:italic>dV</jats:italic>–<jats:italic>V</jats:italic> plots of the point contacts. As the applied magnetic field increased, the drop in the zero-bias contact resistance shifted toward lower temperatures. The topologically non-trivial band structure of Cd<jats:sub>3</jats:sub>As<jats:sub>2</jats:sub> is considered to play a crucial role in inducing the superconductivity. Apart from realizing superconductivity in topological materials, our creative approach can be used to investigate possible topological superconductivity and exhibits a high application potential in electronic devices.</jats:p>

<jats:p>The ternary topological insulators Bi<jats:sub>2</jats:sub>Se<jats:sub>3 − <jats:italic>x</jats:italic> </jats:sub>Te<jats:sub> <jats:italic>x</jats:italic> </jats:sub> have attracted a great deal of attention due to their exotic physical and chemical properties. While most of the studies focus on the properties of these ternary TIs, limited research was performed to investigate the dynamic atomic stack of its crystal structure. We prepared high-quality Bi<jats:sub>2</jats:sub>Se<jats:sub>3 − <jats:italic>x</jats:italic> </jats:sub>Te<jats:sub> <jats:italic>x</jats:italic> </jats:sub> thin films on GaAs(111)B substrates using molecular beam epitaxy, characterized with Raman spectroscopy, x-ray diffraction and photoelectron spectroscopy. It is found that when Se is replaced by Te, the preferred substituting sites are the middle layer at 0 &lt; <jats:italic>x</jats:italic> &lt; 1, and this is also valid for Se substituting Te at 2 &lt; <jats:italic>x</jats:italic> &lt; 3. In the middle region, the substituting atoms prefer to go to the first and the fifth layer.</jats:p>