Research interest in ZnO nanostructures derives from their excellent luminescent properties and availability of low cost fabricating and processing, which hold promise for the development of electronic and optoelectronic nanodevices. In this review, we focus on the progress in synthesis, properties and nanodevices of ZnO nanorod (NR) arrays and nanotetrapods (NTPs). Recent work done by the authors are also presented. After a brief introduction to the controlled fabrication methods for the highly-ordered ZnO NR arrays and NTPs, we present some aspects of the fundamental properties, especially optical performance, of ZnO NRs/NTPs. Then, we provide an overview of the applications to functional nanodevices based on individual NR and NTP of ZnO. It is demonstrated that different morphologies of ZnO nanostructures have salient effects on their properties and applications. Although much progress has been achieved in the fundamental and applied investigations of ZnO NRs/NTPs over the past decade, many obstacles still remain, hampering further development in this field. Finally, some longstanding problems that warrant further investigation are addressed.

The atomistic mechanism for direct conversion of graphite to diamond is a long-standing problem in condensed matter physics. The newly identified cold-compressed graphite phases of M, W and O carbon provide a crucial link to understand the graphite-todiamond phase transformation. We demonstrate by ab initio calculations that pressure has a dual role in lowering the conversion barrier and enhancing the production stability during the first-stage cold-compressed phase conversion of graphite toward the intermediate metastable M, W and O carbon phases. However, it has little effect on the relative enthalpy and high conversion barrier during the second-stage conversion process toward the diamond polytypes, showing a temperature dominated conversion process. These results may give explanation regarding the necessity of high pressure and high temperature during the graphite-todiamond reaction.

Higgs type excitations are the excitations which give mass to particles. The Higgs type excitations has a critical role both in particle physics and condensed matter physics. In particle physics, the suspected Higgs boson has been found by the Large Hadron Collider (LHC) in 2012. In condensed matter physics, the Higgs type excitations relate to order phase of the system. In this review, we present an overview of recent studies on the Higgs type excitations both in non-interacting and interacting cold atom systems. First, in non-interacting cold atom system, by synthesizing artificial non-Abelian gauge potential, we demonstrate that when a non-Abelian gauge potential is reduced to Abelian potential, the Abelian part constructs spin-orbit coupling, and the non-Abelian part emerges Higgs excitations. Secondly, the Higgs excitations which are the reputed Higgs amplitude mode in interacting cold atom system are discussed. We review the theoretical model and the experimental detection of Higgs amplitude mode in two dimensional superfluid. The observation of both Higgs type excitations in real experiments are also discussed.

The physics that associated with the performance of lithium secondary batteries (LSB) are reviewed. The key physical problems in LSB include the electronic conduction mechanism, kinetics and thermodynamics of lithium ion migration, electrode/electrolyte surface/interface, structural (phase) and thermodynamics stability of the electrode materials, physics of intercalation and deintercalation. The relationship between the physical/chemical nature of the LSB materials and the batteries performance is summarized and discussed. A general thread of computational materials design for LSB materials is emphasized concerning all the discussed physics problems. In order to fasten the progress of the new materials discovery and design for the next generation LSB, the Materials Genome Initiative (MGI) for LSB materials is a promising strategy and the related requirements are highlighted.

A review on the formation and unique physical and mechanical properties of metallic glassy fibers (MGFs) with the diameter ranging from micro to nano scales fabricated by a supercooled liquid extraction method (SLEM) is given. The SLEM method, through driving metallic glass rods in their supercooled liquid region via superplasticity, can fabricate MGFs with precisely designed and controlled size and properties, high structural uniformity and surface smoothness and extreme flexibility. The SLEM method is efficient and the MGFs can be continuously prepared by this method. A parameter f based on the thermal and rheological properties of MG-forming alloys is proposed to control the preparation and size of the fibers. We show that the novel MGFs with superior properties may attract intensive scientific interests and propel more engineering and functional applications.

La(Fe, Si)₁₃-based compounds have been considered as promising candidates for magnetic refrigerants particularly near room temperature. Herein we review recent progress particularly in the study of the effects of interstitial H and/or C atoms on the magnetic and magnetocaloric properties of La(Fe, Si)₁₃ compounds. By introducing H and/or C atoms, the Curie temperature T_C increases notably with the increase of lattice expansion which makes the Fe 3d band narrow and reduces the overlap of the Fe 3d wave functions. The first-order itinerant-electron metamagnetic transition is conserved and the MCE still remains high after hydrogen absorption. In contrast, the characteristic of magnetic transition varies from first-order to second-order with the increase of C concentration, which leads to remarkable reduction of thermal and magnetic hysteresis. In addition, the introduction of interstitial C atoms promotes the formation of NaZn₁₃-type (1:13) phase in La(Fe, Si)₁₃ compounds, and thus reducing the annealing time significantly from 40 days for LaFe_11.7Si_1.3 to a week for LaFe_11.7Si_1.3C_0.2. The pre-occupied interstitial C atoms may depress the rate of hydrogen absorption and release, which is favorable to the accurate control of hydrogen content. It is found that the reduction of particle size would greatly depress the hysteresis loss and improve the hydrogenation process. By the incorporation of both H and C atoms, large MCE without hysteresis loss can be obtained in La(Fe, Si)₁₃ compounds around room temperature, for instance, La_0.7Pr_0.3Fe_11.5Si_1.5C_0.2H_1.2 exhibits a large |ΔS_M| of 22.1 J/(kg·K) at T_C=321 K without hysteresis loss for a field change of 0?5 T.

Interface and surface physics is an important sub-discipline within condensed matter physics in recent decades. Novel concepts like oxide-electronic device are prompted, and their performance and lifetime are highly dependent on the flatness and abruptness of the layer surfaces and interfaces. Reflection high-energy electron diffraction (RHEED), which is extremely sensitive to surface morphology, has proven to be a versatile technique for the growth study of oxide thin films. A differential pumping unit enables an implementation of RHEED to pulsed laser deposition (PLD) systems, ensuring an in situ monitoring of the film growth process in a conventional PLD working oxygen pressure up to 30 Pa. By optimizing the deposition conditions and analyzing the RHEED intensity oscillations, layer-by-layer growth mode can be attained. Thus atomic control of the film surface and unit-cell control of the film thickness become reality. This may lead to an advanced miniaturization in the oxide electronics, and more importantly the discovery of a range of emergent physical properties at the interfaces. Herein we will briefly introduce the principle of high-pressure RHEED and summarize our main results relevant to the effort toward this objective, including the growth and characterization of twinned La_2/3Ca_1/3MnO₃ thin films and ReTiO_3+δ/2 (Re=La, Nd;δ=0~1) A_nB_nO_3n+2 structures, on YSZ-buffered ‘Silicon on Insulator’and LaAlO₃ substrates, respectively, as well as the study of the initial structure and growth dynamics of YBa₂Cu₃O_7-δ thin films on SrTiO₃ substrate. Presently we have realized in situ monitoring and growth mode control during oxide thin film deposition process.

Noble metal nanostructures possess novel optical properties because of their collective electronic oscillations, known as surface plasmons (SPs). The resonance of SPs strongly depends on the material, surrounding environment, as well as the geometry of the nanostructures. Complex metal nanostructures have attracted research interest because of the degree of freedom in tailoring the plasmonic properties for more advanced applications that are unattainable by simple ones. In this review, we discuss the plasmonic properties of several typical types of complex metal nanostructures, that is, electromagnetically coupled nanoparticles (NPs), NPs/metal films, NPs/nanowires (NWs), NWs/NWs, and metal nanostructures supported or coated by dielectrics. The electromagnetic field enhancement and surface-enhanced Raman scattering applications are mainly discussed in the NPs systems where localized SPs have a key role. Propagating surface plasmon polaritons and relevant applications in plasmonic routers and logic gates using NWs network are also reviewed. The effect of dielectric substrates and surroundings of metal nanostructures to the plasmonic properties is also discussed.

In this article we briefly review new quantum functional compounds primarily based on our recent works. We will highlight the effects of pressures on both materials synthesis and quantum tuning. The contents include (Ⅰ) "111"-type iron based superconducting system, (Ⅱ) pressure induced superconductivity in topological insulators and (Ⅲ) the new diluted magnetic semiconductors with decoupled spin charge doping.

Since their advent in the 1980s, optical tweezers have attracted more and more attention due to their unique non-contact and non-invasion characteristics and their wide applications in physics, biology, chemistry, medical science and nanoscience. In this paper, we introduce the basic principle, the history and typical applications of optical tweezers and review our recent experimental works on the development and application of optical tweezers technique. We will discuss in detail several technological issues, including high precision displacement and force measurement in single-trap and dual-trap optical tweezers, multi-trap optical tweezers with each trap independently and freely controlled by means of space light modulator, and incorporation of cylindrical vector optical beams to build diversified optical tweezers beyond the conventional Gaussian-beam optical tweezers. We will address the application of these optical tweezers techniques to study biophysical problems such as mechanical deformation of cell membrane and binding energy between plant microtubule and microtubule associated proteins. Finally we present application of the optical tweezers technique for trapping, transporting, and patterning of metallic nanoparticles, which can be harnessed to manipulate surface plasmon resonance properties of these nanoparticles.

Resistive switching random access memories (RRAM) have been considered to be promising for future information technology with applications for non-volatile memory, logic circuits and neuromorphic computing. Key performances of those resistive devices are approaching the realistic levels for production. In this paper, we review the progress of valence change type memories, including relevant work reported by our group. Both electrode engineering and in-situ transmission electron microscopy (TEM) high-resolution observation have been implemented to reveal the influence of migration of oxygen anions/vacancies on the resistive switching effect. The understanding of resistive memory mechanism is significantly important for device applications.

The symmetry of the surfaces of SrTiO₃ and slightly Nb-doped SrTiO₃ crystals was investigated by the optical reflected second harmonic generation technique. The good agreement between experimental and theoretical results of the second harmonic intensity dependence on the azimuth angle indicates that the SrTiO₃ (001) surface is with 4mm symmetry and the Nb-doped SrTiO₃ (111) surface with 3m symmetry. The measurements of the polarization dependent second harmonic intensity confirm that conclusion. The enhancement of the surface polarization in the structure of SrTiO₃ capped La0_.9Sr_0.1MnO₃ films compared with that in the La_0.9Sr_0.1MnO₃ films has been obtained.

Herein we develop an Al/AlO_x/Al trilayer process, feasible to fabricate complex circuits with wiring crossovers, for the preparation of Al junctions and phase qubits. The AlO_x layer is obtained by in situ thermal oxidation, which provides high-quality junction tunnel barriers. The Al junctions show a considerably low leakage current and the Josephson critical current density can be conveniently controlled in the range of a few to above 100 A/cm², which is favorable in the phase qubit application. Macroscopic quantum tunneling, energy spectrum, energy relaxation time, Rabi oscillation, and Ramsey interference of the Al phase qubits are measured, demonstrating clearly quantum coherent dynamics with a timescale of 10 ns. Further improvements of the coherent dynamic properties of the device are discussed.

Interactions of two counter-streaming plasmas driven by high power laser pulses are studied on Shenguang Ⅱ laser facility. Filamentary structures were observed in the interaction region after the electrostatic shockwave decay. Theoretical analysis and observations indicate that the filaments are because of collisionless mechanisms, which are caused by the electromagnetic instability, such as the beam-Weibel instability. Collision experiments were also carried out for comparison and no filaments were generated.

Using novel ideas for the fabrication of epitaxial graphene (EG) on SiC, two forms of graphene termed as vertical aligned graphene sheets (VAGS) and graphene covered SiC powder (GCSP) were derived, respectively, from SiC slices and SiC powder, aimed for applications in energy storage and photocatalysis. Herein, the fabrication procedures, morphology characteristics, some intrinsic physical properties and performances for applications in field effect transistor (FET) and cold cathode field emission source are revealed and analyzed based on the graphene materials. The EG on a 2-inch SiC (0001) showed an average sheet resistance about 720 Ω/□ with a non-uniformity 7.2%. The FETs fabricated on the EG possessed a cutoff frequency 80 GHz. Based on the VAGS derived from a completely carbonized SiC slice, a magnetic phase diagram of graphene with irregular zigzag edges is also reported.

Ultrafast quasiparticle dynamics of single crystalline LaOFeAs were investigated by pump-probe measurement. The compound experiences structural and spin-density-wave (SDW) phase transitions at 150 K (T_S1) and 130 K (T_S2), respectively. The relaxation time of quasiparticles was somewhat temperature independent at high temperature but exhibited a sharp upturn at T_S1 and reached the maximum at approximately T_S2. The remarkable slowing down of quasiparticle relaxation time is caused by the formation of energy gap. By employing the Rothwarf-Taylor model analysis, we found that there should be already energy gaps opening just below the structural transition. The magnitude of SDW gap was identified to be 72 meV.

Herein we investigated the electronic properties of layered transition-metal oxides Na₂Ti₂Sb₂O by ²³Na nuclear magnetic resonance (NMR) measurement. The resistivity, susceptibility and specific heat measurements show a phase transition at approximately 114 K (T_A). No splitting or broadening in the central line of ²³Na NMR spectra is observed below and above the transition temperature indicating no internal field being detected. The spin-lattice relaxation rate divided by T (1/T₁T) shows a sharp drop at about 110 K which suggests a gap opening behavior. Below the phase transition temperature zone, 1/T₁T shows Fermi liquid behavior but with much smaller value indicating the loss of large part of electronic density of states (DOS) because of the gap. No signature of the enhancement of spin fluctuations or magnetic order is found with the decreasing temperature. These results suggest a commensurate charge-density-wave (CDW) phase transition occurring.

SrTiO₃ films with different cation concentration were deposited on Si(001) substrates by oxide molecular beam epitaxy. An amorphous layer was observed at the interface whose thickness depends on the oxygen pressure and the substrate temperature during growth. Although lowering the oxygen vacancy concentration in SrTiO₃ led to better insulating performance as indicated by the lowered leakage current density of the heterostructure, the dielectric performance was deteriorated because of the thickened interfacial layer that dominated the capacitance of SrTiO₃/Si heterostructure. Instead of adjusting the oxygen vacancy concentration, we propose that controlling the film cation concentration is an effective way to tune the dielectric and insulating properties of SrTiO₃/Si at the same time.

The China Spallation Neutron Source (CSNS) is the first accelerator-based multidiscipline user facility to produce pulsed neu-trons by tungsten target under collision of a pulsed proton beam with a beam power of 100 kW at a repetition rate of 25 Hz. In this paper, we focus on the physical design of CSNS target station and neutron instruments. Under optimized design, the flat tungsten target and the compact target-moderator-reflector coupling enhance effective cold and thermal neutron output from moderators. Three wing-type moderators supply four different characteristics of neutrons to 19 beamlines primarily for neutron scattering applications. Layout of neutron instruments are conceptually planned for total 20 beamlines, the configuration and specification have been determined for three day-one neutron instruments. All designs are optimized for the Phase I of 100 kW with a upgradable capacity to 500 kW.