Modern Physics Letters B

We review a natural universal theoretical framework of superfluidity and its analogues, superconductivity and supersolidity. This framework has the potential to describe all physical properties of superfluids to a high level of satisfaction. A unified description of both the "intrinsic" and "extrinsic" critical velocity of liquid ⁴He is suggested. A recent clarification of the so-call pseudogap phase of a superconductor based on this framework is introduced. This paper reflects the current author's views of superfluidity, rather than being an attempt to review on a vast literature on this subject.

High dielectric hafnium oxide films were grown by magnetron sputtering and post heat treatment in nitrogen atmosphere at 500°C for 30 min using vacuum annealing furnace. The film keeps amorphous at 500°C and has better interface quality as revealed by X-ray diffraction and transmission electron microscopy. The influence of TiN and Pt electrodes on the electrical property of the film was compared. For the annealed films, TiN electrode was presented as the optimal one. For the conduction mechanism of Pt/HfO₂/p-Si MOS capacitors under gate electron injection, the dominant conduction mechanism at low electric field is Schottky emission. At high electric field, the conversion of current transport mechanism from Schottky emission to trap-assisted tunneling for the annealed HfO₂ film occurs at 0.64 MV/cm.

We propose a method to use gapped graphene as barriers to confine electrons in gapless graphene and form a good quantum dot, which can be realized on an oxygen-terminated SiO₂ substrate partly hydrogen-passivated. In particular, we use deposited ferromagnetic insulators as contacts which give rise to spin-dependent energy spectrum and transport properties. Furthermore, we upgrade this method to form two-dimensional quantum dot arrays, whose coupling strength between neighboring dots can be uniquely anisotropic. Compared to complexity of other approaches to form quantum dot in graphene, the setup suggested here is a promising candidate for practical applications.

In this paper, we investigate the temperature dependence of the transverse conductivity in Y_1-zPr_zBa₂Cu₃O_7-δ single crystals with different praseodymium concentrations. It is determined that the increase of the praseodymium concentration in Y_1-zPr_zBa₂Cu₃O_7-δ leads to the enhancement of localization effects. This in turn results to the transition from the pseudo-gap regime to the variable-range-hopping regime.

In the shallow-water studies, the Whitham–Broer–Kaup (WBK) system can be used to describe the propagation of the long waves. In this paper, based on the Lax pair of the WBK system, we derive the gauge transformation from the WBK system to the Ablowitz–Kaup–Newell–Segur (AKNS) system with the help of symbolic computation. Applying the Darboux transformation of the AKNS system, we obtain some soliton solutions of the WBK system. Those results might be useful in the investigations on the propagation of solitons in such situation as shallow water.

Quantum correlations (including entanglement and quantum discord) of two qubits symmetrically coupled to the surrounding XY spin chain in the presence of a transverse magnetic field are studied. We investigate the dynamic evolution of the quantum correlations of the two qubits when the surrounding spin chain is in the thermal equilibrium state. Numerical results show that the thermal effects can accelerate the decay process of the quantum correlations if the initial state of the composite system is not in the decoherence free space. When the temperature is high enough, the quantum phase transition driven by the external magnetic field completely disappear.

Strain effects on hydrogen sulphide (H₂S) adsorption on Ag-decorated Stone–Wales (SW) defect in graphene were investigated by density functional theory calculations. The results indicate that an Ag adatom is easily pinned chemically on the top of the most stretched C–C bond at the SW defect in graphene without mechanical strains. A modest uniform tensile strain (8%) applied in defective graphene greatly increases the binding energy of Ag by 44%, indicating the strain enhanced stabilization of Ag on SW defect. Using the resulting Ag-decorated defective graphene (Ag–SW–g) composite as a model for H₂S molecule detection, we found that the tensile strain has little effects on the interaction between the molecule and the composite, and the adsorption energies of H₂S around 1.6 eV which is six times larger than that on pristine graphene are produced. The enhanced H₂S adsorption on Ag–SW–g is attributed to charge transfer from the molecule to the graphene through the bridge-like Ag adatom. In addition, the electronic property of the Ag–SW–g under different strains changes from a metallic state to a semiconductor state upon H₂S adsorption, which should lead to an observable change in its conductivity. These findings pave the way for future development of graphene-based gas sensor.

The magnetic properties and magnetocaloric effect of the polycrystalline Gd₃Ni₈Al intermetallic compound are studied in this paper. Powder X-ray diffraction shows that the alloy is CeNi₃-type single-phase structure. The magnetic measurements indicate that the compound is ferromagnetic and undergoes a second-order phase transition at 62 K. The maximum of magnetic entropy change reaches 11 J/kg K for the field change from 0 to 50 kOe and the refrigerant capacity of the titled compound is found to be 4.8×10² J/kg.