Electrical resistivity and tunneling anomalies in CeCuAs2

The compound CeCuAs2 is found to exhibit negative temperature (T) coefficient of electrical resistivity (rho) under ambient pressure conditions in the entire T-range of investigation (45 mK to 300 K), even in the presence of high magnetic fields. Preliminary tunneling spectroscopic measurements indicate the existence of a psuedo-gap at least at low temperatures, thereby implying that this compound could be classified as a Kondo semi-conductor, though rho(T) interestingly is not found to be of an activated type.Comment: To appear in the proceedings of SCES200

HUBUNGAN ANTARA PENGETAHUAN DENGAN PERILAKU TOILET TRAINING DALAM ISLAM PADA ORANG TUA TODDLER DI GAMPING SLEMAN YOGYAKARTA

Latar Belakang: Toilet training dalam Islam adalah usaha untuk melatih anak agar mampu mengontrol buang air besar dan kecil secara benar sesuai perspektif Islam. Kegagalan toilet training dalam Islam akan berdampak pada anak secara jasmani dan rohani, secara jasmani anak dalam keadaan na jis dan secara rohani anak dalam beribadah tidak sah. Salah satu faktor yang dapat mempengaruhi kegagalan toilet training dalam Islam adalah perilaku orang tua. Perilaku yang buruk pada orang tua akan berdampak pada anak sejak dini. Tujuan : Diketahuinya h ubungan pengetahuan dengan perilaku toilet training dalam Islam pada orang tua toddler di Gamping Sleman Yogyakarta. Metode : Studi korelasional dengan rancangan pendekatan cross sectional . Penelitian melibatkan 49 orang tua yang mempunyai anak usia toddlers diambil dengan teknik total sampling . Data dikumpulkan dengan kuesioner dan dianalisis dengan Kendall’s tau. Hasil : Hasil uji Kendall’s tau menunjukkan pada nilai signifikan p 0 ,000 dan nilai koefisien korelasi 0,455 yang berarti p<0,01. Kesimplan : (1) sebagian besar responden memiliki pen getahuan yang cukup sebanyak 59,2% (2) S ebagian besar responden memiliki perilaku cukup sebanyak 51,0%. (3) P engetahuan dengan perilaku toilet training dalam Islam memiliki hubungan yang signifikan pada orang tua t oddler di Gamping Sleman Yogyakarta. Saran : Penelitian ini menyarankan para orang tua di Gamping Sleman Yogyakarta agar meningkatkan pengetahuan tentang toilet training dalam perspektif Islam sehingga perilaku toilet training dalam Islam akan semakin baik

Parity breaking and phase transition induced by a magnetic field in high TcT_c superconductors

We suggest that the 2+1 dimensional Gross-Neveu model can give an effective field theory description of low-energy quasiparticles in high temperature superconductors. The magnetic catalysis of dynamical symmetry breaking is examined. The model shows that a magnetic field can induce a phase transition associated with parity breaking. In particular, it is intended to give an explanation of a second phase transition observed in a recent experiment by Krishana et al.Comment: Latex 17 pages, 2 figures, added discussions on parity breaking, final version to appear in Nuc. Phys.

Scanning-tunneling microscopy/spectroscopy and break-junction tunneling spectroscopy of FeSe₁–xTex

The iron-chalcogenide superconductor FeSe₁–xTex (0.5 < x < 1) was investigated by scanning-tunneling microscopy/ spectroscopy (STM/STS) and break-junction techniques. In the STM topography of the samples, randomly distributed Te and Se surface atomic structure patterns correlate well with the bulk composition, demonstrating that nanoscale surface features directly reflect bulk properties. The high-bias STS measurements clarified the gap-like structure at ≈ 100–300 meV, which is consistent with the break-junction data. These highenergy structures were also found in sulfur substituted FeS₀.₁Te₀.₉. Possible origin of such spectral peculiarities is discussed. The superconducting gap 2Δ ≈ 3.4 ± 0.2 meV at temperature T = 4.2 K was found in the break junction of FeSe₁–xTex with the critical temperature Tc ≈ 10 K. The corresponding characteristic gap to Tc ratio 2Δ/kBTc ≈ 4 ± 0.2 indicates moderate superconducting coupling (kB is the Boltzmann constant)

Spin-polarized electron tunneling between charge-density-wave metals

For junctions between metals partially gapped by charge density waves (CDWs), the quasiparticle tunnel currents J(V) and conductances G(V) in external magnetic fields H are calculated as functions of H, the bias voltage V, temperature T, the dielectric gaps ∑, and the gapped portions μ of the Fermi surface (FS). The paramagnetic effect of H is taken into account, whereas orbital effects are neglected. General expressions are obtained for different CDW metal electrodes. Analytical formulas are obtained for T = 0. Explicit numerical calculations are carried out for symmetrical junctions. The results are substantially unlike those for junctions between superconductors. It is shown that due to the interplay between quasiparticles from nested and non-nested FS sections the junction properties involve features appropriate to both symmetrical and asymmetrical setups. In particular, for H = 0 discontinuities at eV = ±2∑ and square-root singularities at eV = ±∑ should coexist. Here e is the elementary charge. For H ≠ 0 the former remain intact, while the latter split. It is suggested to use the splitting as a verification of the CDW nature of the pseudogap in high-Tc superconducting oxides

Paramagnetic effect of the magnetic field on superconductors with charge-density waves

The limiting field Hp for spin-singlet superconductors with charge-density waves (CDWs), which paramagnetically destroys the ordered phase, possessing coexisting superconducting and CDW order parameters, is calculated self-consistently. It is shown that Hp always exceeds the Pauli limits both for pure superconducting and pure CDW phases. Relevant experimental data for inorganic and organic superconductors with high upper critical magnetic fields are analyzed and are shown to be in qualitative agreement with the proposed theory

Analysis of the pseudogap-related structure in tunnel spectra of the superconducting Bi₂Sr₂CaCu₂O₈₊δ revealed by break-junction technique

Tunnel conductance G(V)for break-junctions made of as-grown single-crystal Bi₂Sr₂CaCu₂O₈₊δ samples with Tc≈86-89 K was measured and clear-cut dip-hump structures (DHSs) were found in the range 80-120mV of the bias voltage V. The theory of tunneling in symmetric junctions between inhomogeneous charge-density-wave (CDW) superconductors, considered in the framework of the s-pairing model, has been developed. CDWs have been shown to be responsible for the appearance of the DHS in the tunnel current- voltage characteristics and properly describes experimental results