Ferroelectric Exchange Bias Affects Interfacial Electronic States

In polar oxide interfaces phenomena such as superconductivity, magnetism, 1D conductivity, and quantum Hall states can emerge at the polar discontinuity. Combining controllable ferroelectricity at such interfaces can affect the superconducting properties and sheds light on the mutual effects between the polar oxide and the ferroelectric oxide. Here, the interface between the polar oxide LaAlO₃ and the ferroelectric Ca-doped SrTiO₃ is studied by means of electrical transport combined with local imaging of the current flow with the use of scanning a superconducting quantum interference device (SQUID). Anomalous behavior of the interface resistivity is observed at low temperatures. The scanning SQUID maps of the current flow suggest that this behavior originates from an intrinsic bias induced by the polar LaAlO₃ layer. Such intrinsic bias combined with ferroelectricity can constrain the possible structural domain tiling near the interface. The use of this intrinsic bias is recommended as a method of controlling and tuning the initial state of ferroelectric materials by the design of the polar structure. The hysteretic dependence of the normal and the superconducting state properties on gate voltage can be utilized in multifaceted controllable memory devices.     

Unconventional pairing in doped band insulators on a honeycomb lattice: the role of the disconnected Fermi surface and a possible application to superconducting β-MNCl (M=Hf,Zr)

Abstract

We investigate the possibility of realizing unconventional superconductivity in doped band insulators on the square and honeycomb lattices. The latter lattice is found to be a good candidate due to the disconnectivity of the Fermi surface. We propose applying the theory to the superconductivity in doped layered nitride β-MNCl (M= Hf, Zr). Finally, we compare two groups of superconductors with disconnected Fermi surface, β-MNCl and the iron pnictides, which have high critical temperature T_c, despite some faults against superconductivity are present.     

Effect of Th doping on superconductivity in CePt3Si

Alloys from the solid solution Ce_1−xTh_xPt₃Si (x = 0.0, 0.02, 0.04, 0.08, 0.1, 0.2 and 1.0) were prepared by arc-melting. X-ray Rietveld powder analyses revealed that alloys in the compositional range 0 ≤ x ≤ 0.2 crystallize with the CePt₃B-type with a random distribution of Ce and Th atoms in positions 1(b) (1/2, 1/2, z) of the noncentrosymmetric space group P4mm. Th-doping results in a rapid suppression of the superconductivity. The alloy with x = 0.02 shows the onset of superconducting state at T_c = 400 mK, while that with x = 0.04 remains in normal metallic state at least down to 70 mK.     

The London–Anderson–Englert–Brout–Higgs–Guralnik–Hagen–Kibble–Weinberg mechanism and Higgs boson reveal the unity and future excitement of physics

The particle recently discovered by the CMS and ATLAS collaborations at CERN is almost certainly a Higgs boson, fulfilling a quest that can be traced back to three seminal high-energy papers of 1964, but which is intimately connected to ideas in other areas of physics that go back much further. One might oversimplify the history of the features which (i) give mass to the W and Z particles that mediate the weak nuclear interaction, (ii) effectively break gauge invariance, (iii) eliminate physically unacceptable Nambu–Goldstone bosons, and (iv) give mass to fermions (like the electron) by collectively calling them the London–Anderson–Englert–Brout–Higgs–Guralnik–Hagen–Kibble–Weinberg mechanism. More important are the implications for the future: a Higgs boson appears to point toward supersymmetry, since new physics is required to protect its mass from enormous quantum corrections, while the discovery of neutrino masses seems to point toward grand unification of the non-gravitational forces.     

Venturi tube application in high power test of the SRF module

In the superconducting RF module, the dissipation power of the niobium cavity is an important parameter. In the Superconducting radio frequency (SRF) module’s acceptance test at Shanghai Synchrotron Radiation Facility (SSRF), the Venturi tube is used to measure the quality factor of SRF cavity at 4.2 K. During the test, the venturi tube is be calibrated by increasing heat load with internal heater. In this paper, the horizontal test principle and venturi effect are briefly introduced. The authors find out a...     

Charge Stripes and Superconductivity in La2−x Ba x CuO4 and La1.6−x Nd0.4Sr x CuO4

We report x-ray scattering study of charge density wave (stripe) order in La_2−x Ba _x CuO₄ (LBCO) and La_1.6−x Nd_0.4Sr _x CuO₄ (LNSCO). The doping dependence of the charge stripe ordering temperature and the low-temperature correlation length is compared with the bulk superconducting transition temperature. We find that the charge stripe ordering temperature and correlation length are quite different in these two families of cuprates, while there seems to be inverse correlation between the bulk superconducting temperature and the charge stripe correlation length.     

A nontrivial factor in determining current distribution in an ac HTS cable-proximity effect

A superconductor has zero resistance at the superconducting state. This unique property creates many exceptional phenomena, of which some are known and the others are not. Our experiments with multilayer high temperature superconductor (HTS) cable samples revealed a new phenomenon that alternating current had a tendency to flow in the inner and outer layers of the cables. We attribute the cause of this phenomenon to the electromagnetic interaction in an infinite electrical conductivity medium and term it su...