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Correlated electron systems are highly susceptible to various forms of electronic order. By tuning the transition temperature towards absolute zero, striking deviations from conventional metallic (Fermi-liquid) behaviour can be realized. Evidence for electronic nematicity, a correlated electronic state with broken rotational symmetry, has been reported in a host of metallic systems.sup.1-5 that exhibit this so-called quantum critical behaviour. In all cases, however, the nematicity is found to be intertwined with other forms of order, such as antiferromagnetism.sup.5-7 or charge-density-wave order.sup.8, that might themselves be responsible for the observed behaviour. The iron chalcogenide FeSe.sub.1-xS.sub.x is unique in this respect because its nematic order appears to exist in isolation.sup.9-11, although until now, the impact of nematicity on the electronic ground state has been obscured by superconductivity. Here we use high magnetic fields to destroy the superconducting state in FeSe.sub.1-xS.sub.x and follow the evolution of the electrical resistivity across the nematic quantum critical point. Classic signatures of quantum criticality are revealed: an enhancement in the coefficient of the T.sup.2 resistivity (due to electron-electron scattering) on approaching the critical point and, at the critical point itself, a strictly T-linear resistivity that extends over a decade in temperature T. In addition to revealing the phenomenon of nematic quantum criticality, the observation of T-linear resistivity at a nematic critical point also raises the question of whether strong nematic fluctuations play a part in the transport properties of other 'strange metals', in which T-linear resistivity is observed over an extended regime in their respective phase diagrams. The pattern of electrical resistivity in an unconventional superconductor at high magnetic fields and low temperatures across the nematic quantum critical point reveals two classic signatures of quantum criticality., Author(s): S. Licciardello [sup.1] , J. Buhot [sup.1] , J. Lu [sup.1] , J. Ayres [sup.1] [sup.2] , S. Kasahara [sup.3] , Y. Matsuda [sup.3] , T. Shibauchi [sup.4] , [...]

The long-predicted suppression of quasiparticle dissipation in a Josephson junction when the phase difference across the junction is [pi] is inferred from a sharp maximum in the energy relaxation time of a superconducting artificial atom. Quasiparticle dissipation in a Josephson junction Josephson junctions, which consist of two superconductors connected by a weak link, have a central role in quantum electronic applications, such as in sensitive magnetic field detectors, high-speed processing and quantum information networks. However, a fundamental prediction concerning the Josephson effect has not yet been confirmed. It is known that the current flowing through a Josephson junction is made up from superconducting Cooper pairs as well as excitations called quasiparticles, which contribute in a few different ways. One contribution causes dissipation but can in theory be suppressed by tuning the phase difference between the superconductors. This has been achieved experimentally. Ioan Pop et al. have made a qubit comprising a Josephson junction. The energy relaxation time of this qubit increases by almost two orders of magnitude owing to the suppression of quasiparticle dissipation. This finding confirms the existence of a fundamental quantum phenomenon predicted over 50 years ago. Owing to the low-loss propagation of electromagnetic signals in superconductors, Josephson junctions constitute ideal building blocks for quantum memories, amplifiers, detectors and high-speed processing units, operating over a wide band of microwave frequencies. Nevertheless, although transport in superconducting wires is perfectly lossless for direct current, transport of radio-frequency signals can be dissipative in the presence of quasiparticle excitations above the superconducting gap.sup.1. Moreover, the exact mechanism of this dissipation in Josephson junctions has never been fully resolved experimentally. In particular, Josephson's key theoretical prediction that quasiparticle dissipation should vanish in transport through a junction when the phase difference across the junction is [pi] (ref. 2) has never been observed.sup.3. This subtle effect can be understood as resulting from the destructive interference of two separate dissipative channels involving electron-like and hole-like quasiparticles. Here we report the experimental observation of this quantum coherent suppression of quasiparticle dissipation across a Josephson junction. As the average phase bias across the junction is swept through [pi], we measure an increase of more than one order of magnitude in the energy relaxation time of a superconducting artificial atom. This striking suppression of dissipation, despite the presence of lossy quasiparticle excitations above the superconducting gap, provides a powerful tool for minimizing decoherence in quantum electronic systems and could be directly exploited in quantum information experiments with superconducting quantum bits., Author(s): Ioan M. Pop [sup.1] , Kurtis Geerlings [sup.1] , Gianluigi Catelani [sup.1] [sup.2] , Robert J. Schoelkopf [sup.1] , Leonid I. Glazman [sup.1] , Michel H. Devoret [sup.1] Author [...]

The gravitational field shielding by scalar field and type II superconductors are theoretically investigated. In accord with the well-developed five-dimensional fully covariant Kaluza-Klein theory with a scalar field, which unifies the Einsteinian general relativity and Maxwellian electromagnetic theory, the scalar field cannot only polarize the space as shown previously, but also flatten the space as indicated recently. The polarization of space decreases the electromagnetic field by increasing the equivalent vacuum permittivity constant, while the flattening of space decreases the gravitational field by decreasing the equivalent gravitational constant. In other words, the scalar field can be also employed to shield the gravitational field. A strong scalar field significantly shield the gravitational field by largely decreasing the equivalent gravitational constant. According to the theory of gravitational field shielding by scalar field, the weight loss experimentally detected for a sample near a rotating ceramic disk at very low temperature can be explained as the shielding of the Earth gravitational field by the Ginzburg-Landau scalar field, which is produced by the type II superconductors. The significant shielding of gravitational field by scalar field produced by superconductors may lead to a new spaceflight technology in future., 1 Introduction Gravitation is one of the four fundamental interactions of nature. According to the Newtonian universal law of gravitation, any two objects in the universe attract each other with [...]