Simulating metric signature effects with metamaterials

A funny work here.

We demonstrate that the extraordinary waves in indefinite metamaterials experience an effective metric signature. During a metric signature change transition in such a metamaterial, a Minkowski space-time is created together with a large number of particles populating the space-time. Such metamaterial models provide a tabletop realization of metric signature change events suggested to occur in Bose-Einstein condensates and quantum gravity theories.

real-time tracking the motions of electrons

Atto-second spectroscopy enables this !

doi:10.1038/nature09212

Attosecond technology (1 as=10⁻¹⁸ S) promises the tools needed to directly probe electron motion in real time. These authors report attosecond pump–probe measurements that track the movement of valence electrons in krypton ions. This first proof-of-principle demonstration uses a simple system, but the expectation is that attosecond transient absorption spectroscopy will ultimately also reveal the elementary electron motions that underlie the properties of molecules and solid-state materials.

This is a rather funny and informative video

http://www.youtube.com/watch?v=GxXWpiDd_7c&feature=player_embedded

Through the years leading to the discovery of BCS theory

Almost half a century passed between the discovery of superconductivity by Kammerlingh Onnes and the theoretical explanation of the phenomenon by Bardeen, Cooper and Schrieffer. During the intervening years the brightest minds in theoretical physics tried and failed to develop a microscopic understanding of the effect. A summary of some of those unsuccessful attempts to understand superconductivity not only demonstrates the extraordinary achievement made by formulating the BCS theory, but also illustrates that mistakes are a natural and healthy part of the scientific discourse, and that inapplicable, even incorrect theories can turn out to be interesting and inspiring.

http://arxiv.org/ftp/arxiv/papers/1008/1008.0447.pdf

nodes found of the paring gap in pnictides

The thermal conductivity of the iron-arsenide superconductor Ba Fe1−xCox 2As2 was measured down to 50 mK for a heat current parallel c and perpendicular a to the tetragonal c axis for seven Co concentrations from underdoped to overdoped regions of the phase diagram 0.038 x 0.127 . A residual linear term c0 /T is observed in the T→0 limit when the current is along the c axis, revealing the presence of nodes in the gap. Because the nodes appear as x moves away from the concentration of maximal Tc, they must be accidental, not imposed by symmetry, and are therefore compatible with an s state, for example. The fact that the in-plane residual linear term a0 /T is negligible at all x implies that the nodes are located in regions of the Fermi surface that contribute strongly to c-axis conduction and very little to in-plane conduction. Application of a moderate magnetic field e.g., Hc2 /4 excites quasiparticles that conduct heat along the a axis just as well as the nodal
quasiparticles conduct along the c axis. This shows that the gap must be very small but nonzero in regions of the Fermi surface which contribute significantly to in-plane conduction. These findings can be understood in terms of a strong k dependence of the gap k which produces nodes on a Fermi-surface sheet with pronounced
c-axis dispersion and deep minima on the remaining, quasi-two-dimensional sheets.

PHYSICAL REVIEW B 82, 064501 2010

Phonon electron coupling in HTSC as seen recently

To observe the dynamics of electrons and phonons in a high-T_c superconductor, Pashkin et al. used a pump-probe technique. (Top) The first laser pulse excites an electron above the superconducting gap, while a second pulse in the THz range, reflected from the sample at variable delay τ, probes the gap. As time progresses, the superconducting gap closes and then opens again as indicated in the THz reflectivity. (Bottom) Simultaneously with the electron excitation, lattice vibrations of oxygen atoms in the YBCO are probed by watching how the center frequency and asymmetry of the line shape of the reflected light changes with time. Surprisingly, the electrons and photons are excited and decay on the same time scale, suggesting that the dynamics of the two species are to some degree independent.

Phys. Rev. Lett. 105, 067001 (2010)

F A Wilczek in this interview

He is good-natured, funny and thought to be among the smartest men in physics: Frank A. Wilczek, 58, a professor at the Massachusetts Institute of Technology who was one of three winners of the 2004 Nobel Prize in Physics. The award came for work Dr. Wilczek had done in his 20s, with David Gross of Princeton, on quantum chromodynamics, a theoretical advance that is part of the foundation of modern physics. Here is an edited version of two conversations with Dr. Wilczek, in October and this month.

Find the link here