Featured in EPL
Most recent highlights from EPL:
Symmetry detection of auxetic behaviour in 2D frameworks1
by H. Mitschke, G. E. Schröder-Turk, K. Mecke, P. W. Fowler and S. D. Guest
A symmetry-extended Maxwell treatment of the net mobility of periodic bar-and-joint frameworks is used to derive a sufficient condition for auxetic behaviour of a 2D material. The type of auxetic behaviour that can be detected by symmetry has Poisson’s ratio −1, with equal expansion/contraction in all directions, and is here termed equiauxetic. A framework may have a symmetry-detectable equiauxetic mechanism if it belongs to a plane group that includes rotational axes of order n = 6, 4, or 3. If the reducible representation for the net mobility contains mechanisms that preserve full rotational symmetry (A modes), these are equiauxetic. In addition, for n = 6, mechanisms that halve rotational symmetry (B modes) are also equiauxetic.
Electron pockets and pseudogap asymmetry observed in the thermopower of underdoped cuprates2
by J. G. Storey, J. L. Tallon and G. V. M. Williams
We calculate the diffusion thermoelectric power of high- Tc cuprates using the resonating-valence-bond spin-liquid model developed by Yang, Rice and Zhang (YRZ). In this model, reconstruction of the energy-momentum dispersion results in a pseudogap in the density of states that is heavily asymmetric about the Fermi level. The subsequent asymmetry in the spectral conductivity is found to account for the large magnitude and temperature dependence of the thermopower observed in underdoped cuprates. In addition we find evidence in experimental data for electron pockets in the Fermi surface, arising from a YRZ-like reconstruction, near the onset of the pseudogap in the slightly overdoped regime.
Dynamic jamming fronts 3
by S. R. Waitukaitis, L. K. Roth, V. Vitelli and H. M. Jaeger
We describe a model experiment for dynamic jamming: a two-dimensional collection of initially unjammed disks that are forced into the jammed state by uniaxial compression via a rake. This leads to a stable densification front that travels ahead of the rake, leaving regions behind it jammed. Using disk conservation in conjunction with an upper limit to the packing fraction at jamming onset, we predict the front speed as a function of packing fraction and rake speed. However, we find that the jamming front has a finite width, a feature that cannot be explained by disk conservation alone. This width appears to diverge on approach to jamming, which suggests that it may be related to growing lengthscales encountered in other jamming studies.
- H. Mitschke, G. E. Schröder-Turk, K. Mecke, P. W. Fowler and S. D. Guest. 2013. Symmetry detection of auxetic behaviour in 2D frameworks. EPL, 102, 66005. DOI: 10.1209/0295-5075/102/66005 [↩]
- J. G. Storey, J. L. Tallon and G. V. M. Williams. 2013. Electron pockets and pseudogap asymmetry observed in the thermopower of underdoped cuprates. EPL, 102, 37006. DOI: 10.1209/0295-5075/102/37006 [↩]
- S. R. Waitukaitis, L. K. Roth, V. Vitelli and H. M. Jaeger. 2013. Dynamic jamming fronts . EPL, 102, 44001. DOI: 10.1209/0295-5075/102/44001 [↩]
