39 research outputs found
Anomalous Scaling in Heteroepitaxial Island Dynamics on Ag(100)
Diffusion and decay of alloyed Cu=Ag islands are investigated in the size range from 1 to 40 nm2 on Ag(100) at room temperature with fast-scanning tunneling microscopy and density functional theory. While islands at sizes above 7 nm2 show the diffusion and decay behavior expected for dynamics based on single atom hopping, islands smaller than 4 nm2 diffuse faster and decay slower than predicted by standard theory. This anomalous behavior at unexpected large island sizes is related to a size dependent dealloying of the Cu=Ag islands
Local determination of the amount of integration of an atom into a crystal surface
Collective vibrational modes of crystal lattices, called phonons, determine fundamental material properties, such as their thermal and electrical conductivities. Bulk phonon spectra are influenced by point defects. More recently, the importance of phonons on nanostructures has come into the focus of attention. Here we show a spatially resolved phonon spectra of point defects that reveal distinctly different signatures for a cavity alone and an impurity atom fully integrated into the surface as opposed to one placed into a cavity. The spectra are indicative for delocalized phonons and localized vibrations, respectively, as confirmed by theory
Non-Fermi liquid behavior with and without quantum criticality in Ce(1-x)Yb(x)CoIn(5)
One of the greatest challenges to Landau's Fermi liquid theory - the standard
theory of metals - is presented by complex materials with strong electronic
correlations. In these materials, non-Fermi liquid transport and thermodynamic
properties are often explained by the presence of a continuous quantum phase
transition which happens at a quantum critical point (QCP). A QCP can be
revealed by applying pressure, magnetic field, or changing the chemical
composition. In the heavy-fermion compound CeCoIn, the QCP is assumed to
play a decisive role in defining the microscopic structure of both normal and
superconducting states. However, the question of whether QCP must be present in
the material's phase diagram to induce non-Fermi liquid behavior and trigger
superconductivity remains open. Here we show that the full suppression of the
field-induced QCP in CeCoIn by doping with Yb has surprisingly little
impact on both unconventional superconductivity and non-Fermi liquid behavior.
This implies that the non-Fermi liquid metallic behavior could be a new state
of matter in its own right rather then a consequence of the underlying quantum
phase transition.Comment: 7 pages, 5 figure
A long view of liberal peace and its crisis
The ‘crisis’ of liberal peace has generated considerable debate in International Relations. However, analysis is inhibited by a shared set of spatial, cultural and temporal assumptions that rest on and reproduce a problematic separation between self-evident ‘liberal’ and ‘non-liberal’ worlds, and locates the crisis in presentist terms of the latter’s resistance to the former’s expansion. By contrast, this article argues that efforts to advance liberal rule have always been interwoven with processes of alternative order-making, and in this way are actively integral, not external, to the generation of the subjectivities, contestations, violence and rival social orders that are then apprehended as self-evident obstacles and threats to liberal peace and as characteristic of its periphery. Making visible these intimate relations of co-constitution elided by representations of liberal peace and its crisis requires a long view and an analytical frame that encompasses both liberalism and its others in the world. The argument is developed using a Foucauldian governmentality framework and illustrated with reference to Sri Lanka
Interplay of Superconductivity, Antiferromagnetism, and Pauli Depairing in CeCoIn
Low temperature magnetization M measurements down to 70~mK have been
performed through the superconducting upper critical field H_c2 of CeCoIn5 with
the field H parallel to the c axis of the tetragonal crystal. The crossing
through the upper critical field H_c2(0) is marked by a sign change in the
temperature dependence of M(T). A Fermi liquid law of the magnetization is
observed in the superconducting phase while in the paramagnetic state above
H_c2 a quasi-linear temperature dependence is obeyed. The specific heat below
H_c2 is therefor dominated by the increase of \gamma (H), the linear term of
the specific heat, and is marked by a singularity at H_{c2} (0). No indication
of the so called Q-phase was observed below H_c2 (in contrast to the case with
H applied in the basal plane).Comment: 4 pages, 5 figure