Topological superconducting phases in disordered quantum wires with strong spin-orbit coupling

Zeeman fields can drive semiconductor quantum wires with strong spin-orbit coupling and in proximity to s-wave superconductors into a topological phase which supports end Majorana fermions and offers an attractive platform for realizing topological quantum information processing. Here, we investigate how potential disorder affects the topological phase by a combination of analytical and numerical approaches. Most prominently, we find that the robustness of the topological phase against disorder depends sensitively and non-monotonously on the Zeeman field applied to the wire.Comment: 6 pages, 3 figures; published versio

Higher return to pre-injury type of sports after revision anterior ligament reconstruction with lateral extra-articular tenodesis compared to without lateral extra-articular tenodesis

PurposeTo evaluate the rate of return to pre-injury type of sports (RTS type) in patients after revision anterior cruciate ligament reconstruction (ACLR) with lateral extra-articular tenodesis (LET) compared to patients after revision ACLR without LET.MethodsSeventy-eight patients who underwent revision ACLR with an autologous ipsilateral bone-patellar tendon-bone autograft with and without LET were included at least one year after surgery (mean follow-up: 43.9, SD: 29.2 months). All patients filled in a questionnaire about RTS type, the Knee injury and Osteoarthritis Outcome Score (KOOS), the International Knee Documentation Committee subjective form (IKDCsubjective), and the Tegner activity score.ResultsThe RTS type for revision ACLR with LET was 22 of 42 (52%), whereas 11 of 36 (31%) of the patients who underwent revision ACLR without LET returned to the pre-injury type of sport (p = 0.05). No significant differences were found in KOOS subscores, IKDCsubjective, and Tegner activity scores.ConclusionAn additional LET increases the rate of RTS type after revision ACLR

Spontaneous Emission in Chaotic Cavities

The spontaneous emission rate \Gamma of a two-level atom inside a chaotic cavity fluctuates strongly from one point to another because of fluctuations in the local density of modes. For a cavity with perfectly conducting walls and an opening containing N wavechannels, the distribution of \Gamma is given by P(\Gamma) \propto \Gamma^{N/2-1}(\Gamma+\Gamma_0)^{-N-1}, where \Gamma_0 is the free-space rate. For small N the most probable value of \Gamma is much smaller than the mean value \Gamma_0.Comment: 4 pages, RevTeX, 1 figur

Quantum dots based on spin properties of semiconductor heterostructures

The possibility of a novel type of semiconductor quantum dots obtained by spatially modulating the spin-orbit coupling intensity in III-V heterostructures is discussed. Using the effective mass model we predict confined one-electron states having peculiar spin properties. Furthermore, from mean field calculations (local-spin-density and Hartree-Fock) we find that even two electrons could form a bound state in these dots.Comment: 9 pages, 3 figures. Accepted in PRB (Brief Report) (2004

The galaxy environment in GAMA G3C groups using the Kilo Degree Survey Data Release 3

We aim to investigate the galaxy environment in GAMA Galaxy Groups Catalogue (G3C) using a volume-limited galaxy sample from the Kilo Degree Survey Data Release 3. The k-Nearest Neighbour technique is adapted to take into account the probability density functions (PDFs) of photometric redshifts in our calculations. This algorithm was tested on simulated KiDS tiles, showing its capability of recovering the relation between galaxy colour, luminosity and local environment. The characterization of the galaxy environment in G3C groups shows systematically steeper density contrasts for more massive groups. The red galaxy fraction gradients in these groups is evident for most of group mass bins. The density contrast of red galaxies is systematically higher at group centers when compared to blue galaxy ones. In addition, distinct group center definitions are used to show that our results are insensitive to center definitions. These results confirm the galaxy evolution scenario which environmental mechanisms are responsible for a slow quenching process as galaxies fall into groups and clusters, resulting in a smooth observed colour gradients in galaxy systems.Comment: 14 pages, Accepted to MNRA

Reflection of light from a disordered medium backed by a phase-conjugating mirror

This is a theoretical study of the interplay of optical phase-conjugation and multiple scattering. We calculate the intensity of light reflected by a phase-conjugating mirror when it is placed behind a disordered medium. We compare the results of a fully phase-coherent theory with those from the theory of radiative transfer. Both methods are equivalent if the dwell time \tau_{dwell} of a photon in the disordered medium is much larger than the inverse of the frequency shift 2\Delta\omega acquired at the phase-conjugating mirror. When \tau_{dwell} \Delta\omega < 1, in contrast, phase coherence drastically affects the reflected intensity. In particular, a minimum in the dependence of the reflectance on the disorder strength disappears when \Delta\omega is reduced below 1/\tau_{dwell}. The analogies and differences with Andreev reflection of electrons at the interface between a normal metal and a superconductor are discussed.Comment: 27 pages RevTeX with 11 figures included with psfi

Different carbon isotope fractionation patterns during the development of phototrophic freshwater and marine biofilms

Natural phototrophic biofilms are influenced by a broad array of abiotic and biotic factors and vary over temporal and spatial scales. Different developmental stages can be distinguished and growth rates will vary due to the thickening of the biofilm, which is expected to lead to a limitation of light or mass transport. This study shows that variation in CO&lt;sub&gt;2(aq)&lt;/sub&gt; availability leads to a fractionation shift and thereby affects &amp;delta;&lt;sup&gt;13&lt;/sup&gt;C signatures during biofilm development. For phototrophic freshwater biofilms it was found that the &amp;delta;&lt;sup&gt;13&lt;/sup&gt;C value became less negative with the thickening of the biofilm, while the opposite trend was found in marine biofilms. Modeling and pH profiling indicated that the trend in the freshwater system was caused by an increase in CO&lt;sub&gt;2(aq)&lt;/sub&gt; limitation resulting in an increase of HCO&lt;sub&gt;3&lt;/sub&gt;&lt;sup&gt;&amp;minus;&lt;/sup&gt; as C-source. The opposite trend in the marine system could be explained by a higher heterotrophic biomass and activity causing a higher carbon recycling and thereby lower &amp;delta;&lt;sup&gt;13&lt;/sup&gt;C values. We conclude that &amp;delta;&lt;sup&gt;13&lt;/sup&gt;C was more related to the net areal photosynthesis rate and carbon recycling, rather than to the growth rate of the biofilms

Reconfigurable Photonic Crystal Cavities

Photonic crystals are optical structures that contain a periodic modulation of their refractive index, allowing them to control light in recent years of an unprecedented capacity. Photonic crystals may take on a variety of configurations, in particular the photonic crystal cavity, which may “hold” light in small volumes comparable to the light’s wavelength. This capability to spatially confine light opens up countless possibilities to explore for research in telecommunications, quantum electrodynamics experiments and high-resolution sensor applications. However, the vast functionality potentially made available by photonic crystal cavities is limited due to the difficulty in redefining photonic crystal components once they are formed in their (typically) solid material. The work presented in this thesis investigates several approaches to overcome this issue by reconfiguring photonic crystal cavities