Long-range ferromagnetic correlations between Anderson impurities in a semiconductor host

We study the two-impurity Anderson model for a semiconductor host using the quantum Monte Carlo technique. We find that the impurity spins exhibit ferromagnetic correlations with a range which can be much more enhanced than in a half-filled metallic band. In particular, the range is longest when the Fermi level is located above the top of the valence band and decreases as the impurity bound state becomes occupied. Comparisons with the photoemission and optical absorption experiments suggest that this model captures the basic electronic structure of Ga_{1-x}Mn_xAs, the prototypical dilute magnetic semiconductor (DMS). These numerical results might also be useful for synthesizing DMS or dilute-oxide ferromagnets with higher Curie temperatures.Comment: 4 pages, 4 figure

Classical Coulomb three-body problem in collinear eZe configuration

Classical dynamics of two-electron atom and ions H$^{-}$, He, Li$^{+}$, Be$^{2+}$,... in collinear eZe configuration is investigated. It is revealed that the mass ratio $\xi$ between necleus and electron plays an important role for dynamical behaviour of these systems. With the aid of analytical tool and numeircal computation, it is shown that thanks to large mass ratio $\xi$, classical dynamics of these systems is fully chaotic, probably hyperbolic. Experimental manifestation of this finding is also proposed.Comment: Largely rewritten. 21 pages. All figures are available in http://ace.phys.h.kyoto-u.ac.jp/~sano/3-body/index.htm

Sustainability in Selleck Food Court at the University of Nebraska-Lincoln

Our project proposes practical solutions for reducing food waste and improving student perceptions of food sustainability at the University of Nebraska-Lincoln (UNL). Our solutions are derived from undergraduate student survey responses and inspired by conversations with UNL Dining and Sustainable campus groups. We collected data from two hundred and six students and focused on students with meal plans who ate at Selleck Food Court. Within the qualitative response field, students could write suggestions for improvements to Selleck Food Court. These responses revealed common themes repeatedly raised by students who are passionate about and interested in dining sustainability, whether that is in recycling options, food waste consciousness, or education. Long-term culture building is valuable in dining to promote students’ sustainable behaviors. As our first main solution, we found that signage can act as a reminder, and influence students to be more conscious. In order for us to gain measurable progress, it takes diligent and routine programming to observe long-term cultural changes in the student population. Our second main solution is for the University of Nebraska-Lincoln to implement composting, specifically at Selleck Food Court. We found that students are already knowledgeable and willing to participate in composting. We acknowledge a limitation of this study was the potential self-selecting bias among the respondents. Our undergraduate student survey was advertised on around 118 bulletin boards within residence halls, within Selleck Food Court, through faculty, some academic buildings from the College of Arts and Sciences and online departmental newsletters. Respondents who are more inclined to participate in sustainable behavior may be more willing to engage in the study than students who feel indifferent towards the topic. Nonetheless, our aim was to broadly collect data and formulate solutions to the food sustainability efforts at Selleck Food Court

Superconducting pi qubit with a ferromagnetic Josephson junction

Solid-state qubits have the potential for the large-scale integration and for the flexibility of layout for quantum computing. However, their short decoherence time due to the coupling to the environment remains an important problem to be overcome. We propose a new superconducting qubit which incorporates a spin-electronic device: the qubit consists of a superconducting ring with a ferromagnetic pi junction which has a metallic contact and a normal Josephson junction with an insulating barrier. Thus, a quantum coherent two-level state is formed without an external magnetic field. This feature and the simple structure of the qubit make it possible to reduce its size leading to a long decoherence time.Comment: 4 pages, 3 figure

Graphene as a buffer layer for silicon carbide-on-insulator structures

We report an innovative technique for growing the silicon carbide-on-insulator (SiCOI) structure by utilizing polycrystalline single layer graphene (SLG) as a buffer layer. The epitaxial growth was carried out using a hot-mesh chemical vapor deposition (HM-CVD) technique. Cubic SiC (3C-SiC) thin film in (111) domain was realized at relatively low substrate temperature of 750 °C. 3C-SiC energy bandgap of 2.2 eV was confirmed. The Si-O absorption band observed in the grown film can be caused by the out-diffusion of the oxygen atom from SiO2 substrate or oxygen doping during the cleaning process. Further experimental works by optimizing the cleaning process, growth parameters of the present growth method, or by using other growth methods, as well, are expected to realize a high quality SiCOI structure, thereby opening up the way for a breakthrough in the development of advanced ULSIs with multifunctionalities