1,232 research outputs found
Phonon emission and absorption in the fractional quantum Hall effect
We investigate the time dependent thermal relaxation of a two-dimensional
electron system in the fractional quantum Hall regime where ballistic phonons
are used to heat up the system to a non-equilibrium temperature. The thermal
relaxation of a 2DES at can be described in terms of a broad band
emission of phonons, with a temperature dependence proportional to . In
contrast, the relaxation at fractional filling is characterized by
phonon emission around a single energy, the magneto-roton gap. This leads to a
strongly reduced energy relaxation rate compared to with only a weak
temperature dependence for temperatures 150 mK 400 mK.Comment: 4 pages, 3 figures; 14th International Conference on High Magnetic
Fields in Semiconductor Physics, September 24-29, 2000, Matsue, Japa
Developing a program for pre-service teachers interested in teaching young female students in rural areas of developing countries
This capstone examines how training programs for pre-service teachers interested in teaching children in developing countries could be developed at the California State University (CSU) system level. Currently, there are few programs in place for teachers interested in teaching in developing countries. In order to teach abroad, they need to work for the Peace Corps or teach English in Korea, but training programs for pre-service teachers have not been institutionalized at the Institutions of Higher Learning (IHEs), such as CSU system. Teaching abroad usually creates a stigma for those who teach abroad and return to the United States, for one their experience is undervalued or distrusted. Through use of extensive literature review, a survey of Liberal Studies students and interview with an International Programs Manager at California State University Monterey Bay, this capstone examines the potential necessary elements of a training program for pre-service teachers interested in teaching in rural areas of developing countries at the CSU system
Aufbau und Entwicklung eines Bewertungssystems zur Beurteilung von Pferdehaltungen hinsichtlich Tiergerechtheit und Umweltwirkungen
A current research project at the Technical University Munich-Weihenstephan evaluates an integral on-farm welfare assessment system for horse husbandries. It is based on national animal welfare standard and does take sustainability into - system includes animal-based indicators as well as resource-based indicators. It is
stipulated that indicators are valid, reliable and feasible. Potential indicators were selected by study of literature and two field tests (30 horse husbandries, 1572 horses)
in order to examine reliability and feasibility. The welfare assessment system aims at objective and scientific-founded indicators that are both applicable for conventional
and ecological horse husbandries
Quantum-Hall activation gaps in graphene
We have measured the quantum-Hall activation gaps in graphene at filling
factors and for magnetic fields up to 32 T and temperatures
from 4 K to 300 K. The gap can be described by thermal excitation to
broadened Landau levels with a width of 400 K. In contrast, the gap measured at
is strongly temperature and field dependent and approaches the expected
value for sharp Landau levels for fields T and temperatures
K. We explain this surprising behavior by a narrowing of the lowest Landau
level.Comment: 4 pages, 4 figures, updated version after review, accepted for PR
Band inversion driven by electronic correlations at the (111) LaAlO/SrTiO interface
Quantum confinement at complex oxide interfaces establishes an intricate
hierarchy of the strongly correlated -orbitals which is widely recognized as
a source of emergent physics. The most prominent example is the (001)
LaAlO/SrTiO(LAO/STO) interface, which features a dome-shaped phase
diagram of superconducting critical temperature and spin-orbit coupling (SOC)
as a function of electrostatic doping, arising from a selective occupancy of
orbitals of different character. Here we study (111)-oriented LAO/STO
interfaces - where the three orbitals contribute equally to the
sub-band states caused by confinement - and investigate the impact of this
unique feature on electronic transport. We show that transport occurs through
two sets of electron-like sub-bands, and the carrier density of one of the sets
shows a non-monotonic dependence on the sample conductance. Using tight-binding
modeling, we demonstrate that this behavior stems from a band inversion driven
by on-site Coulomb interactions. The balanced contribution of all
orbitals to electronic transport is shown to result in strong SOC with reduced
electrostatic modulation.Comment: 5 pages, 4 figures, (+ supplemental material
Field-induced insulating states in a graphene superlattice
We report on high-field magnetotransport (B up to 35 T) on a gated
superlattice based on single-layer graphene aligned on top of hexagonal boron
nitride. The large-period moir\'e modulation (15 nm) enables us to access the
Hofstadter spectrum in the vicinity of and above one flux quantum per
superlattice unit cell (Phi/Phi_0 = 1 at B = 22 T). We thereby reveal, in
addition to the spin-valley antiferromagnet at nu = 0, two insulating states
developing in positive and negative effective magnetic fields from the main nu
= 1 and nu = -2 quantum Hall states respectively. We investigate the field
dependence of the energy gaps associated with these insulating states, which we
quantify from the temperature-activated peak resistance. Referring to a simple
model of local Landau quantization of third generation Dirac fermions arising
at Phi/Phi_0 = 1, we describe the different microscopic origins of the
insulating states and experimentally determine the energy-momentum dispersion
of the emergent gapped Dirac quasi-particles
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