53,863 research outputs found
Spin-3/2 physics of semiconductor hole nanowires: Valence-band mixing and tunable interplay between bulk-material and orbital bound-state spin splittings
We present a detailed theoretical study of the electronic spectrum and Zeeman
splitting in hole quantum wires. The spin-3/2 character of the topmost
bulk-valence-band states results in a strong variation of subband-edge g
factors between different subbands. We elucidate the interplay between quantum
confinement and heavy-hole - light-hole mixing and identify a certain
robustness displayed by low-lying hole-wire subband edges with respect to
changes in the shape or strength of the wire potential. The ability to address
individual subband edges in, e.g., transport or optical experiments enables the
study of holes states with nonstandard spin polarization, which do not exist in
spin-1/2 systems. Changing the aspect ratio of hole wires with rectangular
cross-section turns out to strongly affect the g factor of subband edges,
providing an opportunity for versatile in-situ tuning of hole-spin properties
with possible application in spintronics. The relative importance of cubic
crystal symmetry is discussed, as well as the spin splitting away from
zone-center subband edges.Comment: 16 pages, 12 figures, RevTe
Pseudospin symmetry in supersymmetric quantum mechanics: Schr\"odinger equations
The origin of pseudospin symmetry (PSS) and its breaking mechanism are
explored by combining supersymmetry (SUSY) quantum mechanics, perturbation
theory, and the similarity renormalization group (SRG) method. The
Schr\"odinger equation is taken as an example, corresponding to the
lowest-order approximation in transforming a Dirac equation into a diagonal
form by using the SRG. It is shown that while the spin-symmetry-conserving term
appears in the single-particle Hamiltonian , the PSS-conserving term appears
naturally in its SUSY partner Hamiltonian . The eigenstates of
Hamiltonians and are exactly one-to-one identical except for
the so-called intruder states. In such a way, the origin of PSS deeply hidden
in can be traced in its SUSY partner Hamiltonian . The
perturbative nature of PSS in the present potential without spin-orbit term is
demonstrated by the perturbation calculations, and the PSS-breaking term can be
regarded as a very small perturbation on the exact PSS limits. A general
tendency that the pseudospin-orbit splittings become smaller with increasing
single-particle energies can also be interpreted in an explicit way.Comment: 31 pages, 11 figures, 2 table
Scaling property of ideal granitic sequences
Quantification of granite textures and structures using a mathematical model for characterization of granites has been a long-term attempt of mathematical geologists over the past four decades. It is usually difficult to determine the influence of magma properties on mineral crystallization forming fined-grained granites due to its irregular and fine-grained textures. The ideal granite model was originally developed for modeling mineral sequences from first and second-order Markov properties. This paper proposes a new model for quantifying scale invariance properties of mineral clusters and voids observed within mineral sequences. Sequences of the minerals plagioclase, quartz and orthoclase observed under the microscope for 104 aplite samples collected from the Meech Lake area, Gatineau Park, Québec were used for validation of the model. The results show that the multi-scale approaches proposed in this paper may enable quantification of the nature of the randomness of mineral grain distributions. This, in turn, may be related to original properties of the magma
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