2,929 research outputs found
Extension of the Adler-Bobenko-Suris classification of integrable lattice equations
The classification of lattice equations that are integrable in the sense of
higher-dimensional consistency is extended by allowing directed edges. We find
two cases that are not transformable via the 'admissible transformations' to
the lattice equations in the existing classification.Comment: 14 pages, 2 figure
Interface-induced heavy-hole/light-hole splitting of acceptors in silicon
The energy spectrum of spin-orbit coupled states of individual sub-surface
boron acceptor dopants in silicon have been investigated using scanning
tunneling spectroscopy (STS) at cryogenic temperatures. The spatially resolved
tunnel spectra show two resonances which we ascribe to the heavy- and
light-hole Kramers doublets. This type of broken degeneracy has recently been
argued to be advantageous for the lifetime of acceptor-based qubits [Phys. Rev.
B 88 064308 (2013)]. The depth dependent energy splitting between the heavy-
and light-hole Kramers doublets is consistent with tight binding calculations,
and is in excess of 1 meV for all acceptors within the experimentally
accessible depth range (< 2 nm from the surface). These results will aid the
development of tunable acceptor-based qubits in silicon with long coherence
times and the possibility for electrical manipulation
Simultaneous conduction and valence band quantisation in ultra-shallow, high density doping profiles in semiconductors
We demonstrate simultaneous quantisation of conduction band (CB) and valence
band (VB) states in silicon using ultra-shallow, high density, phosphorus
doping profiles (so-called Si:P -layers). We show that, in addition to
the well known quantisation of CB states within the dopant plane, the
confinement of VB-derived states between the sub-surface P dopant layer and the
Si surface gives rise to a simultaneous quantisation of VB states in this
narrow region. We also show that the VB quantisation can be explained using a
simple particle-in-a-box model, and that the number and energy separation of
the quantised VB states depend on the depth of the P dopant layer beneath the
Si surface. Since the quantised CB states do not show a strong dependence on
the dopant depth (but rather on the dopant density), it is straightforward to
exhibit control over the properties of the quantised CB and VB states
independently of each other by choosing the dopant density and depth
accordingly, thus offering new possibilities for engineering quantum matter.Comment: 5 pages, 2 figures and supplementary materia
Symmetry and Integrability of Non-Singlet Sectors in Matrix Quantum Mechanics
We study the non-singlet sectors of matrix quantum mechanics (MQM) through an
operator algebra which generates the spectrum. The algebra is a nonlinear
extension of the W_\infty algebra where the nonlinearity comes from the angular
part of the matrix which can not be neglected in the non-singlet sector. The
algebra contains an infinite set of commuting generators which can be regarded
as the conserved currents of MQM. We derive the spectrum and the eigenfunctions
of these conserved quantities by a group theoretical method. An interesting
feature of the spectrum of these charges in the non-singlet sectors is that
they are identical to those of the singlet sector except for the
multiplicities. We also derive the explicit form of these commuting charges in
terms of the eigenvalues of the matrix and show that the interaction terms
which are typical in Calogero-Sutherland system appear. Finally we discuss the
bosonization and rewrite the commuting charges in terms of a free boson
together with a finite number of extra degrees of freedom for the non-singlet
sectors.Comment: 34 pages, 4 figure
Mixing of Ground States in Vertex Models
We consider the analogue of the 6-vertex model constructed from alternating
spin n/2 and spin m/2 lines, where . We identify the transfer matrix
and the space on which it acts in terms of the representation theory of
. We diagonalise the transfer matrix and compute the S-matrix. We
give a trace formula for local correlation functions. When n=1, the 1-point
function of a spin m/2 local variable for the alternating lattice with a
particular ground state is given as a linear combination of the 1-point
functions of the pure spin m/2 model with different ground states. The mixing
ratios are calculated exactly and are expressed in terms of irreducible
characters of and the deformed Virasoro algebra.Comment: 12 pages, LaTeX, typos correcte
Impurity Operators in RSOS Models
We give a construction of impurity operators in the `algebraic analysis'
picture of RSOS models. Physically, these operators are half-infinite
insertions of certain fusion-RSOS Boltzmann weights. They are the face analogue
of insertions of higher spin lines in vertex models. Mathematically, they are
given in terms of intertwiners of modules. We present a
detailed perturbation theory check of the conjectural correspondence between
the physical and mathematical constructions in a particular simple example.Comment: Latex, 24 pages, uses amsmath, amsthm, amssymb, epic, eepic and
texdraw style files (Minor typos corrected) (minor changes
Quantum states and linear response in dc and electromagnetic fields for charge current and spin polarization of electrons at Bi/Si interface with giant spin-orbit coupling
An expansion of the nearly free-electron model constructed by Frantzeskakis,
Pons and Grioni [Phys. Rev. B {\bf 82}, 085440 (2010)] describing quantum
states at Bi/Si(111) interface with giant spin-orbit coupling is developed and
applied for the band structure and spin polarization calculation, as well as
for the linear response analysis for charge current and induced spin caused by
dc field and by electromagnetic radiation. It is found that the large
spin-orbit coupling in this system may allow resolving the spin-dependent
properties even at room temperature and at realistic collision rate. The
geometry of the atomic lattice combined with spin-orbit coupling leads to an
anisotropic response both for current and spin components related to the
orientation of the external field. The in-plane dc electric field produces only
the in-plane components of spin in the sample while both the in-plane and
out-of-plane spin components can be excited by normally propagating
electromagnetic wave with different polarizations.Comment: 10 pages, 9 figure
Stability of accretion disk around rotating black holes: a pseudo-general-relativistic fluid dynamical study
We discuss the solution of accretion disk when the black hole is chosen to be
rotating. We study, how the fluid properties get affected for different
rotation parameters of the black hole. We know that no cosmic object is static
in Universe. Here the effect of the rotation of the black hole to the
space-time is considered following an earlier work of the author, where the
pseudo-Newtonian potential was prescribed for the Kerr geometry. We show that,
with the inclusion of rotation of the black hole, the valid disk parameter
region dramatically changes and disk becomes unstable. Also we discuss about
the possibility of shock in accretion disk around rotating black holes. When
the black hole is chosen to be rotating, the sonic locations of the accretion
disk get shifted or disappear, making the disk unstable. To bring it in the
stable situation, the angular momentum of the accreting matter has to be
reduced/enhanced (for co/counter-rotating disk) by means of some physical
process.Comment: 24 Latex pages including 7 figures; Accepted for publication in
Astrophysical Journa
Generalised Perk--Schultz models: solutions of the Yang-Baxter equation associated with quantised orthosymplectic superalgebras
The Perk--Schultz model may be expressed in terms of the solution of the
Yang--Baxter equation associated with the fundamental representation of the
untwisted affine extension of the general linear quantum superalgebra
, with a multiparametric co-product action as given by
Reshetikhin. Here we present analogous explicit expressions for solutions of
the Yang-Baxter equation associated with the fundamental representations of the
twisted and untwisted affine extensions of the orthosymplectic quantum
superalgebras . In this manner we obtain generalisations of the
Perk--Schultz model.Comment: 10 pages, 2 figure
- …