70 research outputs found
Microscopic Mechanism of the Helix-to-Layer Transformation in Elemental Group VI Solids
We study the conversion of bulk Se and Te, consisting of intertwined a
helices, to structurally very dissimilar, atomically thin two-dimensional (2D)
layers of these elements. Our ab initio calculations reveal that previously
unknown and unusually stable \delta - and \eta-2D allotropes may form in an
intriguing multi-step process that involves a concerted motion of many atoms at
dislocation defects. We identify such a complex reaction path involving
zipper-like motion of such dislocations that initiate structural changes. With
low activation barriers <0.3 eV along the optimum path, the conversion process
may occur at moderate temperatures. We find all one-dimensional (1D) and 2D
chalcogen structures to be semiconducting.Comment: accepted by Nano Letter
Moir\'{e} effects in graphene--hBN heterostructures
Encapsulating graphene in hexagonal Boron Nitride has several advantages: the
highest mobilities reported to date are achieved in this way, and precise
nanostructuring of graphene becomes feasible through the protective hBN layers.
Nevertheless, subtle effects may arise due to the differing lattice constants
of graphene and hBN, and due to the twist angle between the graphene and hBN
lattices. Here, we use a recently developed model which allows us to perform
band structure and magnetotransport calculations of such structures, and show
that with a proper account of the moir\'e physics an excellent agreement with
experiments can be achieved, even for complicated structures such as disordered
graphene, or antidot lattices on a monolayer hBN with a relative twist angle.
Calculations of this kind are essential to a quantitative modeling of
twistronic devices
Coherence and complementarity based on modified generalized skew information
We introduce modified generalized Wigner-Yanase-Dyson (MGWYD) skew
information and modified weighted generalized Wigner-Yanase-Dyson (MWGWYD) skew
information. By revisiting state-channel interaction based on MGWYD skew
information, a family of coherence measures with respect to quantum channels is
proposed. Furthermore, explicit analytical expressions of these coherence
measures of qubit states are derived with respect to different quantum
channels. Moreover, complementarity relations based on MGWYD skew information
and MWGWYD skew information are also presented. Specifically, the conservation
relations are investigated, while two interpretations of them including
symmetry-asymmetry complementarity and wave-particle duality have been
proposed.Comment: 20page
Average skew information-based coherence and its typicality for random quantum states
We study the average skew information-based coherence for both random pure
and mixed states. The explicit formulae of the average skew information-based
coherence are derived and shown to be the functions of the dimension N of the
state space. We demonstrate that as N approaches to infinity, the average
coherence is 1 for random pure states, and a positive constant less than 1/2
for random mixed states. We also explore the typicality of average skew
information-based coherence of random quantum states. Furthermore, we identify
a coherent subspace such that the amount of the skew information-based
coherence for each pure state in this subspace can be bounded from below almost
always by a fixed number that is arbitrarily close to the typical value of
coherence.Comment: 24page
Uncertainty Relations Based on Modified Wigner-Yanase-Dyson Skew Information
Uncertainty relation is a core issue in quantum mechanics and quantum
information theory. We introduce modified generalized Wigner-Yanase-Dyson
(MGWYD) skew information and modified weighted generalizedWigner-Yanase-Dyson
(MWGWYD) skew information, and establish new uncertainty relations in terms of
the MGWYD skew information and MWGWYD skew information.Comment: 16 page
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