3,143 research outputs found
Observing the Berry phase in diffusive conductors: Necessary conditions for adiabaticity
In a recent preprint (cond-mat/9803170), van~Langen, Knops, Paasschens and
Beenakker attempt to re-analyze the proposal of Loss, Schoeller and Goldbart
(LSG) [Phys. Rev. B~48, 15218 (1993)] concerning Berry phase effects in the
magnetoconductance of diffusive systems. Van Langen et al. claim that the
adiabatic approximation for the Cooperon previously derived by LSG is not valid
in the adiabatic regime identified by LSG. It is shown that the claim of
van~Langen et al. is not correct, and that, on the contrary, the
magnetoconductance does exhibit the Berry phase effect within the LSG regime of
adiabaticity. The conclusion reached by van~Langen et al. is based on a
misinterpretation of field-induced dephasing effects, which can mask the Berry
phase (and any other phase coherent phenomena) for certain parameter values.Comment: 25 pages, 9 figure
Use of entanglement in quantum optics
Several recent demonstrations of two-particle interferometry are reviewed and shown to be examples of either color entanglement or beam entanglement. A device, called a number filter, is described and shown to be of value in preparing beam entanglements. Finally, we note that all three concepts (color and beam entaglement, and number filtering) may be extended to three or more particles
On the nature of national involvement: a preliminary study
Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/67978/2/10.1177_002200276901300303.pd
Chiral 1D Floquet topological insulators beyond rotating wave approximation
We study one-dimensional (1D) Floquet topological insulators with chiral
symmetry going beyond the standard rotating wave approximation. The occurrence
of many anticrossings between Floquet replicas leads to a dramatic extension of
phase diagram regions with stable topological edge states (TESs). We present an
explicit construction of all TESs in terms of a truncated Floquet Hamiltonian
in frequency space, prove the bulk-boundary correspondence, and analyze the
stability of the TESs in terms of their localization lengths. We propose
experimental tests of our predictions in curved bilayer graphene.Comment: 4+9 page
Magnetotransport in anisotropic Pb films and monolayers
The anisotropy induced by atomic steps of a Si(557) substrate in structure and magnetoconductance of ultrathin Pb films adsorbed on this surface is shown to be effectively shielded as a function of layer thickness, as found out by a combined study of low-energy electron diffraction and macroscopic four-point conductivity measurements as a function of Pb coverage, temperature, and magnetic field. In strong contrast to flat Si(111), substrate steps effectively compensate the lateral misfit (10%), leading to crystalline growth starting from the first monolayer. Multilayers already exceeding four physical monolayers (PML) form isotropic and percolated Pb islands even on this uniaxial surface. This structural anisotropy corresponds well to that found in dc conductivity measurements. As a function of temperature, strong localization effects with clear anisotropy become dominant for coverages below 4 PML. Strong anisotropic magnetotransport was found for Pb-wetting layers close to completion of the physical monolayer caused by an enhanced elastic scattering rate in the direction perpendicular to the step direction. While multilayers are characterized by weak localization, antilocalization is found for all monolayer structures due to strong spin-orbit coupling, which is effectively switched off around 1.3 ML (1 PML) below 78 K, where one-dimensional transport was seen along the step direction. © 2010 The American Physical Society.DF
Chesapeake Bay Status of Stocks Report 1989-1990
This is the fourth in a series of documents prepared for the Chesapeake Bay Stock Assessment Committee (CBSAC) under the aegis of Status of Stock Knowledge
Electronic transport in one-dimensional Floquet topological insulators via topological and nontopological edge states
Based on probing electronic transport properties we propose an experimental
test for the recently discovered rich topological phase diagram of
one-dimensional Floquet topological insulators with Rashba spin-orbit
interaction [Kennes \emph{et al.}, Phys. Rev. B {\bf 100}, 041103(R) (2019)].
Using the Keldysh-Floquet formalism we compute electronic transport properties
of these nanowires, where we propose to couple the leads in such a way, as to
primarily address electronic states with a large weight at one edge of the
system. By tuning the Fermi energy of the leads to the center of the
topological gap we are able to directly address the topological edge states,
granting experimental access to the topological phase diagram. Surprisingly,
when tuning the lead Fermi energy to special values in the bulk which coincide
with extremal points of the dispersion relation, we find additional peaks of
similar magnitude to those caused by the topological edge states. These peaks
reveal the presence of continua of states centered around aforementioned
extremal points whose wavefunctions are linear combinations of delocalized bulk
states and exponentially localized edge states, where the ratio of edge- to
bulk-state amplitude is maximal at the extremal point of the dispersion. We
discuss the transport properties of these \emph{non-topological edge states},
explain their emergence in terms of an intuitive yet quantitative physical
picture and discuss their relationship with Van Hove singularities in the bulk
of the system. The mechanism giving rise to these states is not specific to the
model we consider here, suggesting that they may be present in a wide class of
one-dimensional systems.Comment: 17 pages, 10 figure
Rational boundary charge in one-dimensional systems with interaction and disorder
We study the boundary charge Q(B) of generic semi-infinite one-dimensional insulators with translational invariance and show that nonlocal symmetries (i.e., including translations) lead to rational quantizations p/q of Q(B). In particular, we find that (up to an unknown integer) the quantization of Q(B) is given in integer units of 1/2 (rho) over bar and 1 2 ((rho) over bar - 1), where (rho) over bar is the average charge per site (which is a rational number for an insulator). This is a direct generalization of the known half-integer quantization of Q(B) for systems with local inversion or local chiral symmetries to any rational value. Quite remarkably, this rational quantization remains valid even in the presence of short-ranged electron-electron interactions as well as static random disorder (breaking translational invariance). This striking stability can be traced back to the fact that local perturbations in insulators induce only local charge redistributions. We establish this result with complementary methods including density matrix renormalization group calculations, bosonization methods, and exact solutions for particular lattice models. Furthermore, for the special case of half-filling (rho) over bar = 1/2, we present explicit results in single-channel and nearest-neighbor hopping models and identify Weyl semimetal physics at gap closing points. Our general framework also allows us to shed new light on the well-known rational quantization of soliton charges at domain walls
Tetranuclear Group 7/8 Mixed-Metal and Open Trinuclear Group 7 Metal Carbonyl Clusters Bearing Bridging 2-mercapto-1-methylimidazole Ligands
The reactivity of group 7 metal dinuclear carbonyl complexes [M2(CO)6(μ-SN2C4H5)2] (1, M = Re; 2, M = Mn) toward group 8 metal trinuclear carbonyl clusters were examined. Reactions of 1 and 2 with [Os3(CO)10(NCMe)2] in refluxing benzene furnished the tetranuclear mixed-metal clusters [Os3Re(CO)13(μ3-SN2C4H5)] (3) and [Os3Mn(CO)13(μ3-SN2C4H5)] (4), respectively. Similar treatment of 1 and 2 with Ru3(CO)12 yielded the ruthenium analogs [Ru3Re(CO)13(μ3-SN2C4H5)] (5), and [Ru3Mn(CO)13(μ3-SN2C4H5)] (6), but in the case of 2 a secondary product [Mn3(CO)10(μ-Cl)(μ3-SN2C4H5)2] (7) was also formed. Compounds 3–6 have a butterfly core of four metal atoms with the M (Mn or Re) at a wingtip of the butterfly and containing a noncrystallographic mirror plane of symmetry. This result provides a potential method for the synthesis of a series of new group 7/8 mixed metal complexes containing a bifunctional heterocyclic ligand. Compound 7 is a unique example of a 54-electron trimanganese complex having bridging 2-mercapto-1-methylimidazolate and chloride ligands. Interestingly, the reaction of 1 with Fe3(CO)12 at 70–75 °C furnished the tri- and dirhenium complexes [Re3(CO)10(μ-H)(μ3-SN2C4H5)2] (8) and [Re2(CO)6(N2C4H5)(μ-SN2C4H5)2] (9), respectively instead of the expected formation of the mixed-metal clusters. The former is an interesting example of a 52-electron trirhenium-hydridic complex containing bridging 2-mercapto-1-methylimidazolate ligand, while the latter can be viewed as a 1-methylimidazole adduct of 1. No mixed Fe–Re complexes were produced in this reaction. The molecular structures of the new compounds 3–5 and 7–9 were established by single-crystal X-ray diffraction analyses and the DFT studies of compounds 5, 7 and 8 are reported
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