287 research outputs found
Casimir effect for lattice fermions
We propose a definition of the Casimir energy for free lattice fermions. From
this definition, we study the Casimir effects for the massless or massive naive
fermion, Wilson fermion, and (M\"obius) domain-wall fermion in
dimensional spacetime with the spatial periodic or antiperiodic boundary
condition. For the naive fermion, we find an oscillatory behavior of the
Casimir energy, which is caused by the difference between odd and even lattice
sizes. For the Wilson fermion, in the small lattice size of , the
Casimir energy agrees very well with that of the continuum theory, which
suggests that we can control the discretization artifacts for the Casimir
effect measured in lattice simulations. We also investigate the dependence on
the parameters tunable in M\"obius domain-wall fermions. Our findings will be
observed both in condensed matter systems and in lattice simulations with a
small size.Comment: 8 pages, 5 figures; published versio
Casimir effect in axion electrodynamics with lattice regularizations
The Casimir effect is induced by the interplay between photon fields and
boundary conditions, and in particular, photon fields modified in axion
electrodynamics may lead to the sign-flipping of the Casimir energy. We propose
a theoretical approach to derive the Casimir effect in axion electrodynamics.
This approach is based on a lattice regularization and enables us to discuss
the dependence on the lattice spacing for the Casimir energy. With this
approach, the sign-flipping behavior of the Casimir energy is correctly
reproduced. By taking the continuum limit of physical quantity calculated on
the lattice, we can obtain the results consistent with the continuum theory.
This approach can also be applied to the Casimir effect at nonzero temperature.Comment: 11 pages, 9 figure
Lattice-fermionic Casimir effect and topological insulators
The Casimir effect arises from the zero-point energy of particles in momentum
space deformed by the existence of two parallel plates. For degrees of freedom
on the lattice, its energy-momentum dispersion is determined so as to keep a
periodicity within the Brillouin zone, so that its Casimir effect is modified.
We study the properties of Casimir effect for lattice fermions, such as the
naive fermion, Wilson fermion, and overlap fermion based on the M\"obius
domain-wall fermion formulation, in the -, -, and -dimensional
space-time with the periodic or antiperiodic boundary condition. An oscillatory
behavior of Casimir energy between odd and even lattice size is induced by the
contribution of ultraviolet-momentum (doubler) modes, which realizes in the
naive fermion, Wilson fermion in a negative mass, and overlap fermions with a
large domain-wall height. Our findings can be experimentally observed in
condensed matter systems such as topological insulators and also numerically
measured in lattice simulations.Comment: 27 pages, 9 figures; published versio
Stabilization of a honeycomb lattice of IrO octahedra in superlattices with ilmenite-type MnTiO
In the quest for quantum spin liquids, thin films are expected to open the
way for the control of intricate magnetic interactions in actual materials by
exploiting epitaxial strain and two-dimensionality. However, materials
compatible with conventional thin-film growth methods have largely remained
undeveloped. As a promising candidate towards the materialization of quantum
spin liquids in thin films, we here present a robust ilmenite-type oxide with a
honeycomb lattice of edge-sharing IrO octahedra artificially stabilized by
superlattice formation with an ilmenite-type antiferromagnetic oxide MnTiO.
The stabilized sub-unit-cell-thick Mn-Ir-O layer is isostructural to MnTiO,
having the atomic arrangement corresponding to ilmenite-type MnTiO not
discovered yet. By spin Hall magnetoresistance measurements, we found that
antiferromagnetic ordering in the ilmenite Mn sublattice is suppressed by
modified magnetic interactions in the MnO planes via the IrO planes.
These findings lay the foundation for the creation of two-dimensional Kitaev
candidate materials, accelerating the discovery of exotic physics and
applications specific to quantum spin liquids
Development of teaching materials for improving communication skills in Corona disaster
コロナ禍によって大学のアクティブラーニング型授業は大きな方向転換を余儀なくされた。学生のコミュニケーション力を目指して開講していた岡山大学の教養科目の授業でも、従来の双方向型コミュニケーション実践を軸とした授業内容を大幅に改める必要に迫られた。そこで、コミュニケーション力を下支えするメタ認知力の育成を目的とした、日々の生活のリフレクションを通した考察を行うための教材を開発した。その後、教材を活用した授業を実践し、授業の前後、学生へのアンケート調査を行った結果、本教材を用いた授業を行ったことにより、学生のメタ認知力が向上したことが明らかになった
Synthesis and electrochemistry of dimanganese(II) complexes of phenol-based dinucleating ligands with four methoxyethyl chelating arms
Dimanganese(II) complexes [Mn2(bonp)(PhCO2)2]PF6 (1) and [Mn2(bocp)(PhCO2)2]PF6 (2) were synthesized with p-nitro- and p-chloro-substituted phenol-based dinucleating ligands bonp- [2,6-bis[bis(2-methoxyethyl)aminomethyl]-4-nitrophenolate anion] and bocp- [4-chloro-2,6-bis[bis(2-methoxyethyl)aminomethyl]phenolate anion], respectively, with the aim of controlling the redox potentials of the dimanganese center by changing the p-substituents in the dinucleating ligands. Cyclic voltammograms of 1 and 2 showed quasi-reversible oxidation processes, assigned to MnIIMnII/MnIIMnIII, at 1.17 and 1.00 V vs. Ag/AgCl, respectively. Compared to the previous p-methyl complex [Mn2(bomp)(PhCO2)2]PF6 (3) [bomp–: 2,6-bis[bis(2-methoxyethyl)aminomethyl]-4-methylphenolate anion] (0.96 V vs. Ag/AgCl), the order of the potentials was 1(-NO2) > 2(-Cl) > 3(-CH3). Thus, the redox potentials of the dimanganese centers were controlled by the p-substituents in the dinucleating ligands
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