Search results for "BAND"
showing 10 items of 2610 documents
Evolution from γ -soft to stable triaxiality in Nd136 as a prerequisite of chirality
2018
The level structure of Nd136 has been investigated using the Mo100(Ar40,4n) reaction and the JUROGAM II+RITU+GREAT setup. The level scheme has been extended significantly. Many new bands have been identified both at low and high spin, among which are five nearly degenerate bands interpreted as chiral partners. Excitation energies, spins, and parities of the previously known bands are revised and firmly established, and some previously known bands have been revised. Configurations are assigned to the observed bands based on cranked Nilsson-Strutinsky calculations. The band structure of Nd136 is now clarified and the various types of single-particle and collective excitations are well underst…
Antiferromagnetic Topological Insulator with Nonsymmorphic Protection in Two Dimensions
2019
The recent demonstration of topological states in antiferromagnets (AFMs) provides an exciting platform for exploring prominent physical phenomena and applications of antiferromagnetic spintronics. A famous example is the AFM topological insulator (TI) state, which, however, was still not observed in two dimensions. Using a tight-binding model and first-principles calculations, we show that, in contrast to previously observed AFM topological insulators in three dimensions, an AFM TI can emerge in two dimensions as a result of a nonsymmorphic symmetry that combines the twofold rotation symmetry and half-lattice translation. Based on the spin Chern number, Wannier charge centers, and gapless …
Magnetism-mediated transition between crystalline and higher-order topological phases in NpSb
2021
Merging the fields of topology and magnetism expands the scope of fundamental quantum phenomena with novel functionalities for topological spintronics enormously. Here, we theoretically demonstrate that ferromagnetism provides an efficient means to achieve a topological switching between crystalline and higher-order topological insulator phases in two dimensions. Using a tight-binding model and first-principles calculations, we identify layered NpSb as a long-awaited two-dimensional topological crystalline insulator with intrinsic ferromagnetic order with a band gap which is as large as 220 meV. We show that when ${\mathcal{M}}_{z}$ symmetry is preserved for the out of plane magnetization o…
Finite Frequency Vibration Control for Polytopic Active Suspensions via Dynamic Output Feedback
2013
This paper presents a disturbance attenuation strategy for active suspension systems with frequency band constraints, where dynamic output feedback control is employed in consideration that not all the state variables can be measured on-line. In view of the fact that human are sensitive to the virbation between 4–8 Hz in vertical direction, the control based on generalized Kalman-Yakubovich-Popov (KYP) lemma is developed in this specific frequency, in order to achieve the targeted disturbance attenuation. Moreover, practical constraints required in active suspension design are guaranteed in the whole time domain. At the end of the paper, the outstanding performance of the system using finit…
Structure of rotational bands in 253No
2009
In-beam gamma-ray and conversion electron spectroscopic studies have been performed on the 253 No nucleus. A strongly coupled rotational band has been identified and the improved statistics allows an assignment of the band structure as built on the $\ensuremath 9/2^-[734]_{\nu}$ ground state. The results agree with previously known transition energies but disagree with the tentative structural assignments made in earlier work.
Generation of robust entangled states in a non-hermitian periodically driven two-band Bose-Hubbard system
2016
A many-body Wannier-Stark system coupled to an effective reservoir is studied within a non-Hermitian approach in the presence of a periodic driving. We show how the interplay of dissipation and driving dynamically induces a subspace of states which are very robust against dissipation. We numerically probe the structure of these asymptotic states and their robustness to imperfections in the initial-state preparation and to the size of the system. Moreover, the asymptotic states are found to be strongly entangled making them interesting for further applications.
Pressure tuning of light-induced superconductivity in K3C60
2017
Optical excitation at terahertz frequencies has emerged as an effective means to manipulate complex solids dynamically. In the molecular solid K3C60, coherent excitation of intramolecular vibrations was shown to transform the high temperature metal into a non-equilibrium state with the optical conductivity of a superconductor. Here we tune this effect with hydrostatic pressure, and we find it to disappear around 0.3 GPa. Reduction with pressure underscores the similarity with the equilibrium superconducting phase of K3C60, in which a larger electronic bandwidth is detrimental for pairing. Crucially, our observation excludes alternative interpretations based on a high-mobility metallic phase…
Phase diagram of dirty two-band superconductors and observability of impurity-induced $s+is$ state
2016
We investigate the phase diagram of dirty two-band superconductors. This paper primarily focuses on the properties and observability of the time-reversal symmetry-breaking $s+is$ superconducting states, which can be generated in two-band superconductors by interband impurity scattering. We show that such states can appear in two distinct ways. First, according to a previously discussed scenario, the $s+is$ state can form as an intermediate phase at the impurity-driven crossover between $s_{\pm}$ and $s_{++}$ states. We show that there is a second scenario where domains of the $s+is$ state exists in the form of an isolated dome inside the $s_{\pm}$ domain, completely detached from the transi…
Phonons in an inhomogeneous continuum: Vibrations of an embedded nanoparticle
2004
The spectrum of acoustic vibrational modes of an inhomogeneous elastic continuum are analyzed with application to a spherical nanoparticle embedded in an infinite glass block. The relationship of these modes to the discrete vibrational spectrum of a free sphere is studied. The vibrational modes of a sphere with a fixed surface are relevant in some situations. Comparisons are also made to calculations of mode frequency and damping based on complex valued frequency.
Review on up/down conversion materials for solar cell application
2012
The present paper reviews the methods of photon up- and down conversion strategies for improving the efficiency of solar cells. Photons with a lower energy than the band gap will be lost in a normal solar cell. The principle of the up conversion technique is that two or more photons are converted into a photon with energy higher than the band gap energy. High energy photons will lose the energy above the band gap energy limit. Down conversion is a process where a high energy photon is converted into several lower energy photons with energies above the band gap. A description is given of the most common methods and materials for these conversions resulting in higher solar cell efficiencies.