28 research outputs found
Nanoskyrmion engineering with -electron materials: Sn monolayer on SiC(0001) surface
Materials with -magnetism demonstrate strongly nonlocal Coulomb
interactions, which opens a way to probe correlations in the regimes not
achievable in transition metal compounds. By the example of Sn monolayer on
SiC(0001) surface, we show that such systems exhibit unusual but intriguing
magnetic properties at the nanoscale. Physically, this is attributed to the
presence of a significant ferromagnetic coupling, the so-called direct
exchange, which fully compensates ubiquitous antiferromagnetic interactions of
the superexchange origin. Having a nonlocal nature, the direct exchange was
previously ignored because it cannot be captured within the conventional
density functional methods and significantly challenges ground state models
earlier proposed for Sn/SiC(0001). Furthermore, heavy adatoms induce strong
spin-orbit coupling, which leads to a highly anisotropic form of the spin
Hamiltonian, in which the Dzyaloshinskii-Moriya interaction is dominant. The
latter is suggested to be responsible for the formation of a nanoskyrmion state
at realistic magnetic fields and temperatures.Comment: 4 pages, supplemental materia
Quantum correlations in spin models
Bell nonlocality, entanglement and nonclassical correlations are different
aspects of quantum correlations for a given state. There are many methods to
measure nonclassical correlations. In this paper, nonclassical correlations in
two-qubit spin models are measured by use of measurement-induced disturbance
(MID) [Phys. Rev. A, 77, 022301 (2008)] and geometric measure of quantum
discord (GQD) [Phys. Rev. Lett. 105, 190502 (2010)]. Their dependencies on
external magnetic field, spin-spin coupling, and Dzyaloshinski-Moriya (DM)
interaction are presented in detail. We also compare Bell nonlocality,
entanglement measured by concurrence, MID and GQD and illustrate their
different characteristics.Comment: 1 text and 5 eps figures, accepted by Annals of Physic
Factorization and Criticality in the Anisotropic XY Chain via Correlations
In this review, we discuss the zero and finite temperature behavior of
various bipartite quantum and total correlation measures, the skew
information-based quantum coherence, and the local quantum uncertainty in the
thermal ground state of the one-dimensional anisotropic XY model in transverse
magnetic field. We compare the ability of considered measures to correctly
detect or estimate the quantum critical point and the non-trivial factorization
point possessed by the spin chain.Comment: 29 pages, 8 figures. A review paper accepted for publication in the
special issue Entanglement Entropy in the journal Entrop
Prisoners’ dilemma in a spatially separated system based on spin–photon interactions
This research was funded by the Personal Research Fund of Tokyo International University.Having access to ideal quantum mechanical resources, the prisoners’ dilemma can be ceased. Here, we propose a distributed quantum circuit to allow spatially separated prisoners to play the prisoners’ dilemma game. Decomposing the circuit into controlled-Z and single-qubit gates only, we design a corresponding spin–photon-interaction-based physical setup within the reach of current technology. In our setup, spins are considered to be the players’ logical qubits, which can be realized via nitrogen-vacancy centers in diamond or quantum dots coupled to optical cavities, and the game is played via a flying photon realizing logic operations by interacting with the spatially separated optical cavities to which the spin qubits are coupled. We also analyze the effect of the imperfect realization of two-qubit gates on the game, and discuss the revival of the dilemma and the emergence of new Nash equilibria.Publisher's VersionQ3WOS:00085696110000
Improving the bidirectional steerability between two accelerated partners via filtering process
The bidirectional steering between two accelerated partners sharing initially
different classes of entangled states is discussed. Due to the decoherence, the
steerability and its degree decrease either as the acceleration increases or
the partners share initially a small amount of quantum correlations. The
possibility of increasing the steerability is investigated by applying the
filtering process. Our results show that by increasing the filtering strength,
one can improve the upper bounds of the steerability and the range of
acceleration at which the steerability is possible. Steering large coherent
states is much better than steering less coherent ones
New Perspectives for Rashba Spin-Orbit Coupling
In 1984, Bychkov and Rashba introduced a simple form of spin-orbit coupling
to explain certain peculiarities in the electron spin resonance of
two-dimensional semiconductors. Over the past thirty years, similar ideas have
been leading to a vast number of predictions, discoveries, and innovative
concepts far beyond semiconductors. The past decade has been particularly
creative with the realizations of means to manipulate spin orientation by
moving electrons in space, controlling electron trajectories using spin as a
steering wheel, and with the discovery of new topological classes of materials.
These developments reinvigorated the interest of physicists and materials
scientists in the development of inversion asymmetric structures ranging from
layered graphene-like materials to cold atoms. This review presents the most
remarkable recent and ongoing realizations of Rashba physics in condensed
matter and beyond.Comment: 56 pages, 7 figures, 3 boxes; Accepted for publication in Nature
Materials. The present version is the original one, before passing by the
referee
Non-Hermitian Topological Magnonics
Dissipation in mechanics, optics, acoustics, and electronic circuits is
nowadays recognized to be not always detrimental but can be exploited to
achieve non-Hermitian topological phases or properties with functionalities for
potential device applications. As elementary excitations of ordered magnetic
moments that exist in various magnetic materials, magnons are the information
carriers in magnonic devices with low-energy consumption for reprogrammable
logic, non-reciprocal communication, and non-volatile memory functionalities.
Non-Hermitian topological magnonics deals with the engineering of dissipation
and/or gain for non-Hermitian topological phases or properties in magnets that
are not achievable in the conventional Hermitian scenario, with associated
functionalities cross-fertilized with their electronic, acoustic, optic, and
mechanic counterparts, such as giant enhancement of magnonic frequency combs,
magnon amplification, (quantum) sensing of the magnetic field with
unprecedented sensitivity, magnon accumulation, and perfect absorption of
microwaves. In this review article, we address the unified approach in
constructing magnonic non-Hermitian Hamiltonian, introduce the basic
non-Hermitian topological physics, and provide a comprehensive overview of the
recent theoretical and experimental progress towards achieving distinct
non-Hermitian topological phases or properties in magnonic devices, including
exceptional points, exceptional nodal phases, non-Hermitian magnonic SSH model,
and non-Hermitian skin effect. We emphasize the non-Hermitian Hamiltonian
approach based on the Lindbladian or self-energy of the magnonic subsystem but
address the physics beyond it as well, such as the crucial quantum jump effect
in the quantum regime and non-Markovian dynamics. We provide a perspective for
future opportunities and challenges before concluding this article.Comment: 101 pages, 35 figure