The Effect of the Electron-Phonon Interaction on Giant Magnetoresistance in Magnetic Multilayers

We built electron and phonon free energies and attempted to investigate the effect of the electron-phonon interaction on giant magnetoresistance in magnetic multilayers. Starting from a jellium-like model, we found that the electron-phonon interaction can have an important effect on the spin splitting of electronic energy band. The expression of giant magnetoresistance has been obtained by considering the spin splitting of electronic energy band,indicating that the effect of phonon could not be neglected. Numerical calculations using our approach demonstrate the agreement between experimental and theoretical values.     

Giant Rashba-type spin splitting at polar surfaces of BiTeI

On the basis of relativistic ab initio calculations, we show that both Te- and I-terminated surfaces of the polar layered semiconductor BiTeI hold surface states with a giant Rashba-type spin splitting. The Te-terminated surface state has nearly isotropic free-electron-like dispersion with a positive effective mass, which along with the giant spin splitting makes BiTeI fulfilling the requirements demanded by many semiconductor-spintronics applications. The I-terminated surface state with its negative effective-mass dispersion reproduces nicely the situation with the Rashba-split surface state on surfaces of noble-metal based surface alloys. The crucial advantage of BiTeI as compared with the surface alloys is the location of the I-terminated surface state in a quite wide band gap.     

A study of photoreactions in 48Ti

A high resolution measurement of the ⁴⁸Ti(γ, n) cross section is reported. Evidence for isospin splitting of the giant dipole resonance is found to be consistent with the prediction. In addition the deformation splitting of the GDR is consistent with predictions of the dynamic collective model.     

Quantum theory of spin dynamics of exciton-polaritons in microcavities

We present the quantum theory of momentum and spin relaxation of exciton-polaritons in microcavities. We show that giant longitudinal-transverse splitting of the polaritons mixes their spin states, which results in beats between right- and left-circularly polarized photoluminescence of microcavities, as was recently experimentally observed [Phys. Rev. Lett. 89, 077402 (2002)]]. This effect is strongly sensitive to the bosonic stimulation of polariton scattering.     

The interference between a giant atom and an internal resonator

The Jaynes–Cummings model plays an important role in quantum entanglement and state measurements. Here, we discuss how to realize it in a waveguide-mediated interaction system, which comprises a giant atom and a resonator. We show the vacuum Rabi splitting and discuss how to achieve a unidirectional transport. We extend the Purcell effect in cQED to this waveguide QED system, showing how to control the giant atom decay rate. Our design can further be built experimentally and has application in quantum manipulation.     

Giant spin-orbit bowing in GaAs1-xBix

We report a giant bowing of the spin-orbit splitting energy Delta0 in the dilute GaAs1-xBix alloy for Bi concentrations ranging from 0% to 1.8%. This is the first observation of a large relativistic correction to the host electronic band structure induced by just a few percent of isoelectronic doping in a semiconductor material. It opens up the possibility of tailoring the spin-orbit splitting in semiconductors for spintronic applications.     

溶胶-凝胶法制备Fe-Al_2O_3巨磁旋光薄膜

用溶胶-凝胶法制备了Fe-Al2O3铁磁金属-非磁绝缘体基体薄膜。实验结果表明,当Fe与Al2O3的质量比为1∶1,热处理温度为420℃时,所制备的薄膜具有最大的磁致旋光(Faraday)效应,测得的费尔德(Verdet)常数V=(6.8×104)°/(T.cm)。通过分析,得出了Fe-Al2O3薄膜巨磁Faraday旋光效应主要是由光、磁场与薄膜相互作用产生剧烈塞曼(Zeeman)分裂引起的。对影响薄膜Faraday旋光效应的各种主要因素进行了讨论。     

Ir(111) surface state with giant Rashba splitting persists under graphene in air

We reveal a giant Rashba effect (α(R)≈1.3 eV??) on a surface state of Ir(111) by angle-resolved photoemission and by density functional theory. It is demonstrated that the existence of the surface state, its spin polarization, and the size of its Rashba-type spin-orbit splitting remain unaffected when Ir is covered with graphene. The graphene protection is, in turn, sufficient for the spin-split surface state to survive in ambient atmosphere. We discuss this result along with indications for a topological protection of the surface state.     

Observation of strong-coupling effects in a diluted magnetic semiconductor Ga1-xFexN

The giant Zeeman splitting of free excitons is measured in Ga(1-x)Fe(x)N. Magneto-optical and magnetization data imply the ferromagnetic sign and a reduced magnitude of the effective p-d exchange energy governing the interaction between Fe(3+) ions and holes in GaN, N_{0}beta(app)=+0.5+/-0.2 eV. This finding corroborates the recent suggestion that the strong p-d hybridization specific to nitrides and oxides leads to significant renormalization of the valence band exchange splitting.     

Non axial vibrations in the adiabatic approximation

The adiabatic time-dependent Hartree-Fock method, together with a scaling assumption is used for the calculations of the mass parameters associated with non-axial quadrupole (γ) collective vibrations, and for the study of the splitting of the giant quadrupole resonance in deformed nuclei.     

Two-fluid model description of isovector giant resonances in fast rotating nuclei

Isovector giant resonances of arbitrary multipolarity in fast rotating nuclei are studied by solving the inviscid two-fluid equation of relative motion in a rotating frame of reference. Both Coriolis and centrifugal forces are taken into account. The resulting expressions display in a quite simple way general features of giant multipole resonances of fast rotating nuclei, in addition to a good agreement with other calculations for the giant dipole resonance. Typical values for the resonance energies and their fragmentation due to nuclear deformation and rotation are given. In particular, enormously large resonance splitting should occur in the superdeformed states.     

Optical response of relativistic electrons in the polar BiTeI semiconductor

The transitions between the spin-split bands by spin-orbit interaction are relevant to many novel phenomena such as the resonant dynamical magnetoelectric effect and the spin Hall effect. We perform optical spectroscopy measurements combined with first-principles calculations to study these transitions in the recently discovered giant bulk Rashba spin-splitting system BiTeI. Several novel features are observed in the optical spectra of the material including a sharp edge singularity due to the reduced dimensionality of the joint density of states and a systematic doping dependence of the intraband transitions between the Rashba-split branches. These confirm the bulk nature of the Rashba-type splitting in BiTeI and manifest the relativistic nature of the electron dynamics in a solid.     

Phase-modulated Autler–Townes splitting in a giant-atom system within waveguide QED

The nonlocal emitter-waveguide coupling, which gives birth to the so called giant atom, represents a new paradigm in the field of quantum optics and waveguide QED. We investigate the single-photon scattering in a one-dimensional waveguide on a two-level or three-level giant atom. Thanks to the natural interference induced by the back and forth photon transmitted/reflected between the atom-waveguide coupling points, the photon transmission can be dynamically controlled by the periodic phase modulation via adjusting the size of the giant atom. For the two-level giant-atom setup, we demonstrate the energy shift which is dependent on the atomic size. For the driven three-level giant-atom setup, it is of great interest that, the Autler–Townes splitting is dramatically modulated by the giant atom, in which the width of the transmission valleys (reflection range) is tunable in terms of the atomic size. Our investigation will be beneficial to the photon or phonon control in quantum network based on mesoscopical or even macroscopical quantum nodes involving the giant atom.     

Giant spin splitting through surface alloying

The long-range ordered surface alloy Bi/Ag(111) is found to exhibit a giant spin splitting of its surface electronic structure due to spin-orbit coupling, as is determined by angle-resolved photoelectron spectroscopy. First-principles electronic structure calculations fully confirm the experimental findings. The effect is brought about by a strong in-plane gradient of the crystal potential in the surface layer, in interplay with the structural asymmetry due to the surface-potential barrier. As a result, the spin polarization of the surface states is considerably rotated out of the surface plane.     

Collective excitations in neutron-rich nuclei within the model of a Fermi liquid drop

We discuss a new mechanism of splitting of giant multipole resonances (GMR) in spherical neutron-rich nuclei. This mechanism is associated with the basic properties of an asymmetric drop of nuclear Fermi liquid. In addition to well-known isospin shell-model predictions, our approach can be used to describe the GMR splitting phenomenon in the wide nuclear-mass region A ～ 40–240. For the dipole isovector modes, the splitting energy, the relative strength of resonance peaks, and the contribution to the energy-weighted sum rules are in agreement with experimental data for the integrated cross sections for photonuclear (γ, n) and (γ, p) reactions.     

Magneto-optical study of Mn containing broad gap II–VI quantum well structures and superlattices

Semimagnetic ZnSe/(Zn,Mn)Se single and multiple quantum well structures are studied by luminescence and reflection spectroscopy in a magnetic field up to 7.5 T. Using the strain-induced heavy and light hole splitting of the barrier and well excitons the valence band offset is determined in the framework of a Kronig-Penney model calculation. A unique offset dependence on the manganese concentration and a type conversion due to the giant Zeeman splitting are found.     

Manipulation of nonreciprocal unconventional photon blockade in a cavity-driven system composed of an asymmetrical cavity and two atoms with weak dipole-dipole interaction

We present a work of manipulating collective unconventional photon blockade (UCPB) and nonreciprocal UCPB (NUCPB) in a cavity-driven system composed of an asymmetrical single-mode cavity and two interacting identical two-level atoms (TLAs). When the atoms do not interact directly, the frequency and intensity restrictions of collective UCPB can be specified, and a giant NUCPB exists due to the splitting of optimal atom-cavity coupling strength in proper parameter regime. However, if a weak atom-atom interaction which provides a new and feeble quantum interference pathway to UCPB is taken into account, two restrictions of UCPB are combined complexly, which are rigorous to be matched simultaneously. Due to the push-and-pull effect induced by weak dipole-dipole interaction, the UCPB regime is compressed more or less. NUCPB is improved as a higher contrast is present when the two complex UCPB restrictions are matched, while it is suppressed when the restrictions are mismatched. In general, whether NUCPB is suppressed or promoted depends on its working parameters. Our findings show a prospective access to produce giant quantum nonreciprocity by a couple of weakly interacting atoms.     

Magnetic tuning of exciton–photon resonance in II–VI microcavities

We demonstrate the effectiveness of the giant Zeeman effect in II–VI semimagnetic semiconductors to tune the exciton resonance of quantum wells onto the Fabry–Pérot resonance of a microcavity. A large oscillator strength of 3 × 10¹³cm⁻²per quantum well is deduced from the measured 10.6 meV vacuum Rabi splitting.     

Splitting of the giant dipole resonance in deformed metal clusters

The photoabsorption in small deformed metal clusters is considered. The valence electron spill-out is disregarded. It is shown that in the deformed clusters the giant dipole resonance splits into two separate resonances. This splitting is due to the difference of the oscillator frequencies for the electron motion in the effective field of the deformed clusters. The ratio of the cross-sections in the resonance maxima is obtained. The theoretical results are compared with the experimental data.     

Effects of Arbitrarily Directed Field on Spin Phase Oscillations in Biaxial Molecular Magnets

Quantum phase interference and spin-parity effects are studied in biaxial molecular magnets in a magnetic field at an arbitrarily directed angle.The calculations of the ground-state tunnel splitting are performed on the basis of the instanton technique in the spin-coherent-state path-integral representation,and complemented by exactly numerical diagonalization.Both the Wentzel-Kramers-Brillouin exponent and the pre-exponential factor are obtained for the entire region of the direction of the field.Our results show that the tunnel splitting oscillates with the field for the small field angle,while for the large field angle the oscillation is completely suppressed.This distinct angular dependence,together with the dependence of the tunnel splitting on the field strength,provides an independent test for spin-parity effects in biaxial molexular magnets.The analytical results for the molecular Fes magnet are found to be in good agreement with the numerical simulations,which suggests that even the molecular magnet with total spin S=10 is large enough to be treated as a giant spin system.