Magnetization steps in Zn_(1-x)Mn_xO: Four largest exchange constants and single-ion anisotropy

Magnetization steps (MST's) from Mn pairs in several single crystals of Zn_(1-x)Mn_xO (0.0056<=x<=0.030, and in one powder (x=0.029), were observed. The largest two exchange constants, J1/kB=-18.2+/-0.5K and J1'/kB=-24.3+/-0.6K, were obtained from large peaks in the differential susceptibility, dM/dH, measured in pulsed magnetic fields, H, up to 500 kOe. These two largest J's are associated with the two inequivalent classes of nearest neighbors (NN's) in the wurtzite structure. The 29% difference between J1 and J1' is substantially larger than 13% in CdS:Mn, and 15% in CdSe:Mn. The pulsed-field data also indicate that, despite the direct contact between the samples and a superfluid-helium bath, substantial departures from thermal equilibrium occurred during the 7.4 ms pulse. The third- and fourth-largest J's were determined from the magnetization M at 20 mK, measured in dc magnetic fields H up to 90 kOe. Both field orientations H||c and H||[10-10] were studied. (The [10-10] direction is perpendicular to the c-axis, [0001].) By definition, neighbors which are not NN's are distant neighbors (DN's). The largest DN exchange constant (third-largest overall), has the value J/kB=-0.543+/-0.005K, and is associated with the DN at r=c. Because this is not the closest DN, this result implies that the J's do not decrease monotonically with the distance r. The second-largest DN exchange constant (fourth-largest overall), has the value J/kB=-0.080 K. It is associated with one of the two classes of neighbors that have a coordination number z=12, but the evidence is insufficient for a definite unique choice. The dependence of M on the direction of H gives D/kB=-0.039+/-0.008K, in fair agreement with -0.031 K from earlier EPR work.Comment: 12 pages, 10 figures. Submitted to PR

Zitterbewegung of exciton-polaritons

Macroscopic wave packets of spin-polarized exciton-polaritons in two-dimensional microcavities experience the zitterbewegung, the effect manifested by the appearance of the oscillatory motion of polaritons in the direction normal to the initial propagation direction. The oscillating trajectories of exciton-polaritons are adjustable by the control parameters: the splitting of the longitudinal and transverse exciton-polariton modes, the wave vector, and the width of the resonant cw pump. Our theoretical analysis supported by the numerical calculations allowed us to optimize values of the control parameters suitable for a direct experimental observation of the zitterbewegung effect. © 2018 American Physical Societ

Suppression of superfluidity of exciton-polaritons by magnetic field

We show that the properties of exciton-polariton condensate in a semiconductor microcavity are strongly sensitive to the external magnetic field normal to the cavity plane. In particular, the superfluidity is suppressed at a critical magnetic field Bc proportional to the polariton concentration. For B&lt;Bc the Zeeman splitting of polaritons is exactly compensated by polariton–polariton interactions in the elliptically polarized condensate. Above the critical point, the spin degeneracy is lifted and the superfluidity reappears again on the circularly polarized lower polariton branch.<br/

Zitterbewegung of exciton-polaritons

Macroscopic wave packets of spin-polarized exciton-polaritons in two-dimensional microcavities experience the zitterbewegung, the effect manifested by the appearance of the oscillatory motion of polaritons in the direction normal to the initial propagation direction. The oscillating trajectories of exciton-polaritons are adjustable by the control parameters: the splitting of the longitudinal and transverse exciton-polariton modes, the wave vector, and the width of the resonant cw pump. Our theoretical analysis supported by the numerical calculations allowed us to optimize values of the control parameters suitable for a direct experimental observation of the zitterbewegung effect

Polariton polarization-sensitive phenomena in planar semiconductor microcavities

10.1088/0268-1242/25/1/013001Semiconductor Science and Technology251-SSTE

Polariton laser: thermodynamics and quantum kinetic theory

Cavity exciton–polaritons are considered to be two-dimensional weakly interacting true bosons. We analyse their thermodynamic properties and show that they can exhibit local condensation or Kosterlitz–Thouless phase transition towards superfluidity, so that polariton lasing can be achieved. The dynamical evolution of the condensate in a non-resonantly pumped cavity is described by a quantum kinetic formalism. The distribution function of polaritons is described by a semi-classical Boltzmann equation. A master equation for the ground-state density matrix is derived in the framework of the Born–Markov approximation. The dynamics of the ground-state population and its coherence are deduced

Engineering spatial coherence in lattices of polariton condensates

Artificial lattices of coherently coupled macroscopic states are at the heart of applications ranging from solving hard combinatorial optimisation problems to simulating complex many-body physical systems. The size and complexity of the problems scales with the extent of coherence across the lattice. Although the fundamental limit of spatial coherence depends on the nature of the couplings and lattice parameters, it is usually engineering constrains that define the size of the system. Here, we engineer polariton condensate lattices with active control on the spatial arrangement and condensate density that result in near-diffraction limited emission, and spatial coherence that exceeds by nearly two orders of magnitude the size of each individual condensate. We utilise these advancements to unravel the dependence of spatial correlations between polariton condensates on the lattice geometry

Data for Engineering spatial coherence in lattices of polariton condensates

Experimental data and numerical simulation results used to create the figures in the paper J. D. T&ouml;pfer, I. Chatzopoulos, H. Sigurdsson, T. Cookson, Y. G. Rubo, and P. G. Lagoudakis (2020), Engineering spatial coherence in lattices of polariton condensates, Optica.</span

The long-run diversification attributes of commercial property

Bosonic cascades formed by lattices of equidistant energy levels sustaining radiative transitions between nearest layers represent a unique system to study correlated optical phenomena. We show how the light emitted by condensates in the visible range introduces a new regime of emission for cascade systems. Namely, the quantum statistics of bosonic cascades exhibits superbunching plateaus. This demonstrates further potentialities of bosonic cascade lasers for the engineering of correlated properties of light useful for imaging applications

Nontrivial phase coupling in polariton multiplets

Data supporting the publication Ohadi, H.; Gregory, R. L.; Freegarde, T.; Rubo, Y. G.; Kavokin, A. V.; Berloff, N. G.; Lagoudakis, P. G., Nontrivial Phase Coupling in Polariton Multiplets. Physical Review X 2016, 6 (3), DOI: 10.1103/PhysRevX.6.031032</span