Strain induced quantum Hall effect of excitons in graphene

We study the effect of a uniform pseudomagnetic field, induced by a strain in a monolayer and double layer of gapped graphene, acting on excitons. For our analysis it is crucial that the pseudomagnetic field acts on the charges of the constituent particles of the excitons, i.e., the electrons and holes, the same way in contrast to a magnetic field. Moreover, using a circularly polarized laser field, the electrons and the holes can be excited only in one valley of the honeycomb lattice of gapped graphene. This breaks the time-reversal symmetry and provides the possibility to observe the various Quantum Hall phenomena in this pseudomagnetoexciton system. Our study poses a fundamental problem of the quantum Hall effect for composite particles and paves the way for quantum Hall physics of pseudomagnetoexcitons.Comment: 7 pages, 2 figures, Supplementary materials 8 page

Strain-induced quantum Hall phenomena of excitons in graphene

We study direct and indirect pseudomagnetoexcitons, formed by an electron and a hole in the layers of gapped graphene under strain-induced gauge pseudomagnetic field. Since the strain-induced pseudomagnetic field acts on electrons and holes the same way, it occurs that the properties of single pseudomagnetoexcitons, their collective effects and phase diagram are cardinally different from those of magnetoexcitons in a real magnetic field. We have derived wave functions and energy spectrum of direct in a monolayer and indirect pseudomagnetoexcitons in a double layer of gapped graphene. The quantum Hall effect for direct and indirect excitons was predicted in the monolayers and double layers of gapped graphene under strain-induced gauge pseudomagnetic field, correspondingly

Emission cross sections for energetic O+^+(4S,2D,2P^4S,^2D,^2P)-N2_2 collisions

We report measurements of excitation functions for the O$^{+}-$N$_{2}$ process with the incident beam of $1-10$ keV O$^{+}$ in the ground O$^{+}(^{4}S)$ and metastable O$^{+}(^{2}D)$ and O$^{+}(^{2}P)$ states. The measurements are performed with the sufficiently high energy resolution of 0.001 eV, which allows to distinguish the excitation channels. The excitation cross section induced by incident ions in the metastable state O$^{+}(^{2}P)$ is much larger than that for the ground O$^{+}(^{4}S)$. The excitation cross section of N$_{2}^{+}$ ion for (0,0), (0,1) and (1,2) bands system is measured and the ratio of intensities for these bands is established as $10:3:1.$ It is shown that the cross sections for the N$^{+^{\ast }}$ions excitations in the dissociative charge exchange processes increase with the increase of the incident ion energy. The energy dependence of the excitation cross section of the band (0,0) $\lambda=391.4$ nm of the first negative system of the N$_{2}^{+}$ and degree of polarization of radiation in O$^{+}-$N$_{2}$ collision are measured for the first time. An influence of an admixture of the ion metastable state on a degree of polarization is revealed. It is demonstrated that for O$^{+}-$N$_{2}$ collision system the degree of polarization by metastable O$^{+}$($^{2}P$) ions is less compared to those that are in the ground O$^{+}$($^{4}S$) state and the sign of polarization degree of excited molecular ions does not change.Comment: 15 pages, 8 Figure

Baryons in the Field Correlator Method: Effects of the Running Strong Coupling

The ground and P-wave excited states of nnn, nns and ssn baryons are studied in the framework of the Field Correlator Method using the running strong coupling constant in the Coulomb-like part of the three-quark potential. The running coupling is calculated up to two loops in the background perturbation theory. The three-quark problem has been solved using the hyperspherical functions method. The masses of the S- and P-wave baryons are presented. Our approach reproduces and improves the previous results for the baryon masses obtained for the freezing value of the coupling constant. The string correction for the confinement potential of the orbitally excited baryons, which is the leading contribution of the proper inertia of the rotating strings, is estimated.Comment: 13 pages, 1 figure, 5 table

Thomson Scattering of Coherent Diffraction Radiation by an Electron Bunch

The paper considers the process of Thomson scattering of coherent diffraction radiation (CDR) produced by the preceding bunch of the accelerator on one of the following bunches. It is shown that the yield of scattered hard photons is proportional to N$_e^3$, where N$_e$ is the number of electrons per bunch. A geometry is chosen for the CDR generation and an expression is obtained for the scattered photon spectrum with regard to the geometry used, that depends in an explicit form on the bunch size. A technique is proposed for measuring the bunch length using scattered radiation characteristics.Comment: 14 pages, LATEX, 6 ps.gz figures, submitted to Phys.Rev.

Experimental investigation of high-energy photon splitting in atomic fields

The new data analysis of the experiment, where the photon splitting in the atomic fields has been observed for the first time, is presented. This experiment was performed at the tagged photon beam of the ROKK-1M facility at the VEPP-4M collider. In the energy region of 120-450 MeV, the statistics of $1.6\cdot 10^9$ photons incident on the BGO target was collected. About 400 candidates to the photon splitting events were reconstructed. Within the attained experimental accuracy, the experimental results are consistent with the cross section calculated exactly in an atomic field. The predictions obtained in the Born approximation significantly differ from the experimental results.Comment: 11 pages, 6 figures, LaTe