E. V. Gorbar

Supercritical Coulomb center and excitonic instability in graphene

It is well known that there are resonant states with complex energy for the supercritical Coulomb impurity in graphene. We show that opening of a quasiparticle gap decreases the imaginary part of energy,

Gap generation and semimetal-insulator phase transition in graphene

|\text{Im}\text{ }E|

Normal ground state of dense relativistic matter in a magnetic field

, of these states and stabilizes the system. For gapless quasiparticles with strong Coulomb interaction in graphene, we solve the Bethe-Salpeter equation for the electron-hole bound state and show that it has a tachyonic solution for strong enough coupling

Gluonic phase in neutral two-flavor dense QCD

\ensuremath{\alpha}={e}^{2}/\ensuremath{\kappa}\ensuremath{\hbar}{v}_{F}

Radiative corrections to chiral separation effect in QED

leading to instability of the system. In the random-phase approximation, the critical coupling is estimated to be

Neutral Larkin-Ovchinnikov-Fulde-Ferrell State and Chromomagnetic Instability in Two-Flavor Dense QCD

{\ensuremath{\alpha}}_{c}=1.62

Dynamics and phase diagram of the ν = 0 quantum Hall state in bilayer graphene

and is an analog of the critical charge in the Coulomb center problem. We argue that the excitonic instability should be resolved through the formation of an excitonic condensate and gap generation in the quasiparticle spectrum.

Magnetic field driven instability of a charged center in graphene

The gap generation is studied in suspended clean graphene in the continuum model for quasiparticles with the Coulomb interaction. We solve the gap equation with the dynamical polarization function and show that, comparing to the case of the static polarization function, the critical coupling constant lowers to the value \alpha_c=0.92, which is close to that obtained in lattice Monte Carlo simulations. It is argued that additional short-range four-fermion interactions should be included in the continuum model to account for the lattice simulation results. We obtain the critical line in the plane of electromagnetic and four-fermion coupling constants and find a second order phase transition separating zero gap and gapped phases with critical exponents close to those found in lattice calculations.

Collective excitations, instabilities, and the ground state in dense quark matter

The properties of the ground state of relativistic matter in a magnetic field are examined within the framework of a Nambu-Jona-Lasinio model. The main emphasis of this study is the normal ground state, which is realized at sufficiently high temperatures and/or sufficiently large chemical potentials. In contrast to the vacuum state, which is characterized by the magnetic catalysis of chiral symmetry breaking, the normal state is accompanied by the dynamical generation of the chiral shift

Dynamical symmetry breaking on a cylinder in magnetic field

Abstract In the Ginzburg–Landau approach, we describe a new phase in neutral two-flavor quark matter in which gluonic degrees of freedom play a crucial role. We call it a gluonic phase. In this phase gluonic dynamics cure a chromomagnetic instability in the 2SC solution and lead to spontaneous breakdown of the color gauge symmetry, the electromagnetic U ( 1 ) , and the rotational SO ( 3 ) . In other words, the gluonic phase describes an anisotropic medium in which the color and electric superconductivities coexist. Because most of the initial symmetries in this system are spontaneously broken, its dynamics is very rich.