arXiv subjects

Babak H. Seradjeh

Publications and source records attributed to Babak H. Seradjeh.

5 recordsLinked to original sources

arXiv2007

Excitons in QED3 and spin response in a phase-fluctuating d-wave superconductor

We study the particle-hole exciton mode in the QED3 theory of a phase-fluctuating d-wave superconductor in ladder approximation. We derive a Schroedinger-like equation for the exciton bound state and determine the conditions for its existence. We find the dispersion of this mode below the particle-hole continuum and compare our results with the resonance observed in neutron scattering measurements in cuprates.

cond-mat.supr-con↗

arXiv2003

Self-consistent theory of compact QED3 with relativistic fermions

We consider three dimensional quantum electrodynamics (cQED3) with massless relativistic fermions coupled to a compact gauge field using a combined perturbative variational approach. Coupling to matter renders the bare interaction between magnetic monopoles logarithmic at large distances, suggesting the possibility of a confinement-deconfinement transition of the Berezinskii-Kosterlitz-Thouless type in the theory. Our self-consistent calculation suggests, however, that screening effects always destabilise the confined phase, in agreement with the previous renormalisation group study of the same model.

cond-mat.str-el↗

arXiv2003

Permanent confinement in the compact QED3 with fermionic matter

We argue that the compact three dimensional electrodynamics with massless fermions is always confining, in spite of the bare interaction between the magnetic monopoles being rendered logarithmic by fermions. The effect is caused by screening by other dipoles, which transforms the logarithmic back into the Coulomb interaction at large distances. Possible implications for the chiral symmetry breaking for fermions are discussed, and the global phase diagram of the theory is proposed.

cond-mat.str-el↗

arXiv2003

Absence of U(1) spin liquids in two dimensions

Many popular models of fractionalized spin liquids contain neutral fermionic spinon excitations on a Fermi surface, carrying unit charges under a compact U(1) gauge force. We argue that instanton effects generically render such states unstable to confinement in two spatial dimensions, so that all elementary excitations are gauge neutral, and there is no spinon Fermi surface. Similar results are expected to apply to SU(2) spin liquids. However, fractionalized states can appear when the gauge symmetry is broken down to a discrete subgroup by the Higgs mechanism. Our argument generalizes earlier results on confinement in the pure gauge theory, and on the instability of the U(1) staggered flux and algebraic spin liquids with a Dirac spectrum for fermionic spinons.

cond-mat.str-el↗

arXiv2002

Fine structure of chiral symmetry breaking in the $QED_3$ theory of underdoped high-$T_c$ superconductors

We study the effects of the leading irrelevant perturbations on chiral symmetry breaking in the effective $QED_3$ theory of d-wave superconductor-insulator transition in underdoped cuprates. For weak symmetry breaking, the effect of a perturbation on energies of various insulating states can be classified according to its engineering dimension in the maximally symmetric theory. Considering the velocity anisotropy, repulsive interactions, and higher order derivatives we show that the insulating state with the lowest energy is the spin density wave.

cond-mat.supr-con↗