arXiv subjects

S. Mahapatra

Publications and source records attributed to S. Mahapatra.

21 records · Page 2Linked to original sources

arXiv2006

Anomalous in-plane magneto-optical anisotropy of self-assembled quantum dots

We report on a complex nontrivial behavior of the optical anisotropy of quantum dots that is induced by a magnetic field in the plane of the sample. We find that the optical axis either rotates in the opposite direction to that of the magnetic field or remains fixed to a given crystalline direction. A theoretical analysis based on the exciton pseudospin Hamiltonian unambiguously demonstrates that these effects are induced by isotropic and anisotropic contributions to the heavy-hole Zeeman term, respectively. The latter is shown to be compensated by a built-in uniaxial anisotropy in a magnetic field B_c = 0.4 T, resulting in an optical response typical for symmetric quantum dots.

cond-mat.mtrl-sci↗

arXiv2005

Quantum-dot-based optical polarization conversion

We report circular-to-linear and linear-to-circular conversion of optical polarization by semiconductor quantum dots. The polarization conversion occurs under continuous wave excitation in absence of any magnetic field. The effect originates from quantum interference of linearly and circularly polarized photon states, induced by the natural anisotropic shape of the self assembled dots. The behavior can be qualitatively explained in terms of a pseudospin formalism.

cond-mat.mtrl-sci↗

arXiv2002

Intersecting 6-branes from new 7-manifolds with G_2 holonomy

We discuss a new family of metrics of 7-manifolds with G_2 holonomy, which are R^3 bundles over a quaternionic space. The metrics depend on five parameters and have two Abelian isometries. Certain singularities of the G_2 manifolds are related to fixed points of these isometries; there are two combinations of Killing vectors that possess co-dimension four fixed points which yield upon compactification only intersecting D6-branes if one also identifies two parameters. Two of the remaining parameters are quantized and we argue that they are related to the number of D6-branes, which appear in three stacks. We perform explicitly the reduction to the type IIA model.

hep-th↗