910 research outputs found
Ferroelectricity driven by the non-centrosymmetric magnetic ordering in multiferroic TbMn_2O_5: a first-principles study
The ground state structural, electronic and magnetic properties of
multiferroic TbMnO are investigated via first-principles calculations.
We show that the ferroelectricity in TbMnO is driven by the
non-centrosymmetric magnetic ordering, without invoking the spin-orbit coupling
and non-collinear spins. The {\it intrinsic} electric polarization in this
compound is calculated to be 1187 cm, an order of magnitude
larger than previously thought
Conquer the fine structure splitting of excitons in self-assembled InAs/GaAs quantum dots via combined stresses
Eliminating the fine structure splitting (FSS) of excitons in self-assembled
quantum dots (QDs) is essential to the generation of high quality entangled
photon pairs. It has been shown that the FSS has a lower bound under uniaxial
stress. In this letter, we show that the FSS of excitons in a general
self-assembled InGaAs/GaAs QD can be fully suppressed via combined stresses
along the [110] and [010] directions. The result is confirmed by atomic
empirical pseudopotential calculations. For all the QDs we studied, the FSS can
be tuned to be vanishingly small ( 0.1 eV), which is sufficient small
for high quality entangled photon emission.Comment: 4 pages, 3 figure, 1 tabl
- β¦