86,333 research outputs found
Redistribution of phase fluctuations in a periodically driven cuprate superconductor
We study the thermally fluctuating state of a bi-layer cuprate superconductor
under the periodic action of a staggered field oscillating at optical
frequencies. This analysis distills essential elements of the recently
discovered phenomenon of light enhanced coherence in YBaCuO,
which was achieved by periodically driving infrared active apical oxygen
distortions. The effect of a staggered periodic perturbation is studied using a
Langevin and Fokker-Planck description of driven, coupled Josephson junctions,
which represent two neighboring pairs of layers and their two plasmons. In a
toy model including only two junctions, we demonstrate that the external
driving leads to a suppression of phase fluctuations of the low-energy plasmon,
an effect which is amplified via the resonance of the high energy plasmon. When
extending the modeling to the full layers, we find that this reduction becomes
far more pronounced, with a striking suppression of the low-energy
fluctuations, as visible in the power spectrum. We also find that this effect
acts onto the in-plane fluctuations, which are reduced on long length scales.
All these findings provide a physical framework to describe light control in
cuprates
Probing non-Abelian statistics of Majorana fermions in ultracold atomic superfluid
We propose an experiment to directly probe the non-Abelian statistics of
Majorana fermions by braiding them in an s-wave superfluid of ultracold atoms.
We show different orders of braiding operations give orthogonal output states
that can be distinguished through Raman spectroscopy. Realization of Majorana
bound states in an s-wave superfluid requires strong spin-orbital coupling and
a controllable Zeeman field in the perpendicular direction. We present a simple
laser configuration to generate the artificial spin-orbital coupling and the
required Zeeman field in the dark state subspace.Comment: 4 pages; Add detailed discussion of feasibility of the scheme;add
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Carrier and polarization dynamics in monolayer MoS2
In monolayer MoS2 optical transitions across the direct bandgap are governed
by chiral selection rules, allowing optical valley initialization. In time
resolved photoluminescence (PL) experiments we find that both the polarization
and emission dynamics do not change from 4K to 300K within our time resolution.
We measure a high polarization and show that under pulsed excitation the
emission polarization significantly decreases with increasing laser power. We
find a fast exciton emission decay time on the order of 4ps. The absence of a
clear PL polarization decay within our time resolution suggests that the
initially injected polarization dominates the steady state PL polarization. The
observed decrease of the initial polarization with increasing pump photon
energy hints at a possible ultrafast intervalley relaxation beyond the
experimental ps time resolution. By compensating the temperature induced change
in bandgap energy with the excitation laser energy an emission polarization of
40% is recovered at 300K, close to the maximum emission polarization for this
sample at 4K.Comment: 7 pages, 7 figures including supplementary materia
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