33 research outputs found
Persistent, controllable circulation of a polariton ring condensate
Persistent circulation is a canonical effect of superfluidity. In previous
experiments, quantized circulation has been observed in polariton condensates,
usually far from equilibrium, but persistent circulation without stirring has
not. We report here the direct observation of quantized circulation of a
polariton condensate in a well-controlled steady state. We can cause the
condensate to circulate in either direction on demand using a short laser
pulse; after this short pulse, the condensate continues to circulate for dozens
to hundreds of rotations around the ring without any further stimulation. Our
theoretical model successfully shows how the pulse causes the circulation
Observation of nonequilibrium motion and equilibration in polariton rings
We present a study of the macroscopic dynamics of a polariton condensate formed by nonresonant optical excitation in a quasi-one-dimensional ring-shaped microcavity. The presence of a gradient in the cavity photon energy creates a macroscopic trap for the polaritons in which a coherent condensate is formed which evolves into a single-mode condensate at late times. With time- and energy-resolved imaging we show the role of interactions in the motion of the condensate as it undergoes equilibration in the ring. These experiments also give a direct measurement of the polariton-polariton interaction strength above the condensation threshold. Our observations are compared to the open-dissipative one-dimensional Gross-Pitaevskii equation which shows excellent qualitative agreement
Modeling Supply Networks and Business Cycles as Unstable Transport Phenomena
Physical concepts developed to describe instabilities in traffic flows can be
generalized in a way that allows one to understand the well-known instability
of supply chains (the so-called ``bullwhip effect''). That is, small variations
in the consumption rate can cause large variations in the production rate of
companies generating the requested product. Interestingly, the resulting
oscillations have characteristic frequencies which are considerably lower than
the variations in the consumption rate. This suggests that instabilities of
supply chains may be the reason for the existence of business cycles. At the
same time, we establish some link to queuing theory and between micro- and
macroeconomics.Comment: For related work see http://www.helbing.or
Dynamics of spin polarization in tilted polariton rings
This is an accepted manuscript of an article published by the American Physical Society in Physical Review B on 22/04/2021, available online: https://doi.org/10.1103/PhysRevB.103.165306
The accepted version of the publication may differ from the final published version.We have observed the effect of pseudomagnetic field originating from the polaritonic analog of spin-orbit coupling [transverse electric and transverse magnetic (TE-TM) splitting] on a polariton condensate in a ring-shaped microcavity. The effect gives rise to a stable four-leaf pattern around the ring as seen from the linear polarization measurements of the condensate photoluminescence. This pattern is found to originate from the interplay of the cavity potential, energy relaxation, and TE-TM splitting in the ring. Our observations are compared to the dissipative one-dimensional spinor Gross-Pitaevskii equation with the TE-TM splitting energy, which shows good qualitative agreement.Published versio