Propagation of polariton fluidsPropagation of polariton fluidsand its controland its control

Tomas Ostatnický, Alexey V. Kavokin

Motivation

Spintronics – information stored in spinNeed of spin transport and processing

Microcavity polaritons: half-photon, half-excitoncombination of both, may carry spin and interactpromising for spin-optronic circuits

Electronics Photonics

Diffusive Ballistic Propagation

Resistivity Losses

~ 0 Interactions

~ 10 m Spin transport

Theoretical approach: fluids

Assume local thermal equilibrium

Thermodynamical description

Parameters: density, current, entropy

Propagation controlled by static potential and chemical potential

Towards superfluidity: multiple fluids

Superfluidity in He II explained by L. Landau in terms of two-fluid model

Coexistence of two interacting fluids: a normal fraction anda superfluid fraction

Mutual interactions much weaker than interactions within fluid fractions

Multiple fluids & polaritons (1)

Helium atoms

Infinite lifetimeConstant density

One normal fraction

Polaritons

Finite lifetimeVariable density

Multiple normal fractionsLA-phonon assisted transition rate

(depending on QW width)

Multiple fluids & polaritons (2)

Concept of Landau adapted for polaritons

Conservation laws +Navier-Stokes equation

+ friction + lifetime

4 equations for and S: the last equation is the equation of stateDetermines potential, pressure and temperatureBoth superfluid (coherent) and normal fractions present in model

nsns vv ,,,

Superfluidity of polaritons

Expansion of normal component Shock waves in superfluid

Polariton circuits (1)

1D quantum wire with single parabolic bandOne or Two “sources” on sidesVariable potential barrier by electric field

Polariton circuits (2)

Steady-state chemical potential – comparison with electronsLifetime taken to be infiniteSource on the left, 0 on the right

Polariton circuits (3)

Equilibrium established after t = lifetimeHere = 1 ns

Polariton circuits (4)

Variable friction Variable lifetime

Polariton circuits (5)

Two normal fluids from two sources with and without mutual friction

Polariton circuits (6)

Control by locally applied electric field in normal direction

Conclusions

Modelling of polariton fluid propagationSuperfluidity and coexistence of both fractions includedResults of simulations reveal behaviour of polaritons similar to

electronics but with some peculiaritiesPossibility of construction of circuits with propagating polaritonsPossibility of dynamical control by external electric field

Electronics Photonics Polaritons

Diffusive Ballistic Ballistic Propagation

Resistivity Lifetime Losses

~ 0 Interactions

~ 10 m Spin transport