Phase-Controlled Bistability of a Dark Soliton Train in a Polariton Fluid

Abstract

We use a one-dimensional polariton fluid in a semiconductor microcavity to explore the rich nonlinear dynamics of counter-propagating interacting Bose fluids. The intrinsically driven-dissipative nature of the polariton fluid allows to use resonant pumping to impose a phase twist across the fluid. When the polariton-polariton interaction energy becomes comparable to the kinetic energy, linear interference fringes transform into a train of solitons. A novel type of bistable behavior controlled by the phase twist across the fluid is experimentally evidenced.Dark solitons are among the fundamental nonlinear collective excitations of one-dimensional (1D) quantum degenerate fluids with positive mass and repulsive interactions. They are characterized by a dip in a uniform background density and a jump in the macroscopic phase across it. The shape and size of the dip is given by the interplay of mass and nonlinearity. Because of the universality of the mechanisms necessary to their formation, dark solitons have been observed in a wide variety of systems ranging from Bose-Einstein condensates of cold atoms [1][2][3], optical fibers [4], to thin magnetic films [5]. Interestingly, dark solitons have also been observed in nonlinear open-dissipative systems, in particular, in semiconductor microcavities [6][7][8][9] and are attracting great interest in view of photonic applications [10].Semiconductor microcavities have recently appeared as an excellent platform to study the nonlinear dynamics of interacting Bose fluids in a photonic context [11]. Their elementary excitations are exciton-polaritons, bosonic quasiparticles arising from the strong coupling between quantum well excitons and photons confined in the microcavity. While their excitonic component provides significant repulsive interactions, the fast escape of photons out of the microcavity makes polaritons an intrinsically open-dissipative system, requiring continuous wave pumping to achieve a steady state. A number of quantum fluid effects have been studied in semiconductor microcavities, including superfluidity [12], diffusive Goldstone modes [13], Bogoliubov excitation spectrum [14], solitary bright waves [15,16], and the hydrodynamic nucleation of quantized vortices [17,18] and dark solitons [7,8].In addition to the possibility of in-situ and timeresolved imaging of the fluid dynamics, a remarkable feature of driven-dissipative systems is that a resonant drive allows setting the local phase of the wavefunction [11]. It is then possible to externally manipulate the boundary conditions and impose a controlled phase pattern across a polariton fluid. This was first explored in a two-dimensional polariton condensate in which a spatial vortex phase profile was imposed on the polariton field, resulting in persistent currents with high orbital momentum [19]. This technique opens up a new world for the exploration of the elementary excitations of polariton quantum fluids. In particular, it has been proposed that by imposing a phase twist across the fluid via the external...

Beyond superfluidity in non-equilibrium Bose–Einstein condensates

“…This reduced drag has been explained by the finite lifetime of Bogoliubov modes due to drain present in this open system [30]. In addition it has been realised that elementary excitations known from equilibrium condensates exist too-dark solitons are feasible in 1d [32,33] or quantised vortices in 2d non-equilibrium condensates [34,35] above a specific critical velocity or even spontaneously due to purely non-equilibrium dynamics [36]. The mathematical extension of the governing partial differential equation for open BEC in those scenarios implies intrinsic adaptions of the excitations' mathematical form [32,37] (see e.g.…”

Dynamics of defect-induced dark solitons in an exciton-polariton condensate

“…The use of GPE makes it possible to describe fundamental properties of dark and bright solitons in a polariton condensate, such as their dynamics, stability, and continous emission [27][28][29][30][31][32][33][34]. Successful creation of nonlinear excitations and their manipulation gave rise to a new concept of information processing based on vortices and soliton dynamics [35][36][37]. It is important to note that using dark solitons or quantized vortices for information processing devices requires a precise description of nonlinear dynamics, which is the aim of our work.…”

Coherent merging of counterpropagating exciton-polariton superfluids

“…Moreover, polaritonic systems are easily controllable by optical techniques and, due to their finite lifetimes, are ideal systems for studying outof-equilibrium phenomena [8,9]. In analogy with the atomic case [10,11], condensation [12] and the superfluid behavior of polaritonic quantum fluids [13] have been of great theoretical interest [14-16] and have been experimentally confirmed [17][18][19].Recently, multi-pumps settings were explored to form polariton condensates by off-resonant excitation of spatially distinct areas [20,21], and to study the collision of strongly interacting fluids in a resonant excitation regime [22][23][24]. This allows for example the condensa-tion of polaritons in a pump-free zone surrounded by the excitation spots [20] or the formation of nonlinear collective excitations (dark solitons and vortices) with resonant driving [22][23][24].…”

“…In analogy with the atomic case [10,11], condensation [12] and the superfluid behavior of polaritonic quantum fluids [13] have been of great theoretical interest [14-16] and have been experimentally confirmed [17][18][19].Recently, multi-pumps settings were explored to form polariton condensates by off-resonant excitation of spatially distinct areas [20,21], and to study the collision of strongly interacting fluids in a resonant excitation regime [22][23][24]. This allows for example the condensa-tion of polaritons in a pump-free zone surrounded by the excitation spots [20] or the formation of nonlinear collective excitations (dark solitons and vortices) with resonant driving [22][23][24]. Interestingly, it is found that the density of such excitations diminishes as the interactions increase [24] and that the strong interactions regime can lead to the merging of vortex-antivortex (V-AV) pairs [25], paving the way to a perfect merging of distinct Bose gases, as reported here.In the present work, we focus on achieving the complete vanishing of all interference and the annihilation of all phase singularities inside a two-dimensional, square geometry four-pumps system.…”