Drag force of an exciton-polariton condensate under nonresonant pumping

Interaction between an impurity and nonlinear excitations in a polariton condensate

“…The motion of an impurity through a dynamical medium that consists of field excitations is a fundamental physical problem. Since Landau's seminal paper [1,2] on the electron dressed by phonons, this problem has been at the heart of numerous important phenomena, such as the Kondo [3] and Cherenkov [4][5][6] effects, as well as the introduction of the concept of polaron [7] and the Landau criterion [8][9][10][11][12] for the sound speed of a superfluid. At the moment, there are great interests and efforts in studying a mobile impurity in a quantum medium in diverse areas [13][14][15][16][17][18][19].…”

“…Central to understanding the dynamics of an impurity in an interacting quantum many-body medium is to include the entanglement between the impurity and the surrounding excitations in a wide range of energy scales by choosing the impurity's effective mass to be finite, rather than infinite [8][9][10][11][12]. These excitations can be classified as linear excitations and nonlinear excitations.…”

“…The linear excitations are provided by the diffusive Goldstone modes [20][21][22][23], with observable ghost branches of Bogoliubov excitations [24]. This have already prompted questions and studies on the definition of superfluidity and the characteristic observables in a nonequilibrium context, e.g., extension of the standard Landau critical velocity has been proposed [11,12,[25][26][27][28][29]. Novel kinds of nonlinear excitations have also been observed in recent experiments, such as the oblique dark solitons and vortices [30][31][32], or bright spatial and temporal solitons [33].…”

Interaction between an Impurity and Nonlinear Excitations in a Polariton Condensate

“…In his seminal paper [ 1 , 2 ], Landau first studied an electron dressed by phonons. Since then, such impurity problem has appeared in different incarnations, such as the Kondo [ 3 ] and Cherenkov [ 4 , 5 , 6 ] effects, the polaron physics [ 7 ], and the Landau criterion [ 8 , 9 , 10 , 11 , 12 ] for the sound speed of a superfluid. At present, there are great efforts and interest in studying a mobile impurity in a quantum medium in diverse areas [ 13 , 14 , 15 , 16 , 17 , 18 , 19 ].…”

“…Central to understanding the dynamics of an impurity in a quantum many-body medium is to include the entanglement between the impurity and the surrounding excitations on a wide range of energy scales. To achieve this task, one needs to consider the impurity’s effective mass as being finite, instead of infinite [ 8 , 9 , 10 , 11 , 12 ]. In addition, the excitations surrounding the impurity can be linear or nonlinear excitations.…”