Superluminal X-waves in a polariton quantum fluid  

作　　者：Antonio Gianfrate Lorenzo Dominici Oksana Voronych Michał Matuszewski Magdalena Stobińska Dario Ballarini Milena De Giorgi Giuseppe Gigli Daniele Sanvitto 

机构地区：[1]CNR NANOTEC,Istituto di Nanotecnologia,Via Monteroni,73100 Lecce,Italy [2]Institute of Theoretical Physics and Astrophysics,University of Gdańsk,ul.Wita Stwosza 57,80-952 Gdańsk,Poland [3]Institute of Physics,Polish Academy of Sciences,Al.Lotników 32/46,02-668 Warsaw,Poland [4]Faculty of Physics,University of Warsaw,Pasteura 5,02-093 Warsaw,Poland [5]INFN,sezione di Lecce,73100 Lecce,Italy

出　　处：《Light(Science & Applications)》2017年第1期311-319,共9页光（科学与应用)（英文版）

基　　金：supported by the European Research Council POLAFLOW Grant 308136 and the Italian MIUR project Beyond Nano;supported by the NCN Grant no.2012/04/M/ST2/00789;MNiSW Iuventus Plus project no.IP 2014044873;support from the FNP project FIRST TEAM/2016-2/17;support from NCN Grant 2015/17/B/ST3/02273.

摘　　要：In this work,we experimentally demonstrate for the first time the spontaneous generation of two-dimensional exciton-polariton X-waves.X-waves belong to the family of localized packets that can sustain their shape without spreading,even in the linear regime.This allows the wavepacket to maintain its shape and size for very low densities and very long times compared to soliton waves,which always necessitate a nonlinearity to compensate the diffusion.Here,we exploit the polariton nonlinearity and uniquely structured dispersion,comprising both positive-and negative-mass curvatures,to trigger an asymmetric four-wave mixing in momentum space.This ultimately enables the self-formation of a spatial X-wave front.Using ultrafast imaging experiments,we observe the early reshaping of the initial Gaussian packet into the X-pulse and its propagation,even for vanishingly small densities.This allows us to outline the crucial effects and parameters that drive the phenomena and to tune the degree of superluminal propagation,which we found to be in close agreement with numerical simulations.

关 键 词：negative mass NONLINEARITY POLARITONS SUPERLUMINAL X-waves 

分 类 号：O41[理学—理论物理]