Probing supersolidity through excitations in a spin-orbit-coupled Bose-Einstein condensate

Spin-orbit-coupled Bose-Einstein condensates are a flexible experimental platform to engineer synthetic quantum many-body systems. In particular, they host the so-called stripe phase, an instance of a supersolid state of matter. The peculiar excitation spectrum of the stripe phase, a definite footprint of its supersolidity, had so far remained out of experimental reach. In my talk, I will present recent experiments where we achieve in situ imaging of the stripes and directly observe both superfluid and crystal excitations using a matter-wave optics magnification scheme. We exploit the resulting images to investigate superfluid hydrodynamics and reveal a stripe compression mode, thus demonstrating that the system possesses a compressible crystalline structure. Through the frequency softening of this mode, we locate the supersolid transition point. Our results establish spin-orbit-coupled supersolids as ideal systems to investigate supersolidity and its rich dynamics.