Recent Highlight: 

Quantum transport of charge have revealed a wealth of quantum phases such as FQAHE and superconductivity. Yet, many other exotic quantum states in 2D flatland hosts charge-neutral modes, remaining more challenging to probe transport experimentally. One example is intervalley coherent (IVC) states, a unifying theme in graphene and semiconductor moire systems, predicted to host a neutral Goldstone mode arising from spontaneously broken valley U(1) symmetry. Here we directly image the transport of collective valley modes in twisted WSe2 using an ultrafast imaging technique. Near the van Hove singularity, we uncover two new propagating collective modes with different velocities. One mode propagates at a large speed of ~3 km/s and is consistent with the Goldstone mode of an IVC state, while the slower mode is likely a gapped excitation. These can be interpreted as the phase and amplitude modes of a spin-valley superfluid. Our study opens new opportunities to study the transport of charge neutral modes in condensed matter systems. (Read more: arXiv: 2507.18770 (2025))

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