2019/04/30 by Zoe Z. Yan, Yiqi Ni, Carsten Robens +1 · 2 citations
Physics and Astronomy · #cond-mat.quant-gas #physics.atom-ph #quant-ph
paper · pdf · doi:10.1126/science.aax5850
published as Science, 368, 190-194 (2020) · 17 pages, 14 figures
arxiv created 2019/09/06 · arxiv updated 2020/04/16
The emergence of quasiparticles in strongly interacting matter represents one of the cornerstones of modern physics. However, when different phases of matter compete near a quantum critical point, the very existence of quasiparticles comes under question. Here we create Bose polarons near quantum criticality by immersing atomic impurities in a Bose-Einstein condensate (BEC) with near-resonant interactions. Using locally-resolved radiofrequency spectroscopy, we probe the energy, spectral width, and short-range correlations of the impurities as a function of temperature. Far below the superfluid critical temperature, the impurities form well-defined quasiparticles. However, their inverse lifetime, given by their spectral width, is observed to increase linearly with temperature at the Planckian scale (kB T)/(ℏ), a hallmark of quantum critical behavior. Close to the BEC critical temperature, the spectral width exceeds the binding energy of the impurities, signaling a breakdown of the quasiparticle picture.