Polaron chemistry: fate of an impurity in a Bose Einstein condensate and induced local quantum phase transitions
IQOQI Quantum SeminarSpeaker: Richard Schmidt
When: Mar. 22 2023 09:00
Where: Erwin Schrödinger Saal
In ultracold atomic gases, a unique interplay arises between phenomena known from condensed matter, few-body physics and chemistry. Similar to an electron in a solid, a quantum impurity in an atomic Bose-Einstein condensate is dressed by excitations from the medium, forming a polaron quasiparticle, the Bose polaron, with modified properties. At the same time, the atomic impurity can undergo the chemical reaction of three-body recombination with atoms from the BEC, which can be resonantly enhanced due to universal three-body Efimov bound states crossing the continuum. In this talk we will discuss how Bose polarons provide an intriguing example of chemistry in a quantum medium, by shifting such three-body recombination resonances to smaller interaction strengths due to participation of the polaron cloud in bound state formation. Simultaneously, the shifted Efimov resonance marks the onset of a polaronic instability towards the decay into larger Efimov clusters and fast recombination, offering a remarkable example of how chemistry can be modified in a quantum medium. Finally we discuss how single quantum impurities can induce local quantum phase transitions in a many-body system bringing together concepts from chemistry and statistical physics.