The MCQST Colloquium Series features interdisciplinary talks given by visiting international speakers. The monthly colloquium covers topics spanning all MCQST research units and will be broadcast live via Zoom for audiences worldwide. The main goal of the series is to create the framework for idea exchange, to strengthen links with QST leading groups worldwide, as well as to act as an integral part of the local educational environment.

MCQST Colloquium: Jean Dalibard

We are excited to invite you to the colloquium talk by Jean Dalibard (École Polytechnique).

Agenda

14:00 | Teaser talk by Robin Groth on TBA

14:15 | Coffee break

14:30 | Colloquium talk by Jean Dalibard on “Coherence and Superfluidity: The Two Sides of the Same Coin, really?”

Coherence and Superfluidity: The Two Sides of the Same Coin, really?

In 1925, Einstein predicted that an ideal gas would undergo a phase transition once its density crosses a threshold, with particles condensing into a single quantum state and establishing macroscopic coherence. The subsequent discovery of superfluidity in helium appeared to confirm this prediction, but are coherence and superfluidity truly equivalent?

Experiments with ultracold atoms reveal that superfluidity can exist without long-range coherence, as in low-dimensional fluids, while a fully coherent fluid may exhibit only partial superfluidity—a phenomenon anticipated in the 1970s by Leggett. Today, the question of determining the superfluid fraction of a Bose–Einstein condensate has gained renewed importance with the realization of supersolids in dipolar atomic gases. In this presentation, I will discuss recent experiments that address this fundamental issue in spatially modulated quantum systems.

About Jean Dalibard

Jean Dalibard completed his graduate studies under the supervision of Claude Cohen-Tannoudji, and then spent the first part of his career at the CNRS. Since 2012, he is a professor at the Collège de France, where he holds the chair "Atoms and Radiation".

His first research topics concerned the elucidation of mechanisms for cooling and trapping atoms (Sisyphus cooling, magneto-optical trap), and he also contributed to the development of the quantum trajectory approach. His current research focuses on ultracold matter. Among his achievements in this field are the observation of quantum vortices in rotating condensates, the observation of a Kosterlitz-Thoulesstransition in a 2D fluid, and the generation of artificial gauge fields for quantum gases made of neutral atoms.

Join in-person or via Zoom

https://lmu-munich.zoom.us/j/69761439704
Meeting ID: 697 6143 9704, Passcode: mcqst2526