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- Lectures
- Institute of Atomic and Molecular Sciences
- Location
4F, C.T.Chang Memorial Hall，Institute of Atomic and Molecular Sciences (NTU Campus)
- Speaker Name
Prof. Chih-Chun Chien(University of California, USA)
- State
Definitive
- Url
BCS-BEC Crossover and XY Model on Spherical Shell
2022-07-01 11:00 - 12:00
Abstract
| I will discuss geometric effects on quantum and classical systems with strong interactions by contrasting some examples on a 2D plane and a spherical shell. The quantum example is the BCS-Bose Einstein condensation (BEC) crossover of atomic fermions in a spherical bubble trap. Following the BCS-Leggett theory, the equations of state of a two-component Fermi gas on a spherical shell resemble those on a 2D plane. Therefore, the conventional BCS-BEC crossover can be induced by increasing the interaction. Nevertheless, there is another BCS-BEC crossover on a spherical shell induced by curvature when the interaction is fixed, which is made possible by the 2D two-body binding energy and the compact geometry. The classical example is the XY model on an almost uniform lattice on a spherical surface known as the Fibonacci lattice. Due to the Poincare-Hopf theorem, the net vortex charge is finite on a spherical surface but vanishes on a 2D plane. By using machine learning methods, we identify patterns of vortices and antivortices, locate the Berezinskii-Kosterlitz-Thouless transition, and trace the dynamics of vortices and antivortices of the spherical XY model. | ||||||||
