CondMat for Dummies: The BKT transition with and without long-range couplings

Datum

20.03.2026

Zeit

17:00 - 18:00

Sprecher

Luis Walther

Zugehörigkeit

MPIPKS

Sprache

en

Hauptthema

Physik

Andere Themen

Physik

Beschreibung

The Berezinskii–Kosterlitz–Thouless (BKT) transition in the two-dimensional XY model stands as the first example of a topological phase transition outside of the celebrated Landau paradigm. In this talk, I will first introduce the XY model and provide an intuitive derivation of the BKT transition based on a Landau–Peierls–type argument. This perspective highlights how spin waves destabilize long-range order and how the decoupling of vortices drives a qualitatively new type of phase transition. Further, I will turn to a more realistic setting by incorporating long-range interactions, which are frequently encountered in experimental systems. I will analyze the effect of long-range interactions on the model and argue that the essential features of the BKT transition remain robust, persisting even in the presence of arbitrary long-range interactions.

Letztmalig verändert: 19.03.2026, 07:36:24