The Joint Condensed Matter Seminar (JCMS) series is organised by KTH Royal Insitute of Technology, Nordita, and Stockholm University.
On Thursday, April 24th, 2025 from 11.00 am to 12.00 we will host a seminar by Andrea Bianchi from Université de Montréal.
Quantum Spin Liquids: What They Are and Why They Are So Hard to Find
Quantum spin liquids (QSLs) are a fascinating class of topological quantum states. The study of such states began with the discovery of the quantum Hall effect (QHE) in 1980, followed by the fractional quantum Hall effect (FQHE) in 1982. These discoveries introduced a new way of classifying matter based on topology rather than traditional symmetry breaking. Unlike conventional phase transitions—such as ferromagnetism, where an order parameter emerges—topological states can transition between phases without breaking symmetry. This shift in perspective has led to a range of discoveries, from topological insulators to QSLs in frustrated magnets.
In this talk, I will explore the ongoing search for QSLs, using Ce₂Zr₂O₇ as a key example. I will begin by distinguishing classical magnetic order, such as ferromagnetism, from the quantum mechanically entangled ground state of a QSL. I will then introduce the concept of magnetic frustration, which prevents classical magnetic order from forming, and discuss the role of quantum fluctuations in stabilizing QSLs.