Research: Novel type of quantum critical point in metallic environment

A deconfined quantum critical point denotes an exotic quantum transition between two different types of long-range orders. It breaks the Landau paradigm of conventional phase transitions and is usually associated with the emergence of novel fractionalized degrees of freedom. Such behavior has previously been heavily discussed in the context of insulating magnets.

Research performed within SFB 1143 in collaboration with the Julius-Maximilians-Universität of Würzburg has now identified a new candidate for a deconfined quantum critical point in a system that is typically not associated with such behavior: a semimetal. Numerical data from large-scale quantum Monte Carlo simulations are consistent with the interpretation of a direct continuous order-to-order transition between a gapless Dirac semimetal and a fully gapped state. The result arguably represents the first lattice realization of a deconfined quantum critical point featuring gapless fermionic degrees of freedom.

This research has been published in Physical Review Letters as "Editors' Suggestion."

Z. H. Liu, M. Vojta, F. F. Assaad, L. Janssen,
Metallic and deconfined quantum criticality in Dirac systems,
Phys. Rev. Lett. 128, 087201 (2022) (arXiv)