Dynamics play an essential role in the investigation of quantum materials and matter. In this special issue, multiple facets of dynamic quantum matter are investigated and examined. The cover image shows a photon on a Dirac cone, which illustrates the interaction between photons and electrons to produce dynamic states. (Image created by Bart Olsthoorn)

Dynamics play an important role in the investigation of electronic and magnetic materials and matter. In article number 1900350, Daniel Boyko, Avadh Saxena, and Jason T. Haraldsen examine the spin-wave dynamics for the 2D Kagome lattice. The cover image shows the dramatic change in the energy dispersion across the Brillouin zone for the 120° phase for the 2D Kagome lattice, which produces a single mode due to honeycomb symmetry produced by spins pointing in and out of the Kagome triangles.

The concept of the time-independent correlators for the even- and odd-frequency pairing states defined for both bosonic and fermionic quasiparticles is proposed. These correlators explicitly capture the existence of two distinct classes of pairing states and provide a direct probe of the hidden Berezinskii order. This concept is illustrated for Majorana fermions and quasiparticles in Dirac semimetals.

A growing body of evidence suggests that interband quasiparticle scattering in multiband superconductors can give rise to exotic odd-frequency Cooper pairs. Here, the fundamental physics associated with the generation of odd-frequency pairing in multiband superconductors is highlighted and several examples of contemporary systems are discussed in which this kind of pairing is expected to be realized.

In van der Waals heterostructures the constituent layers and their stacking are not constrained by chemical laws. This freedom allows the realization of van der Waals systems with unique electronic properties, such as twisted bilayer graphene. Herein, recent advances on the study of van der Waals systems in which at least one layer has strong spin orbit coupling are reviewed.

A new approach to obtain the classical analogs of the quantum metric tensor and the Berry curvature for classical integrable systems is presented. Illustrative examples of bosonic and fermionic systems are given and the results are compared with their quantum counterpart. The classical expressions contain almost all the structure of the parameter space associated with the quantum system.

The spin dynamics for various magnetic configurations arranged on a Kagome lattice are investigated and the production of bosonic Dirac and Weyl nodes in the spin-wave spectra is demonstrated. Additionally, a connection to the asymmetric properties of the Kagome lattice and the antiferromagnetic configurations is discerned and the presence of flat modes in the spectra that are characteristic of cluster excitations is shown.

A recent proposal for transient excitonic condensate in optically pumped Dirac materials is reviewed in the context of a broader search for dynamically induced quantum states of matter. A unified theoretical framework for describing transient excitonic states in 2D and 3D Dirac materials is developed and model predictions for real materials are analyzed within this common framework.

Dilute coatings of transition metal adatoms may be a path toward inducing a non-trivial spin–orbit coupling in graphene. Here, electronic transport measurements on osmium-decorated graphene find that Os adatoms donate holes into graphene rather than electrons as expected.

The transport properties and electron states in nanowires of Dirac and Weyl semimetals are studied paying special attention to the structure and properties of the surface Fermi arcs. It is found that the spatial profile of the direct current conductivity is nontrivial and it can be much higher at the surface than in the bulk.

The realization of various hybrid Dirac and Weyl phases in a 3D Luttinger semimetal with quadratic band touching (QBT) is investigated. Employing two examples of nonuniform periodic kicking, a dynamical way to realize a unique hybrid dispersion Dirac semimetal with coexisting linear and quadratic nodes is proposed. Next, by tilting QBT in presence of an external magnetic field different single/double hybrid Weyl semimetals are realized.

Interplay between Weyl electrons and nonuniform magnetic textures in magnetic Weyl semimetals is reviewed. The key idea is the fictitious “axial gauge fields,” which effectively describes the influence of magnetic textures on the Weyl electrons, modifying the electronic spectra and transport properties. The effect of magnetic domain walls is discussed as an example.

Quantum effects on the dynamics of ions are usually reserved for light elements such as hydrogen and helium and their effects have been predicted to alter the critical temperature at which structural transformations occur in bulk ferroelectric materials, too. The aim, herein, is to indicate that such quantum effects must also be present in some 2D materials with structural degeneracies.