NUM division - Publication Highlights

The description and detection of unconventional magnetic states, such as spin liquids, is a recurring topic in condensed matter physics. While much of the efforts have traditionally been directed at geometrically frustrated antiferromagnets, recent studies reveal that systems featuring competing antiferromagnetic and ferromagnetic interactions are also promising candidate materials.

Since the seminal ideas of Berezinskii, Kosterlitz and Thouless, topological excitations have been at the heart of our understanding of a whole novel class of phase transitions. In most cases, those transitions are controlled by a single type of topological objects. There are, however, some situations, still poorly understood, where two dual topological excitations fight to control the phase diagram and the transition.

Quantum spin liquid is a disordered but highly entangled magnetic state with fractional spin excitations. The ground state of an exactly solved Kitaev honeycomb model is perhaps its clearest example. Under a magnetic field, a spin flip in this model fractionalizes into two types of anyon, a quasiparticle with more complex exchange statistics than standard fermions or bosons: a pair of gauge fluxes and a Majorana fermion.

In recent years, intriguing hints for the violation of lepton flavor universality (LFU) have been accumulated in semileptonic B decays, both in the charged-current transitions b → cl^-ν^-_l (i.e., R_D, R_D∗, and R_J/Ψ and the neutral-current transitions b → sl⁺l^- (i.e., R_K and R_K∗.

Motivated by recent experimental observations in α-RuCl₃, we study the Κ-Γ model on the honeycomb lattice in an external magnetic field. By a slave-particle representation and variational Monte Carlo calculations, we reproduce the phase transition from zigzag magnetic order to a field-induced disordered phase. The nature of this state depends crucially on the field orientation.

In a quantum spin liquid, the magnetic moments of the constituent electron spins evade classical long-range order to form an exotic state that is quantum entangled and coherent over macroscopic length scales. Such phases offer promising perspectives for device applications in quantum information technologies, and their study can reveal new physics in quantum matter.

The integration of nanoparticles with proteins is of high scientific interest due to the amazing potential displayed by their complexes, combining the nanoscale properties of nanoparticles with the specific architectures and functions of the protein molecules.

The ligand shell (LS) determines a number of nanoparticles’ properties. Nanoparticles’ cores can be accurately characterized; yet the structure of the LS, when composed of mixture of molecules, can be described only qualitatively (e.g., patchy, Janus, and random).

The CP asymmetry in τ → K_Sπν_τ, as measured by the BABAR collaboration, differs from the standard model prediction by 2.8 σ. Most nonstandard interactions do not allow for the required strong phase needed to produce a nonvanishing CP asymmetry, leaving only new tensor interactions as a possible mechanism.