Terahertz Resonant Emission by Optically Excited Infrared-Active Shear Phonons in KY(MoO).

The generation of monochromatic electromagnetic radiation in the terahertz (THz) frequency range has remained a challenging task for many decades. Here, the emission of monochromatic sub-THz radiation by optical phonons in the dielectric material KY(MoO) is demonstrated. The layered crystal structure of KY(MoO) causes infrared-active shear lattice vibrations to have energies below 3.

Pressure-Induced Changes in the Crystal Structure and Electrical Conductivity of GeVS.

Lacunar spinels, represented by AMX compounds (A = Ga or Ge; M = V, Mo, Nb, or Ta; X = S or Se), form a unique group of ternary chalcogenide compounds. Among them, GeVS has garnered significant attention due to its distinctive electrical and magnetic properties. While previous research efforts have primarily focused on studying how this material behaves under cooling conditions, pressure is another factor that determines the state and characteristics of solid matter.

Magnetization reversal through an antiferromagnetic state.

Magnetization reversal in ferro- and ferrimagnets is a well-known archetype of non-equilibrium processes, where the volume fractions of the oppositely magnetized domains vary and perfectly compensate each other at the coercive magnetic field. Here, we report on a fundamentally new pathway for magnetization reversal that is mediated by an antiferromagnetic state. Consequently, an atomic-scale compensation of the magnetization is realized at the coercive field, instead of the mesoscopic or macroscopic domain cancellation in canonical reversal processes.

Broadband magnetic resonance spectroscopy in MnSc[Formula: see text]S[Formula: see text].

Recent neutron scattering experiments suggested that frustrated magnetic interactions give rise to antiferromagnetic spiral and fractional skyrmion lattice phases in MnSc[Formula: see text]S[Formula: see text] . Here, to trace the signatures of these modulated phases, we studied the spin excitations of MnSc[Formula: see text]S[Formula: see text] by THz spectroscopy at 300 mK and in magnetic fields up to 12 T and by broadband microwave spectroscopy at various temperatures up to 50 GHz. We found a single magnetic resonance with frequency linearly increasing in field.

Dressed j-1/2 objects in mixed-valence lacunar spinel molybdates.

The lacunar-spinel chalcogenides exhibit magnetic centers in the form of transition-metal tetrahedra. On the basis of density-functional computations, the electronic ground state of an Mo tetrahedron has been postulated as single-configuration a e t, where a, e, and t are symmetry-adapted linear combinations of single-site Mo t atomic orbitals. Here we unveil the many-body tetramer wave-function: we show that sizable correlations yield a weight of only 62% for the a e t configuration.

How Correlations and Spin-Orbit Coupling Work within Extended Orbitals of Transition-Metal Tetrahedra of 4d/5d Lacunar Spinels.

Spin-orbit quartet ground states are associated with rich phenomenology, ranging from multipolar phases in f rare-earth borides to magnetism emerging through covalency and vibronic couplings in d transition-metal compounds. The latter effect has been studied since the 1960s on t octahedral units in both molecular complexes and extended solid-state lattices. Here we analyze the = 3/2 quartet ground state of larger cubane-like entities in lacunar spinels, composed of transition-metal () tetrahedra caged by chalcogenide ligands ().

Ultra-robust high-field magnetization plateau and supersolidity in bond-frustrated MnCrS.

Frustrated magnets provide a promising avenue for realizing exotic quantum states of matter, such as spin liquids and spin ice or complex spin molecules. Under an external magnetic field, frustrated magnets can exhibit fractional magnetization plateaus related to definite spin patterns stabilized by field-induced lattice distortions. Magnetization and ultrasound experiments in MnCrS up to 60 T reveal two fascinating features: (i) an extremely robust magnetization plateau with an unusual spin structure and (ii) two intermediate phases, indicating possible realizations of supersolid phases.