meVscale

meV scale refers to energy features in the milli-electronvolt range (approximately 10^-3 eV). This low-energy regime is central to many phenomena in condensed matter physics, especially at cryogenic temperatures where thermal energy k_B T is comparable to or smaller than a few meV. The meV scale sets the resolution for many low-energy excitations and gaps, such as superconducting gaps, magnons, and phonon anomalies.

In practice, meV-scale physics appears in superconductors (gap magnitudes of a few meV), magnets (magnon dispersions), and two-dimensional materials where small spin-orbit splittings or near-Fermi-level features shape electronic structure. It also appears in charge- and spin-density waves and in quantum-confined systems like quantum dots, where energy level spacings are typically in the meV range. This scale governs low-energy quasiparticles and collective modes across a variety of quantum materials, including topological insulators and oxide compounds.

Common experimental probes with meV resolution include angle-resolved photoemission spectroscopy (ARPES) for band structure near the Fermi level, scanning tunneling spectroscopy (STS) for local density of states, and inelastic neutron scattering for magnetic excitations, as well as Raman and terahertz spectroscopy for vibrational and spin-related modes. Achieving sufficient resolution often requires cryogenic temperatures to suppress thermal broadening (k_B T of a few meV or less) and high-precision instrumentation.

The meV scale remains a focal point in research on superconductivity, magnetism, and other quantum phenomena, guiding material design and the interpretation of low-energy excitations while presenting challenges related to instrumental limits and disorder.