millielectronvolts

Millielectronvolt (meV) is a unit of energy used in physics. It is one thousandth of an electronvolt (eV), where 1 eV equals 1.602176634e-19 joule, so 1 meV equals 1.602176634e-22 joule.

In condensed matter physics and related fields, the meV scale is convenient for low-energy excitations such as superconducting gaps, phonons, and magnons, as well as electronic features near the Fermi level. Many experiments and theoretical models in nanoscale systems report energies in meV, reflecting the typical energies of electrons and quasiparticles in solids.

The relation to frequency and temperature follows E = h f, with Planck’s constant h ≈ 4.135667696e-15 eV·s. Therefore, 1 meV corresponds to about 0.2417 terahertz. The Boltzmann constant k_B is about 8.617333262e-5 eV/K, so room temperature (~300 K) gives k_B T ≈ 25.9 meV, illustrating why thermal excitations are significant at this energy scale. Conversely, 1 THz is roughly 4.14 meV.

Comparisons: 1 meV = 10^-3 eV, and 1 THz ≈ 4.14 meV. These energies are far smaller than the electron rest mass energy (511 keV) but are typical for quantum phenomena and solid-state physics.

Examples of meV-scale values include superconducting gaps on the order of 1–10 meV and phonon energies in crystals that often lie in the meV range. The meV unit thus provides a practical scale for many experimental measurements and theoretical descriptions in modern physics.