spinstabiel

Spinstabiel is a term used in some Dutch-language physics literature to describe a system or state whose spin is not stable over time due to interactions with its environment. The term is less common in English-language sources, where phrases such as spin relaxation or spin decoherence are more typical. In broad use, spinstabiel refers to scenarios where a spin state loses its orientation or coherence, returning toward thermal equilibrium or becoming a mixed state.

In quantum mechanics, spin is an intrinsic form of angular momentum with a fixed magnitude but a direction that can change under external fields or internal interactions. A spin described as unstable is one that relaxes or decoheres rapidly, diminishing polarization or quantum coherence.

Several mechanisms can drive spin instability. Magnetic-field noise and fluctuations can randomize spin orientation. Spin-orbit coupling links spin to orbital motion, allowing environmental perturbations to affect spin. Hyperfine interactions with nearby nuclear spins, dipole-dipole couplings between spins, and coupling to lattice vibrations (phonons) also contribute to relaxation and dephasing. In nanoscale devices such as quantum dots, nitrogen-vacancy centers in diamond, or donor spins in semiconductors, these processes set the achievable spin lifetimes and coherence times.

Spinstabiel has practical implications for applications in nuclear magnetic resonance (NMR), electron spin resonance (ESR), spintronics, and quantum computing, where long spin lifetimes and high coherence are desirable. It is typically quantified by relaxation times T1 (longitudinal) and T2 (transverse); shorter times indicate greater instability. In nuclear physics, metastable spin states can arise in certain isomers, decaying to lower-spin configurations.

See also: spin relaxation, spin decoherence, quantum coherence, spin qubits.