Quantumkritisches

Quantumkritisches is an adjective used in physics, primarily in German-language literature, to describe phenomena associated with quantum criticality. It refers to properties, regimes, or systems in the vicinity of a quantum critical point (QCP), a zero-temperature continuous phase transition driven by quantum fluctuations. By tuning a control parameter such as pressure, chemical composition, or magnetic field, the ground state can be driven from one ordered phase to another; at the QCP, fluctuations in space and time become scale-invariant, leading to characteristic power-law behavior and often a breakdown of conventional Fermi-liquid theory.

In the quantum-critical regime, observable quantities exhibit anomalous scaling with temperature and energy. Typical signatures include non-Fermi-liquid transport (for example, resistivity that deviates from the standard quadratic temperature dependence), enhanced or nontrivially behaving specific heat, and unusual magnetic or spin-dynamic responses. The theoretical framework commonly employs renormalization group methods and scaling hypotheses, with a dynamical critical exponent z describing how time scales with length, and a correlation length exponent ν.

Experimentally, quantum-critical behavior is studied in a variety of strongly correlated materials, including heavy-fermion metals such as CeCu6−xAux and YbRh2Si2, as well as certain cuprates, iron-based superconductors, and organic conductors. Researchers use tuning parameters to map phase diagrams and identify quantum-critical regions, aiming to understand non-Fermi-liquid behavior, unconventional superconductivity, and the interplay between magnetism and electronic correlations.

The term is used in German texts as quantumkritisches, while English literature typically uses "quantum-critical" or "quantum critical" as the adjective. See also quantum phase transition, quantum critical point, non-Fermi liquid, scaling theory.