In condensed matter physics, some of the most surprising behavior appears only when many quantum particles interact as a group. Individual quantum spins can behave predictably on their own, but when they influence one another, entirely new effects emerge. Explaining how these spins interact collectively is a core goal of modern physics because it helps scientists understand the deeper rules governing quantum matter.
One of the most influential collective effects is the Kondo effect, which describes how localized spins interact with mobile electrons. This interaction plays a key role in shaping the behavior of many quantum materials.\
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