Themes

A quantum spin liquid (QSL) is an exotic quantum state of matter that does not exhibit conventional magnetic order, even at absolute zero. The concept was first proposed by P. W. Anderson in 1973.

In ordinary magnetic materials, electron spins tend to align in an ordered pattern as the temperature approaches absolute zero, forming conventional magnetic order. In contrast, spins in a quantum spin liquid remain in a highly disordered, dynamically fluctuating state even at absolute zero. This behavior typically arises from a combination of geometric frustration—for example, competing antiferromagnetic interactions on triangular or kagome lattices, where spins cannot simultaneously satisfy all neighboring antiparallel alignment requirements—and strong quantum fluctuations. The spins are also strongly quantum-entangled, meaning that their properties are intrinsically correlated across the system. When an energy perturbation is introduced, a quantum spin liquid does not necessarily respond by producing conventional spin waves (magnons). Instead, its excitations can fractionalize into quasiparticles such as spinons, which carry fractional quantum numbers and can propagate independently.

Quantum spin liquids provide an ideal platform for exploring many-body quantum physics and offer important opportunities for understanding high-temperature superconductivity and developing quantum computing technologies.