The dance floor where magnetic moments and conduction electrons take turns leading and following: that is the Kondo lattice in the crystal V5S8. At ambient pressure, this layered vanadium sulfide exhibits an antiferromagnetic transition at 32 K: spins align in antiphase, and conduction electrons form a Fermi liquid with a quadratic temperature dependence of resistance. The Sommerfeld coefficient γ ≈ 70 mJ/(mol·K²) and the coefficient A ≈ 6×10⁻² μΩ·cm/K² indicate an effective mass enhancement of 3–5 times compared to DFT calculations. These are heavy quasiparticles: electrons dressed in a cloud of spin fluctuations.

Pressure changes the music. In a Bridgman cell, where the crystal is compressed to 10 GPa, which is about a hundred thousand times atmospheric pressure, the Néel temperature gradually decreases up to 9 GPa and then drops sharply. Simultaneously, the exponent n in the resistance law ρ = ρ₀ + ATⁿ decreases from 2 to 1. The Fermi liquid is destroyed: instead of a quadratic dependence, resistance becomes linear. This non-Fermi liquid behavior is a hallmark of a quantum critical point, a phase transition at zero temperature driven by quantum fluctuations.

Previously, it was thought that quantum criticality required f-electrons: the heavy inner shells of lanthanides and actinides. The work on V5S8 shows for the first time that d-electrons of transition metals can also create a Kondo lattice with a critical point. This extends the Doniach diagram to systems with narrow d-bands and challenges the established view. What happens at pressures above 10 GPa? Do heavy quasiparticles persist there, or does a new non-Fermi liquid phase emerge? Answers will require neutron diffraction under pressure and resistance measurements under more extreme conditions.

The dance floor is not empty. The music has become quieter, but the dancers, the magnetic moments and conduction electrons, continue to move, now without a leader. The quantum critical point in V5S8 reminds us that the boundaries between states of matter are blurred, and pressure can rewrite the rules even for seemingly well-understood materials.