Physicists Find Resistivity Cap in Metals at U/t 6 Using Ultracold Potassium Atoms
Updated
Updated · The Brighter Side of News · Jun 18
Physicists Find Resistivity Cap in Metals at U/t 6 Using Ultracold Potassium Atoms
2 articles · Updated · The Brighter Side of News · Jun 18
Summary
Ultracold potassium-40 atoms in a laser-made lattice showed that stronger collisions stop raising electrical resistivity once interactions reached the strongly coupled regime, revealing an upper limit to collision-driven resistance.
Conductivity broadened sharply as interaction strength rose from about U/t = 1 to U/t = 4, but pushing it to roughly U/t = 6 added almost no further dissipation, defying the usual U-squared expectation.
The team traced the flattening to a bounded scattering amplitude in the lattice—"lattice unitarity"—which shifts transport from interaction-limited to tunneling-limited dissipation; even at the strongest coupling, the dissipation rate reached only about one-third of that bound.
A kinetic-theory model using the full two-body transition matrix matched the measurements without free transport parameters, helping isolate the effect from changes in effective mass or static susceptibility.
Because the optical lattice removes phonons, disorder and structural changes, the result offers a cleaner benchmark for interpreting transport in low-density, strongly interacting metals and other quantum materials.