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Exchange-antisymmetric pair wavefunctions in fermionic systems can give rise to unconventional superconductors and superfluids 1 – 3 . The realization of these states in controllable quantum systems, such as ultracold gases, could enable new types of quantum simulations 4 – 8 , topological quantum gates 9 – 11 and exotic few-body states 12 – 15 . However, p -wave and other antisymmetric interactions are weak in naturally occurring systems 16 , 17 , and their enhancement via Feshbach resonances in ultracold systems has been limited by three-body loss 18 – 24 . Here we create isolated pairs of spin-polarized fermionic atoms in a multiorbital three-dimensional optical lattice. We spectroscopically measure elastic p -wave interaction energies of strongly interacting pairs of atoms near a magnetic Feshbach resonance. The interaction strengths are widely tunable by the magnetic field and confinement strength, and yet collapse onto a universal curve when rescaled by the harmonic energy and length scales of a single lattice site. The absence of three-body processes enables the observation of elastic unitary p -wave interactions, as well as coherent oscillations between free-atom and interacting-pair states. All observations are compared both to an exact solution using a p -wave pseudopotential and to numerical solutions using an ab initio interaction potential. The understanding and control of on-site p -wave interactions provides a necessary component for the assembly of multiorbital lattice models 25 , 26 and a starting point for investigations of how to protect such systems from three-body recombination in the presence of tunnelling, for instance using Pauli blocking and lattice engineering 27 , 28 . The authors measure elastic p -wave interaction energies in pairs of fermionic atoms occupying the lowest two orbitals of an optical lattice; isolation of individual pairs of atoms protects against three-body recombination, enabling a theoretical maximum of interaction energy to be achieved.

We investigate the interaction-induced resistivity of ultracold fermions in a three-dimensional optical lattice. In situ observations of transport dynamics enable the determination of real and imaginary resistivity. In the strongly interacting metallic regime, we observe a striking saturation of the current-dissipation rate towards a value that is independent of the interaction strength. This phenomenon is quantitatively captured by a dissipation model that uses a renormalized two-body scattering matrix. We further measure the temperature dependence of resistivity in the strongly interacting limit and discuss the predicted asymptotic high-temperature behavior. Our results provide a clear microscopic understanding of bounded resistivity of low-density metals, thus providing a useful benchmark for studies of strongly correlated atomic and electronic systems.

We investigate the interaction-induced resistivity of ultracold fermions in a three-dimensional optical lattice. In situ observations of transport dynamics enable the determination of real and imaginary conductivity (or resistivity). In the strongly interacting metallic regime, we observe a striking saturation of the current-dissipation rate to a value independent of the interaction strength. This behavior is quantitatively captured by a dissipation model that uses a renormalized two-body scattering matrix. The highest observed dissipation rates approach, but do not reach, the unitarity bound on two-body scattering in the lattice, owing to momentum dispersion. We further measure the temperature dependence of resistivity in the strongly interacting limit and compare it to the predicted asymptotic behaviors. These results provide a clear microscopic understanding of bounded resistivity of low-density metals, thus providing a useful benchmark for studies of strongly correlated atomic and electronic systems.

Exchange-antisymmetric pair wavefunctions in fermionic systems can give rise to unconventional superconductors and superfluids with non-trivial transport properties. The realisation of these states in controllable quantum systems, such as ultracold gases, could enable new types of quantum simulations, topological quantum gates, and exotic few-body states. However, p-wave and other antisymmetric interactions are weak in naturally occurring systems, and their enhancement via Feshbach resonances in ultracold systems has been limited by three-body loss. In this work, we create isolated pairs of spin-polarised fermionic atoms in a multi-orbital three-dimensional optical lattice. We spectroscopically measure elastic p-wave interaction energies of strongly interacting pairs of atoms near a magnetic Feshbach resonance and find pair lifetimes to be up to fifty times larger than in free space. We demonstrate that on-site interaction strengths can be widely tuned by the magnetic field and confinement strength but collapse onto a universal single-parameter curve when rescaled by the harmonic energy and length scales of a single lattice site. Since three-body processes are absent within our approach, we are able to observe elastic unitary p-wave interactions for the first time. We take the first steps towards coherent temporal control via Rabi oscillations between free-atom and interacting-pair states. All experimental observations are compared both to an exact solution for two harmonically confined atoms interacting via a p-wave pseudopotential, and to numerical solutions using an ab-initio interaction potential. The understanding and control of on-site p-wave interactions provides a necessary component for the assembly of multi-orbital lattice models, and a starting point for investigations of how to protect such a system from three-body recombination even in the presence of tunnelling.