Search

Despite decades of intense theoretical, experimental and computational effort, a microscopic theory of high-temperature superconductivity is not yet established. Eight researchers share their contributions to the search for a better understanding of unconventional superconductivity and their hopes for the future of the field.

The Higgs mechanism is best known for generating mass for subatomic particles. Less well-known is that the idea originated in the study of superconductivity, and can be tested in the laboratory.

After decades of research, the microscopic details of the superconductor–insulator transition in two-dimensions, which is driven by the presence of disorder, are revealed by simulations. These include a phase transition from a gapped superconductor to a gapped insulator, for example.

The authors study the formation and characteristics of a Majorana metallic quantum spin liquid state in Kitaev’s honeycomb model under a moderate external magnetic field. This state represents a novel class of gapless quantum spin liquids stabilized by magnetic field.

It is well known that flat bands exist in magic-angle twisted bilayer graphene. Now thermopower measurements show that the strong correlations between electrons in these bands result in the formation of local moments.

The electron is responsible for charge and spin transport in conventional metals. In contrast, the existence of well-defined electronic excitations in the metallic state of high-temperature superconductors is highly debated.

Recognizing a superfluid when we see one may be more difficult than we originally thought. Simulations suggest that the sharp peaks associated with superfluidity in ultracold atoms do not provide a unique signature after all.

Why are the superconducting pairs in high-temperature superconductors so resilient to the presence of disorder? The strong electronic correlations appear to be the answer.

MoTe₂ is reported to host type II topological Weyl semimetal states. Two sets of Weyl points exist at different energies above the Fermi energy. Fermi arcs that form closed loops and are unique to type II Weyl semimetals are also found.

Thin samples CrI₃ exhibit a phase transition under an applied magnetic field from layered antiferromagnetism to ferromagnetism. Here the authors observe an associated abrupt change in the magneto-Raman spectra, illustrating the sensitivity of Raman spectra to magnetic ordering.

Superconductivity has been discovered in atomically thin two-dimensional van der Waals materials by resistance measurements, but magnetic measurements are lacking. Here, the authors use a micron-scale SQUID magnetometer to measure the superfluid response of exfoliated MoS₂.

A thermal signature of the chiral anomaly is reported in an ideal Weyl semimetal.

Ultracold atomic gases in optical lattices potentially offer simulations of condensed-matter phenomena beyond what theory and computations can access; compensated optical lattice techniques applied to the Hubbard model now enable unprecedented low temperatures to be reached for fermions — only 1.4 times that of the antiferromagnetic phase transition, approaching the limits of present modelling techniques.

Characterizing quantum phases realized in simulation can be difficult, such as the re-entrant gapless phase of the Kitaev model induced by a magnetic field. Employing a quantum-classical hybrid approach that involves mining projective snapshots with interpretable classical machine learning, the authors uncovered Friedel oscillations of a spinon Fermi surface, providing support for a gapless quantum spin liquid.