Quantum fluids and solids articles from across Nature Portfolio

Layer-stacking domain walls in van der Waals heterostructures form a broadly tunable Luttinger liquid system, including both isolated and coupled arrays.

More than 40 years after the discovery of the quantum Hall effect, the investigation of new variants of this phenomenon and of the exotic physics they represent is still a lively research topic. In this Viewpoint, five scientists involved in the very recent discovery of a new type of Hall effect — the fractional quantum anomalous Hall effect — discuss their results and their implications.

IXPE has revealed how the spin of the accreting neutron star Hercules X-1 changes in three dimensions. The spin axis of the star moves both through the star and across the sky, hinting that the crust of the star is asymmetric by almost one part in a million.

Superfluidity, a liquid exhibiting frictionless flow, is so far limited to observations in low-temperature 3He and 4He, where the underlying mechanisms governing the quantum state are complex and different for each isotope, making for a fascinating but challenging phenomenon to study experimentally. The authors use isotope-sensitive neutron reflectometry to investigate mixed 3He/4He superfluid He films on a Si surface, and resolve the structural features and phase transitions that occur with changing temperature.

Metastable states found in superconductors and charge density wave materials are of fundamental interest. Vodeb et al. study the domain wall dynamics in 1T-TaS₂ using scanning tunneling microscopy and a quantum annealer, finding that in both cases the dynamics is driven by spectrally similar noise.

Scanning tunnelling microscopy of doped RuCl₃ shows distinct charge orderings at the lower and upper Hubbard bands, which can be attributed to a correlation-driven honeycomb hole crystal composed of hole-rich Ru sites and a rotational-symmetry-breaking paired electron crystal composed of electron-rich Ru–Ru bonds.

A superfluid is a macroscopic system with zero viscosity through which entropy is reversibly transported by waves. An unexpected transport phenomenon has now been observed between two superfluids, where irreversible entropy transport is enhanced by superfluidity.

90 years after Eugene Wigner predicted the formation of an ordered electron state, direct observations of a lattice of electrons in bilayer graphene not only verify the existence of a Wigner crystal but find unexpected physics.

Phonons do not carry spin or charge, but they can couple to an external magnetic field and cause a sizable transverse thermal gradient. Experiments suggest that phonon handedness is a widespread effect in magnetic insulators with impurities.

Graphene multistacks with four or five layers show the signature of correlated electronic states both in and out of a magnetic field.

Neutron spectroscopy, entanglement analysis, and simulations provide evidence that KYbSe₂ closely approximates a 2D quantum spin liquid. Although KYbSe₂ displays magnetic ordering at low temperatures, its magnetic dynamics are dominated by fractionalized excitations that exhibit anomalously large quantum entanglement, indicating that on finite timescales KYbSe₂ exhibits quantum spin liquid physics.

Recent experiments demonstrate ultrafast-fluid-like propagation of excitons in monolayers of MoS₂.