Search

The spin–orbit interaction and the two-dimensional honeycomb structure of iridium-based oxides are promising for exotic electronic states. Here, the authors find an iridium oxide with a three-dimensional structure that preserves the features of the honeycomb systems, creating new material possibilities.

Unlike metals, Weyl and Dirac semimetals possess open discontinuous Fermi surfaces. Here, Potter et al.show how such materials may still exhibit characteristic electronic oscillations under applied magnetic fields via bulk tunnelling between Fermi arcs and predict their experimental signatures.

Quantum coherence should be rapidly lost in a system of many strongly coupled particles. Here, the authors show that this need not be the case in a one-dimensional magnet with impurities, allowing for a sharply defined topological phase even at high temperatures.

An algorithm based on symmetry indicators is used to search a crystallographic database and finds thousands of candidate topological materials, which could be exploited in next-generation electronic devices.

A crystal is a band insulator if the energy bands are filled with electrons. Partially filled bands result in a metal, or sometimes a Mott insulator when interactions are strong. A study now shows that for many crystalline structures, the Mott insulator is the only possible insulating state, even for filled bands.

Topological insulators are band insulators in which spin–orbit coupling takes the role of the applied magnetic field in the integer quantum Hall effect. Theory now predicts that dislocations in such systems can give rise to one-dimensional topologically protected states, resembling helical modes at the edge of a two-dimensional quantum spin Hall insulator.

Qudits can encode a richer class of topologically ordered states, which are promising for quantum information, but experimental realizations have been limited to qubits. Here, the authors report a study of a qutrit toric code on a trapped-ion quantum computer.

Integrating mirrors with magnetic components is crucial for constructing chiral optical cavities, which provide tunable platforms for time-reversal-asymmetric light-matter interactions. Here, the authors introduce single-crystal circular-polarization-selective mirrors based on chiral superconductors, which break time-reversal symmetry themselves, eliminating the need for additional components.

The dynamical axion quasiparticle, which is directly analogous to the hypothetical fundamental axion particle, is observed in two-dimensional MnBi₂Te₄, and has implications for quantum chromodynamics, cosmology and string theory.

Measurements of the superfluid stiffness in twisted trilayer graphene reveal unconventional nodal-gap superconductivity, where the superconducting transition is controlled by phase fluctuations rather than Cooper-pair breaking.

Measurements combined with post-processing of their outcomes can be used to prepare ordered quantum states. It has been shown that they can drive a Nishimori phase transition into a disordered state even in the presence of quantum errors.

Three-dimensional Dirac semimetals such as Cd₃As₂ are attracting attention because their electronic structure can be considered to be the three-dimensional analogue of graphene’s. Low-temperature scanning tunnelling measurements of the 112 cleavage plane of Cd₃As₂ now reveal its electronic structure down to atomic length scales, as well as its Landau spectrum and quasiparticle interference pattern.

The authors demonstrate control of antiferromagnetic order using helical light.

A trapped-ion quantum processor is used to create ground-states and excitations of non-Abelian topological order on a kagome lattice of 27 qubits with high fidelity.

Twisted double bilayer graphene hosts flat bands that can be tuned with an electric field. Here, by using gate-tuned scanning tunneling spectroscopy, the authors demonstrate the tunability of the flat band and reveal spectral signatures of correlated electron states and the topological nature of the flat band.

Electromagnetic response of topological materials is described the so called axion electrodynamics which contains additional relations between the fields. Here the authors extend the theory of axion electrodynamics to general optical frequencies and apply it to a realistic topological antiferromagnet.

In conventional materials, charge carriers are electron-like quasiparticles, but topological bands allow for more exotic possibilities. Here, the authors predict that in the Chern-ferromagnet phase of twisted bilayer graphene charge is carried by spin polarons, bound states of an electron and a spin flip.

The authors demonstrate a spectroscopic method, based on magnetotransport measurements, to quantitatively measure the size of the correlated gaps in twisted trilayer graphene and infer their topology.

The modern understanding of quantum transport relies on geometric concepts such as the Berry phase. The geometric approach has now been extended to the theory of optical transitions.

A study using local compressibility measurements reports fractional Chern insulator states at low magnetic field in magic-angle twisted bilayer graphene, and establishes the applied magnetic field as a means to tune the Berry curvature distribution.

Twisted double bilayer graphene devices show tunable spin-polarized correlated states that are sensitive to electric and magnetic fields, providing further insights into correlated states in two-dimensional moiré materials.

Symmetry labels of materials under certain space groups can be used to indicate their band topology. Integrating that into first-principles band-structure calculations, new topological materials with a diversity of topological phenomena are discovered.

Twisted bilayer graphene exhibits correlated electronic phases and superconductivity, but its precise nature is under debate. Here, Lee and Khalaf et al. study a twisted double bilayer graphene, where ferromagnetic insulator and spin triplet superconducting phases can be stabilized.

The class of quantum phases with symmetry-protected topological properties can be generalized in the concept of symmetry-protected topological phases. Here, Chen and colleagues present an intuitive way of constructing a large class of those phases in different dimensions.

Electron filling criterion can guide the search for new topological materials with nodal-point or nodal-line Fermi surfaces.

Lattice gauge theories are notoriously hard to analyse at finite fermion density, due to the so-called fermion sign problem. A study now shows this can be circumvented for the case of Ising gauge theories.

The Dirac spin liquid is a candidate description for the strongly correlated behaviour of some quantum magnets. Song et al. study the symmetry dependence physics of monopole excitations and argue that the lattice-dependent consequences for magnetic ordering may provide a unifying picture for 2D quantum magnetism.

Understanding the role of topology in determining electronic structure can lead to the discovery, or appreciation, of materials with exotic properties such as protected surface states. Here, the authors present a framework for identifying topologically distinct band-structures for all 3D space groups.

Electronic transport measurements in a magnetic field on the topological Dirac semimetal Cd₃As₂ identify the predicted Weyl orbits that weave Fermi arcs and bulk states together; the Weyl orbits enable transfer of chirality from one node to another, and open up the possibility of controlling topological properties electronically.

In addition to the broken time-reversal symmetry that typifies Chern insulators, twisted bilayer graphene hosts a set of topological states with broken translational symmetry.

Topological quantum states are essential resources in quantum error correction and quantum simulation but unitary quantum circuits for their preparation require extensive circuit depth. The authors demonstrate a constant-depth protocol to prepare topologically ordered states on a trapped-ion quantum computer using non-unitary operations.