###### EDITORS' SUGGESTION

The compound MnSb${}_{2}$Te${}_{4}$ is a close relative of the intrinsic antiferromagnetic topological insulator MnBi${}_{2}$Te${}_{4}$. Density functional theory predicts that a Weyl semimetal phase exists in ferromagnetic MnBi${}_{2}$Te${}_{4}$. Here, the authors fill in gaps in the magnetic imaging of MnSb${}_{2}$Te${}_{4}$ and confirm long-range ferromagnetic order in single crystals of ferromagnetic MnSb${}_{2}$Te${}_{4}$ using cryogenic magnetic force microscopy. The direct evidence of ferromagnetism in MnSb${}_{2}$Te${}_{4}$ paves the way for realizing the ferromagnetic Weyl semimetal phase in the family of Mn(Bi, Sb)${}_{2}$Te${}_{4}$.

Wenbo Ge *et al.*

Phys. Rev. B **103**, 134403 (2021)

###### EDITORS' SUGGESTION

No material perfectly realizes the frustrated quantum ferro-antiferromagnetic Heisenberg model on a square lattice, but BaCdVO(PO${}_{4}$)${}_{2}$ comes close. Here, the authors perform neutron spectroscopy measurements in high magnetic fields to determine an appropriate spin Hamiltonian for this system. They overcome numerous technical difficulties, such as the required ${}^{114}$Cd enrichment for neutron experiments and the complex sample mosaic. The results will help understand the previously discovered presaturation phase in this compound. Could it be the elusive spin nematic state?

V. K. Bhartiya *et al.*

Phys. Rev. B **103**, 144402 (2021)

###### EDITORS' SUGGESTION

Cuprate high-temperature superconductors universally exhibit a phase of charge order and a mysterious pseudogap phase. Using thermopower measurements, the authors explore here how the cuprate La${}_{1.6-x}$Nd${}_{0.4}$Sr${}_{x}$CuO${}_{4}$ (Nd-LSCO) evolves across these phases. They find that the thermopower displays a large increase below the pseudogap critical doping point ${p}^{*}$ and becomes negative in the charge order phase below that critical doping point ${p}_{\text{CDW}}$. This evolution hints at profound changes in the electronic structure at ${p}^{*}$ and ${p}_{\text{CDW}}$. They observe that these two critical dopings are well separated, implying that the two phases are clearly distinct.

C. Collignon *et al.*

Phys. Rev. B **103**, 155102 (2021)

###### EDITORS' SUGGESTION

Topological phases represent a pillar of modern condensed matter physics. While gapped topological systems have been studied extensively, gapless topological materials represent an exciting, largely unexplored area. Here, the authors show that symmetry can enrich random quantum critical points and phases. They uncover a class of gapless topological phases, protected by symmetry and robust to strong randomness. Some of these phases can be realized in nonequilibrium states stabilized by many-body localization. They also appear naturally in periodically driven (Floquet) systems.

Carlos M. Duque *et al.*

Phys. Rev. B **103**, L100207 (2021)

###### EDITORS' SUGGESTION

Superconductors absorb light despite having infinite dc conductivity. In a topologically trivial superconductor, such absorption is typically facilitated by disorder, giving rise to the anomalous skin effect. Here, the authors demonstrate that topology can mediate a new mechanism of optical absorption, dubbed the “topological anomalous skin effect”. In clean topological superconductors, the presence of surface states allow surface-to-bulk optical transitions. Specifically, for Weyl superconductors, the authors predict a characteristic absorption peak, which also survives in the presence of weak disorder.

Tsz Chun Wu, Hridis K. Pal, and Matthew S. Foster

Phys. Rev. B **103**, 104517 (2021)

###### EDITORS' SUGGESTION

Superfluid ${}^{4}$He, a strongly correlated Bose-Einstein condensed many-body system, displays sharp phonon-roton quantized excitations. Here, the authors report a complete determination of the dispersion relation of these excitations, using the most advanced inelastic neutron scattering methods as well as detailed dynamic many-body theory calculations. From the measured dispersion, the authors obtain, analytically as well as numerically, accurate tables of the thermodynamic properties. These highly precise results provide indispensable reference for a large variety of fundamental experimental and theoretical studies.

H. Godfrin *et al.*

Phys. Rev. B **103**, 104516 (2021)

###### EDITORS' SUGGESTION

Random quantum dynamics generates quantum error correcting codes that are robust against observers and errors. Here, the authors describe a simple physical picture of such codes, mapping characteristic code properties to the statistical mechanics of fluctuating “entanglement domain walls”. The error correcting criterion is understood as a decoupling condition of domain walls, which leads to a universal scaling law of the “code distance”.

Yaodong Li and Matthew P. A. Fisher

Phys. Rev. B **103**, 104306 (2021)

###### EDITORS' SUGGESTION

The connection of novel electromagnetic responses to Weyl nodes in topological semimetals is intriguing but difficult to establish in experiments. Here, the authors discover CeAlSi to be a new ferromagnetic Weyl semimetal by combining first-principles calculations with various experimental techniques. These reveal a new loop Hall effect that is induced purely by the proximity of the material’s Fermi level to its Weyl nodes. The loop Hall effect can potentially result from topological Fermi arcs located on magnetic domain walls.

Hung-Yu Yang *et al.*

Phys. Rev. B **103**, 115143 (2021)

###### EDITORS' SUGGESTION

Simulating nuclear quantum dynamics in strongly anharmonic materials is an open challenge where state-of-the-art techniques fail. This is relevant in ferroelectrics, charge density waves, and crystals encapsulating light atoms, such as superconductive high-pressure hydrides. Here, the authors develop a theory to compute dynamical properties and predict experimental Raman and IR spectroscopy, neutron scattering, and x-ray scattering of any material, accounting for the nuclear quantum and anharmonic dynamics.The method is efficient and can be applied to systems with hundreds of atoms even when treating electrons $a\phantom{\rule{0}{0ex}}b$ $i\phantom{\rule{0}{0ex}}n\phantom{\rule{0}{0ex}}i\phantom{\rule{0}{0ex}}t\phantom{\rule{0}{0ex}}i\phantom{\rule{0}{0ex}}o$ within density functional theory.

Lorenzo Monacelli and Francesco Mauri

Phys. Rev. B **103**, 104305 (2021)

###### EDITORS' SUGGESTION

Lattice gauge theories describe strongly interacting quantum many-body systems whose nonequilibrium properties in more than one dimension provide a challenge to current numerical methods. Here, the authors study a dimer model as an example of a U(1) gauge theory whose universal transport properties can be extracted using classically simulable methods. This is achieved by exploiting a surprising connection to topological solitons, enabling a venue of analysis that demonstrates how gauge constraints induce fractonic mobility, slow subdiffusive transport, and nonergodic dynamics.

Johannes Feldmeier, Frank Pollmann, and Michael Knap

Phys. Rev. B **103**, 094303 (2021)