Physical Review B

Altermagnets can host superconducting states whose spin-up and spin-down condensates have different spatial pairing patterns. Here, the authors provide a comprehensive catalogue of allowed pairing states and explore their stability and topology. They predict a fractional ac Josephson effect for only one spin polarization in junctions between altermagnetic superconductors.

This work establishes necessary conditions for the exact dimer ground states in a wide class of spin chain models with arbitrary long-range interactions. The stability of the dimer phase is also probed by introducing an anisotropy or dimerisation with the analytical findings supported by the numerical computations. The considered models encompass physical phenomena ranging from spin-Peierls materials to dimer state implementations in quantum information processing.

In a Fermi liquid, the quasiparticle scattering rate scales as $T^2$, whereas the low-temperature correction to the residual resistivity can scale as $T^4$, seemingly implying a strongly suppressed current-relaxation rate. The authors resolve this paradox here by solving the kinetic equation exactly for a disordered, non-Galilean-invariant Fermi liquid. They show that electron–electron collisions enter the conductivity through the quasiparticle scattering time itself, which controls the crossover between collisionless and hydrodynamic transport. The extra $T^2$ factor arises because momentum conservation makes the change in the total velocity of two colliding electrons vanish on the Fermi surface, so current relaxation comes only from thermally excited states away from it. The electron–electron contribution to the dc conductivity nevertheless remains parametrically small throughout the Fermi-liquid regime. By extrapolating the result toward a $z=3$ quantum critical point, the authors further show that the renormalized quasiparticle scattering rate saturates the Planckian bound.

The self-energy is notoriously difficult to compute, especially in many-body systems with a discrete spectrum, where the Dyson equation often produces noncausal results. Here, the authors obtain a discrete spectral representation of the self-energy that is causal by construction, preserves sum rules, and requires no artificial broadening. Tested with four different impurity solvers, the approach significantly improves accuracy and enables a fully discrete formulation of dynamical mean-field theory.

Supersolidity, the coexistence of superfluidity and crystalline order, typically requires carefully tuned interactions. Here, the authors propose an alternative route: coupling a superfluid to phonons at a smooth solid interface. They show that this coupling can spontaneously induce a periodic density modulation while preserving superfluidity. The mechanism applies to both superfluid helium and Bose-Einstein condensates, and offers a route to engineering hybrid systems combining interfacial supersolidity with bulk superfluidity.

Here, the authors show that compression drives an anomalous metal–semiconductor–metal transition in the electride Ca${}_2$N. Initial compression localizes the extended interstitial anionic electrons, opening a band gap. Further compression induces rehybridization between the localized interstitial states and Ca d orbitals, restoring metallicity. These findings provide a unified framework linking interstitial electron behavior to electronic phase transitions in electrides.

Quantum spin liquids can preserve exactly the same symmetries while harboring fundamentally different patterns of fractionalization. Here, the authors uncover a landscape of gapped and gapless $U(1)$ and ℤ${}_2$ spin liquids on the ruby lattice, a frustrated geometry realized in programmable Rydberg atom arrays. Distinctive fingerprints in their excitation spectra and spin correlations offer a practical route to telling these elusive states apart in numerical studies and experiments.

Here, the authors combine resonant ultrasound spectroscopy (RUS), thermal and dielectric measurements, and strain analysis to reveal a rich sequence of ferroelastic and isosymmetric structural instabilities associated with octahedral tilting and the orientational ordering and dynamics of FA${}^{+}$ cations in formamidinium lead bromide (FAPbBr${}_3$). Acoustic loss reveals mobile ferroelastic domain walls and their sensitivity to thermal history, while the possibility of local polarity within these walls remains an open question.

The authors propose here a route to the superconducting diode effect through nonreciprocal magnetic domain-wall dynamics in ferromagnetic superconductors. Applied magnetic fields break time-reversal and inversion symmetries, producing direction-dependent critical currents for Walker breakdown—the onset of sustained domain-wall precession. Owing to the order parameter redundancy, the precession generates nonsingular phase slips. By connecting magnetic dynamics with superconducting transport, the authors identify a mechanism for realizing the superconducting diode effect without the need for complex heterostructures.

The authors study here the field-reentrant superconducting phase of the unconventional superconductor UTe${}_2$ using ultrasound measurements up to 77 T and down to 0.5 K. They find clear signatures of the field reentrant superconducting phase found for a field angle of 30 degrees from the $b$ to the $c$ axis in a longitudinal elastic mode, establishing the bulk nature of this superconducting phase. The authors observe an intriguing excess attenuation across the superconducting phase, which suggests unusual vortex dynamics and pinning mechanisms.

Altermagnetism arises from the breaking of time-reversal symmetry in antiferromagnets, leading to spin-band splitting. However, recent reports indicate inconsistencies in its observation in strongly correlated materials. Here, the authors employ dynamical mean-field theory to show that strong correlations in MnF${}_2$ suppress spin-band splitting, whereas MnTe exhibits significant spin-band splitting due to both strong correlations and sizable ligand hybridization, establishing it as an ideal altermagnetic candidate. These findings provide a pathway for designing altermagnets in strongly correlated systems.

Spin defects are promising building blocks for quantum technologies, but predicting how atomic vibrations reshape their electronic spectra remains challenging. Here, the authors employ a first-principles cumulant Green’s function approach that captures repeated phonon emission and absorption. For the negatively charged nitrogen-vacancy center in diamond, quantum zero-point motion produces multiphonon satellites spanning 400 meV even at zero temperature. The satellite energies and intensities depend strongly on spin and orbital character, revealing how individual defect states interact with the surrounding lattice.

The author predicts here the spin thermal Hall effect in nonreciprocal photonic many-body systems, where radiative heat transport generates a transverse accumulation of photon spin angular momentum. This effect and its inverse are shown to form an Onsager–Casimir reciprocal pair, establishing a fundamental connection between heat and photon-spin transport. Thermodynamic constraints further reveal universal bounds on spin–heat conversion and introduce a figure of merit for its efficiency, opening new perspectives for spin-controlled thermal radiation and photonic thermal devices.

Aperiodic tilings lie between crystalline order and disorder, giving rise to unusual wave phenomena. Here, the authors investigate 2D wave transport in the recently discovered Hat monotile based on exciton-polariton lattices, revealing localized, critical, and extended states within its fractal spectrum. Simulations reveal anomalous wave spreading, ranging from superdiffusive to near-subdiffusive transport. The authors propose an optical pump-probe approach to explore these effects experimentally, opening new avenues for studying critical phenomena in reconfigurable polariton lattices.

Here, the authors investigate electrical transport in twisted double bilayer graphene (TDBG) on the antiferromagnetic material CrOCl (COC). At ultrahigh magnetic fields, an enhanced correlated insulating state is observed at half-filling of TDBG, which is attributed to the charge transfer effect between TDBG and COC. The authors further characterize the behavior of the correlated state by systematic temperature- and magnetic-field dependent measurements. Their results highlight the interfacial charge-related effect as a promising approach to manipulating the correlated states in moiré systems.

Here, the authors substantially update the high-field magnetic phase diagram of SrFeO${}_3$, which hosts a hedgehog–antihedgehog lattice. Most strikingly, they uncover a first-order metamagnetic transition into the forced ferromagnetic phase, accompanied by negative volume magnetostriction and dramatic elastic softening. These anomalous magnetoelastic responses signal changes in charge degrees of freedom, shedding new light on the role of ligand holes in helical magnetism.

Realizing scalable Kitaev chains requires precise control over superconducting phases, to remove unwanted domain walls from the system. Here, the authors investigate two new control mechanisms for this purpose: tuning the spin state of the quantum dots and adjusting the charge of the Andreev bound state. Both approaches enable phase control without external magnetic flux, offering a potential route toward scalable architectures. The authors study spatially varying spin-orbit coupling as a potential cause of deviations from ideal $\pi$ phase shifts, revealing important challenges for future device design.

Here, the authors demonstrate that an applied direct electric field lifts the symmetry constraint on the nonlinear anomalous Nernst effect, enabling this effect in time-reversal symmetric 2D systems with crystallographic symmetries beyond a single mirror symmetry. They propose an alternating temperature gradient, rather than a steady one, as a driving force, allowing experimental detection via second-harmonic measurements. This finding broadens the material platform for quantum-geometry-induced transverse thermoelectric effects and provides an alternative route for thermoelectric energy harvesting.