Topological semimetals offer a rich platform for exploring massless fermion physics and realizing exotic properties with potential technological applications. GdPS, a magnetic semiconductor derived from the nodal-line semimetal ZrSiS family, exhibits a field-induced insulator-to-metal transition driven by exchange splitting. This transition is accompanied by an unusual, isotropic, and gigantic negative magnetoresistance, attributed to negligible magnetic anisotropy resulting from the weak spin-orbit coupling of half-filled Gd3+ 4f orbitals and light S atoms. In this work, we investigate Se substitution, which is expected to enhance spin-orbit coupling. Indeed, we observe slightly increased magnetic anisotropy in magnetotransport. Moreover, Se substitution suppresses the field-induced insulator-to-metal transition, likely due to an enlarged band gap that demands a higher exchange splitting to close. These findings provide deeper insights into the interplay between spin-orbit coupling, magnetic anisotropy, and transport behavior in GdPS, offering guidance for future materials design for desired functionalities.

The MnP family of binary compounds presents an intriguingly simple platform to mix-and-match elemental components. Replacement on the transition metal or pnictogen site can alter magnetism, electronic correlations, and electrical properties. Here we report low-temperature properties of CoP, including measurements at magnetic fields exceeding 30 T, revealing de Haas-van Alphen oscillations and a nearly two orders of magnitude increase in resistance. When viewed together with prior work, it is possible to put together a global picture of the role of different atoms in variations in magnetic ordering, lattice coherence, and topological band structure features in this material family.

Magnetic topological insulators provide a unique platform to explore the interplay between magnetism and topology. MnBi2Te4, known for its A-type antiferromagnetic (AFM) ground state, undergoes a striking transformation when single crystals are grown in an applied magnetic field. Despite retaining the same crystal structure, field-grown MnBi2Te4 exhibits a ferromagnetic (FM) ground state with a Curie temperature of ~12.5 K, confirmed by magnetization, magnetic torque, electrical resistivity, and specific heat measurements. First-principles calculations support these findings, revealing that magnetic-field-assisted synthesis can effectively reconfigure the ground-state spin order and thereby modify the material’s electronic properties, as reflected in the de Haas-van Alphen oscillation seen in the magnetic torque. Magnetic topological insulators offer a promising avenue to study the interaction between magnetism and topology. Here, the authors demonstrate that MnBi₂Te₄, typically an antiferromagnet, develops a ferromagnetic ground state despite retaining the same crystal structure when synthesized in a magnetic field, highlighting the potential of magnetic-field-assisted synthesis in designing materials with tunable electronic properties.

We report a ferromagnetic-like anomalous Hall resistivity and giant isotropic negative magnetoresistance (NMR) in the antiferromagnetic half-Heusler compound DyPdBi. The FM-like anomalous Hall resistivity appears exclusively in antiferromagnetic state II, yet it is not coupled to magnetization, indicating a Berrycurvature origin. Additionally, the magnetoresistance drops by 98%, and the NMR persists above the N & eacute;el temperature (TN). We attribute both phenomena to a half-topological-semimetal (HTS) state, similar to that proposed for TbPdBi, arising from weak band inversion strength (BIS). This state enhances spin polarization, reducing Berry curvature cancellation and strengthening anomalous Hall effect (AHE). These observations suggest that weak BIS in the RPdBi family gives rise to an HTS that potentially interacts with exotic spin states, producing an exceptionally large AHE. This study highlights a strategy for engineering large AHE in half-Heusler antiferromagnets, and advances the further topological spintronics design.

Magnetic impurities provide a route toward increasing functionality in electronic materials, often enabling new device concepts and architectures. In the case of topological semimetals, dilute magnetic doping presents a particularly attractive approach for inducing a Dirac to Weyl phase change via time reversal symmetry breaking. However, efforts to realize changes in the electronic structure have been limited by challenges in incorporating magnetic impurities into crystals with sufficiently high electron mobilities to detect them via transport or spectroscopic techniques. Here, we demonstrate incorporation of Mn into Dirac semimetal thin films grown by molecular beam epitaxy (MBE). Using As-rich growth conditions and [001] oriented thin films, Mn compositions of 10% are achieved. Films contain uniform distributions of Mn with no evidence of secondary phases and exhibit electron mobilities greater than 10 000-30 000 up to 5% Mn. An evolution in the magnetization behavior along with the emergence of a second quantum oscillation frequency at low Mn concentrations provide preliminary evidence of Mn-induced changes in the electronic structure that are consistent with a Weyl phase. This work demonstrates the potential of magnetically doping topological semimetal thin films and a pathway for synthesizing them.

Low carrier densities in semimetals enable the exploration of magnetotransport in the quantum limit. Recent findings consistent with 3D quasi-quantum Hall effect (QQHE) have positioned semimetals as promising platforms for exploring 3D quantum Hall-like transport, but the lack of tunability in the Fermi level has limited QQHE observation. Here, we show how achieving ultralow carrier densities in the Dirac semimetal Cd3As2 ( ~ 1016 cm−3) can reveal QQHE signals at modest fields. At these low densities where QQHE is most accessible, we find that clear QQHE is obscured by charged disorder, which broadens Landau bands, scatters carriers, and affects quasi-quantization. Clear observation of QQHE in semimetals depends on Fermi level and disorder potential magnitudes. As theoretically predicted, Coulomb disorder is an essential ingredient for understanding the magnetoresistivity for a spectrum of Fermi levels in Cd3As2, anchoring the role of charged disorder in topological semimetal applications. We discuss future constraints and opportunities in exploring 3D QQHE in semimetals. Semimetals offer a promising platform for exploring 3D quantum Hall-like transport, but the lack of tunability in the Fermi level has hindered the observation of quasi-quantum Hall effects (QQHE). Here, the authors achieve ultralow carrier densities in Cd3As2, revealing QQHE signals at modest fields, while highlighting the critical role of charged disorder in affecting quasi-quantization, with implications for topological semimetal applications.

Magnetic fields typically suppress superconductivity through Pauli and orbital limiting effects. However, there are rare instances of magnetic-field-induced superconductivity, as observed in Chevrel-phase compounds, organic conductors, uranium-based heavy-fermion systems, and moiré graphene-although these materials possess inherently low superconducting transition temperatures (Tc). Here, we demonstrate high-field-stabilized superconductivity in a class of materials recently shown to have significantly higher Tc values (up to 40 K): the infinite-layer nickelates. We show that both the low-field and high-field superconducting states can be understood in terms of a field-compensation mechanism, better known as the Jaccarino-Peter effect. These findings demonstrate the possibility of achieving substantially enhanced upper critical fields in high-temperature superconductors.

In our recent study of the high magnetic field phase landscape of UTe_2 [Phys. Rev. X 15, 021019 (2025)] we found indirect evidence that the SC3 superconducting phase spills out beyond the first-order phase boundary of the spin-polarized state. This prior study was limited to a maximal field strength of 41.5 T, and mapped the b-ac rotation plane. Here we measure a high quality sample with residual resistivity ratio RRR = 605 under rotations in the b-c plane up to 45 T. This extended field range helps to unambiguously demonstrate the spillover of SC3 outside the polarized paramagnetic state. This is identified by the observation of zero resistance at low temperatures, for magnetic field strengths lower than the metamagnetic transition field resolved at higher temperatures. This observation is consistent with the scenario that electronic pairing of the SC3 phase is mediated by quantum critical fluctuations.

We present a detailed study of magnetization, resistivity, heat capacity, and x-ray and neutron powder diffraction measurements performed on single crystals of nonstoichiometric CeAuBi2, Au deficiency 18%, a strongly correlated antiferromagnet with N & eacute;el temperature TN = 13.2 K. Field-dependent magnetization measurements reveal a large magnetic anisotropy at low temperatures with an easy axis along the crystallographic c axis, in which direction a spin-flop transition exhibits strong features in magnetization, specific heat, and resistivity at Hc = 75 kOe. The constructed temperature-field phase diagram connects this transition to the suppression of magnetic order, which evolves from a second-order nature into a first-order transition that bifurcates at the spin-flop transition into three transitions below 1 K. The smoothed nature of the metamagnetic transitions in nonstoichiometric CeAuBi2 is well described by an Ising model with weak quenched disorder, suggesting that the presence of Au vacancies is sufficient to smear the complex metamagnetic behavior and tune the critical behavior of magnetic order.

In the past decade, moiré materials have revolutionized how we engineer and control quantum phases of matter1,2. They are versatile platforms for strongly correlated electronic phenomena3,4 and support new ferroelectric5,6, magnetic7 and superconducting states8. Among incommensurate materials9, moiré materials are aperiodic composite crystals10,11 whose long-wavelength superlattices enable tunable properties without chemically modifying their layers. So far, nearly all reports of moiré materials have investigated van der Waals heterostructures assembled far from thermodynamic equilibrium (T < 150 °C)1,2. Here we introduce a conceptually new approach to synthesizing high-mobility moiré materials in thermodynamic equilibrium. We report a new family of foliated superlattice materials (Sr6TaS8)1+δ(TaS2)8 that are exfoliatable, incommensurate-lattice, van der Waals crystals. Lattice mismatches between alternating layers generate moiré superlattices, analogous to 2D moiré heterobilayer superlattices, which are coherent throughout these crystals and tunable through synthesis conditions without altering their chemical composition. Quantum oscillation measurements map the complex Fermiology of these moiré metals12-14, showing that the Fermi surface of the structurally simplest moiré metal comprises more than 40 distinct cross-sectional areas. This is naturally understood by proposing that these bulk moiré metals encode electronic properties of higher-dimensional superspace crystals in ways paralleling well-established crystallographic methods for incommensurate lattices15,16. More broadly, our work demonstrates a scalable synthesis approach potentially capable of producing large-area moiré materials for electronics applications and evidences a new material design concept for accessing phenomena proposed in higher dimensions17-21.

The Pauli limiting field imposed by the Zeeman effect bounds the upper critical field of weak-coupling superconductivity. It is determined by setting the condensation energy equal to the paramagnetic energy and scales inversely with the effective g-factor. Here, we demonstrate that in a few-layer-thick van der Waals superconductor, PdTe2, quantum confinement can tune the effective g-factor causing the Pauli limit to become thickness-dependent. We experimentally probe the in-plane upper critical field, Hc2∥, of PdTe2 at multiple intermediate thicknesses down to 20 mK. We find that Hc2∥ is enhanced by more than an order of magnitude as the thickness is reduced from 50 nm down to 17 nm. We model the temperature- and thickness-dependent Hc2||, revealing a thickness-dependent spin Zeeman depairing mechanism impacting its value. Our findings reveal how quantum confinement drives a reduction in g that enhances the Pauli limiting field and allows the measured enhancement of Hc2∥. A violation of the Pauli limit is often associated with unconventional pairing symmetry in superconductors. Our work demonstrates that this simple association is difficult without knowledge of the g-factor, particularly in layered materials.

Valleytronics is a rapidly advancing field that explores the use of the valley degree of freedom in electronic systems to encode and process information. It relies on electronic states with spin-valley locking, first predicted and observed in monolayer transition metal dichalcogenides like MoS2. However, very few bulk materials have been reported to host spin-valley locked electronic states. In this work, we present experimental evidence for a predicted, unique spin-valley locked electronic state generated by the Bi zig-zag chains in the layered compound BaMnBi2. We observed remarkable quantum transport properties in this material, including stacked quantum Hall effect (QHE) and nonlinear Hall effect (NLHE). From the analysis of the QHE, we identified a spin-valley degeneracy of 4, while the NLHE provides supporting evidence for the anticipated valley-contrasted Berry curvature-a typical signature of a spin-valley locked state. This spin-valley locked state contrasts with that observed in the sister compound BaMnSb2, where the degeneracy is 2. This difference arises from significant variations in their orthorhombic structures and spin-orbital coupling. These findings not only set up a new platform for exploring coupled spin-valley physics in bulk materials but also underscores its potential for valleytronic device applications.

Altermagnets, a class of collinear magnets defined by their spin-split electronic bands, are a focus of intense research, where a key challenge is to experimentally verify this unique band structure as a bulk property. Here, we report a comprehensive quantum oscillation study on the prototypical altermagnet CrSb. By combining high-field magnetotransport and torque measurements with DFT+U calculations including spin-orbit coupling, we successfully identify a multitude of quantum-oscillation frequencies originating from four spin-non-degenerate bands. These results provide definitive, bulk-sensitive evidence for the altermagnetic spin-split Fermi surface of CrSb, which provides a firm foundation for exploring its novel electronic properties.

Cooper pairing in most of the known fermionic superfluids occurs via spin-1/2 quasiparticle interactions that lead to spin-singlet or spin-triplet pairing. In the topological semimetal YPtBi, strong spin-orbit coupling results in a band inversion between highly symmetric s- and p-like electronic bands and a degeneracy at the Γ point that ensures the manifold of j=3/2 quasiparticle states thrive near the Fermi level, where superconducting pairing occurs. Here we study the effects of magnetic and nonmagnetic disorder and carrier density on this exotic superconducting pairing state. By varying levels of disorder and carrier densities by nearly two and three orders of magnitude, respectively, we show that the superconducting critical temperature of YPtBi has a remarkable robustness, with little variation across this span. Our results suggest that superconductivity in YPtBi may reside in a regime where phase stiffness, rather than pair formation, governs the transition temperature. The insensitivity of Cooper pairing to dramatic changes in quasiparticle environment in a j=3/2 superconductor highlights a new form of protection realized in topological high-spin superconductors.

Below a critical temperature T c , superconductors transport electrical charge without dissipative energy losses. The application of a magnetic field B generally acts to suppress T c , up to some critical field strength at which T c → 0 K. Here, we investigate magnetic field–induced superconductivity in high-quality specimens of the triplet superconductor candidate UTe 2 in pulsed magnetic fields up to B = 70 T. Strikingly, we find that this material has a higher T c when B > 40 T ( T c ≈ 2.4 K) than it does for B = 0 T ( T c = 2.1 K). This observation points to a fundamentally distinct mechanism for the formation of superconductivity at high B in UTe 2 compared to the case of B = 0 T.

Quantum critical phenomena are widely studied across various materials families, from high-temperature superconductors to magnetic insulators. They occur when a thermodynamic phase transition is suppressed to zero temperature as a function of some tuning parameter such as pressure or magnetic field. This generally yields a point of instability—a so-called quantum critical point—at which the phase transition is driven exclusively by quantum fluctuations. Here, we show that the heavy fermion metamagnet UTe_{2} possesses a quantum phase transition at extreme magnetic field strengths of over 70 T. Rather than terminating at one singular point, we find that the phase boundary is sensitive to magnetic field components in each of the three Cartesian axes of magnetic field space. This results in the transition surface being bounded by a continuous ring of quantum critical points, the locus of which forms an extended line of quantum criticality—a novel form of quantum critical phase boundary. Within this quantum critical line sits a magnetic field-induced superconducting state in a toroidal shape, which persists to fields over 70 T. We model our data by a phenomenological free energy expansion and show how a quantum critical line—rather than a more conventional singular point of instability—anchors the remarkable high magnetic field phase landscape of UTe_{2}.

This study investigates the electronic structure of the kagome metal YbTi3Bi4 using high-field torque magnetometry. The torque signal measured at a maximum field of 41.5 T reveals clear de Haas-van Alphen (dHvA) oscillations with a major frequency peak at F delta 130 T. By rotating the sample at various tilt angles 0, we observed that F delta exhibits a nearly 1/cos0 dependence, indicating the presence of a quasi-two-dimensional (2D) Fermi surface (FS) in YbTi3Bi4. This argument is further supported by the detection of a forward-leaning, sawtoothlike waveform in the dHvA effect, a hallmark of 2D FS characteristics. Notably, we identified two high-frequency peaks near F chi 1900 T and F lambda 5600 T; however, these peaks quickly disappear at 0 greater than 21 degrees. To better understand experimental observations, we computed the electronic band structure and FS using ab initio density-functional theory (DFT). The electronic bands reveal the presence of several Dirac points, flat bands, and van Hove singularities near the Fermi level. Five bands cross the Fermi level and contribute to the FS of this material. The FS comprises cylindrical sheets, with theoretical frequencies from the FS pockets aligning well with the experimental dHvA frequencies. Several FS parameters characterizing F delta were determined by analyzing the temperature and field dependence of the dHvA oscillations using the Lifshitz-Kosevich theory. The detailed electronic properties presented in this work provide critical insights into the electronic structure of YbTi3Bi4 and other titanium-based kagome compounds.

In magnetic pyrochlore materials, the interplay of spin-orbit coupling, electronic correlations, and geometrical frustration gives rise to exotic quantum phases, including topological semimetals and spin ice. While these phases have been observed in isolation, the interface-driven phenomena emerging from their interaction have never been realized previously. Here, we report on the discovery of interfacial electronic anisotropy and rotational symmetry breaking at a heterostructure consisting of the Weyl semimetal Eu2Ir2O7 and spin ice Dy2Ti2O7. Subjected to magnetic fields, we unveil a sixfold anisotropic transport response that is theoretically accounted by a Kondo-coupled heterointerface, where the spin ice's field-tuned magnetism induces electron scattering in the Weyl semimetal's topological Fermi-arc states. Furthermore, at elevated magnetic fields, we reveal a twofold anisotropic response indicative of the emergence of a symmetry-broken many-body state. This discovery showcases the potential of pyrochlore frustrated magnet/topological semimetal heterostructures in search of emergent interfacial phenomena.

To date, the most widely-studied quantum anomalous Hall insulator (QAHI) platform is achieved by dilute doping of magnetic ions into thin films of the alloyed tetradymite topological insulator (TI) (Bi$_{1-x}$Sb$_x$)$_2$Te$_3$ (BST). In these films, long-range magnetic ordering of the transition metal substituants opens an exchange gap $\Delta$ in the topological surface states, stabilizing spin-polarized, dissipationless edge channels with a nonzero Chern number $\mathcal{C}$. The long-range ordering of the spatially separated magnetic ions is itself mediated by electronic states in the host TI, leading to a sophisticated feedback between magnetic and electronic properties. Here we present a study of the electronic and magnetic response of a BST-based QAHI system to structural tuning via hydrostatic pressure. We identify a systematic closure of the topological gap under compressive strain accompanied by a simultaneous enhancement in the magnetic ordering strength. Combining these experimental results with first-principle calculations we identify structural deformation as a strong tuning parameter to traverse a rich topological phase space and modify magnetism in the magnetically doped BST system.