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We develop a theoretical framework for probing superconductivity with momentum resolution using the quantum twisting microscope (QTM), a planar tunneling device where a graphene tip is rotated relative to a two-dimensional sample. Because of in-plane momentum conservation, the QTM directly measures the superconducting spectral function along well-defined trajectories in momentum space. The relative intensities of electron and hole excitations encode the Bogoliubov coherence factors, revealing the momentum dependence of the pairing magnitude. Three C_{3z}-related tunneling channels enable direct detection of rotational symmetry breaking, as well as nodal points in the superconducting order parameter. We apply our framework to superconductivity within the Bistritzer-MacDonald model of noninteracting electrons and the topological heavy-fermion model, which accounts for electron-electron interactions. Together, these capabilities establish the QTM as a direct probe of the pairing symmetry and microscopic origin of superconductivity in two-dimensional materials.

Self-intercalation in transition metal dichalcogenides (TMDs) offers a unique strategy for doping and spin ordering that preserves structural integrity, minimizing lattice distortions. This modification introduces additional electron density, spin states, and potentially spontaneous superlattice formation. Combining with further high-pressure modulation, more quantum phenomena could be induced for new physics exploration. Here, we present a high-pressure study of the self-intercalated compound V_{1/4}VS_{2}, where antiferromagnetic order arises from 3d electrons localized on the vanadium atoms intercalated between the layers. Under pressure, these localized electrons progressively delocalize, leading to the suppression of the antiferromagnetic order and the emergence of non-Fermi liquid behavior near 9 GPa, signaling an antiferromagnetic quantum critical point. Under higher pressure, a Lifshitz transition-induced superconductivity is observed, while the crystalline symmetry remains preserved up to 104.4 GPa. Notably, this marks the first observation of superconductivity in a self-intercalated TMD under pressure. These findings highlight V_{1/4}VS_{2} as a model two-dimensional system for exploring pressure-induced quantum criticality, electronic topological transitions, and related nontrivial superconductivity, paving the way to new physics by fully exploring the potential of self-intercalated TMDs.

Under the deformation potential model, the superconducting phenomenon in ABC-stacked multilayer graphene under a vertical electric field is investigated using linear combination operators and unitary transformation methods. Through the deformation potential model applied to a linear continuous medium, the effect of the external electric field is converted into the deformation potential energy of the crystal. Deformation potential phonons (LA phonons) act as propagators, generating electron-electron interactions. As the electric field increases, the ratio of the electric displacement vector to the dielectric function (D/ε) rises, leading to an increase in the electron ground-state energy, the opening of the band gap, and an enhancement of the attractive electron-electron interaction. With further increases in the external electric field, the deformation potential constant of the crystal (Dl) increases. When the phonon vibration frequency (ω) is around 8.5 THz, and the conditions are satisfied-where the wave vectors of different LA phonons are equal in magnitude and opposite in direction, and the electron spins are opposite-the attractive electron-electron interaction reaches its maximum (Heff), resulting in the emergence of superconductivity. Our study also provides a new perspective for understanding the unique quantum properties-such as strong correlations, superconductivity, and ferromagnetism-in different stacking configurations like AB, ABC, and ABCA.

Using the Sierpiński gasket (triangle) and carpet (square) lattices as examples, we theoretically study the properties of fractal superconductors. For that, we focus on the phenomenon of s-wave superconductivity in the Hubbard model with attractive on-site potential and employ the Bogoliubovde Gennes approach and the theory of superfluid stiffness. For the case of the Sierpiński gasket, we demonstrate that fractal geometry of the underlying crystalline lattice can be strongly beneficial for superconductivity, not only leading to a considerable increase of the mean-field pairing temperature Tc as compared to the regular triangular lattice but also supporting macroscopic phase coherence of the Cooper pairs. In contrast, the Sierpiński carpet geometry does not lead to pronounced effects, and we find no substantial difference as compared with the regular square lattice. We conjecture that the qualitative difference between these cases is caused by different ramification properties of the fractals.

Topological quasiparticle excited states, magnetotransport, spin Hall effect, and superconductivity in solid-state materials have consistently been the four key issues in condensed matter physics. In this work, we theoretically demonstrate that monolayer In 2 O ${\rm In}_2{\rm O}$ provides an effective platform to explore these intertwined phenomena through its unique electronic topology. First-principles calculations reveal a type-II Dirac point near the Fermi level of the electronic band structure of monolayer In 2 O ${\rm In}_2{\rm O}$ , which is split into two pairs of Weyl points with topological charges of ± 1 $\pm 1$ in the presence of spin-orbit coupling. Robust edge states along the (100) direction confirm its topologically nontrivial nature. Remarkably, the system exhibits negative magnetoresistance below the temperature of 30 K with a significant Hall conductance and a predicted superconducting transition at 1.5 K, which are induced both by phonon softening and van Hove singularities. These theoretical findings establish the monolayer In 2 O ${\rm In}_2{\rm O}$ as a prototypical two-dimensional material for investigating type-II Dirac physics and the interplay of topological states, magnetotransport, and superconductivity.

UTe2 exhibits the remarkable phenomenon of re-entrant superconductivity, whereby the zero-resistance state reappears above 40 tesla after being suppressed with a field of around 10 tesla. One potential pairing mechanism, invoked in the related re-entrant superconductors UCoGe and URhGe, involves transverse fluctuations of a ferromagnetic order parameter. However, the requisite ferromagnetic order-present in both UCoGe and URhGe-is absent in UTe2, and neutron scattering shows instead that the magnetic susceptibility is peaked at an antiferromagnetic wavevector. Here, we measure the magnetotropic susceptibility of UTe2 across two field-angle planes. This quantity is sensitive to the magnetic susceptibility in a direction transverse to the applied magnetic field-a quantity that is not accessed in conventional magnetization measurements. We observe a very large decrease in the magnetotropic susceptibility over a broad range of field orientations, indicating a large increase in the transverse magnetic susceptibility. Because our technique probes the magnetic susceptibility in the long wavelength (q = 0) limit, this suggests that the strong transverse susceptibility arises from ferromagnetic spin fluctuations. These ferromagnetic fluctuations are likely important for understanding the pairing mechanism in UTe2, as all three superconducting phases of UTe2 surround this region of enhanced susceptibility in the field-angle phase diagram.

In low-dimensional superconductors, the interplay between quantum confinement and interfacial hybridization effects can reshape Cooper-pair wavefunctions and give rise to unconventional superconducting states. Here we use plasma-free confinement epitaxy assisted by a carbon buffer layer to synthesize a gallium trilayer sandwiched between graphene and a 6H-SiC(0001) substrate. Within this confined gallium layer, we demonstrate interfacial Ising-type superconductivity driven by atomic orbital hybridization. Electrical transport measurements reveal that the in-plane upper critical magnetic field reaches ~21.98 T at T = 400 mK, approximately 3.38 times the Pauli paramagnetic limit. Angle-resolved photoemission spectroscopy measurements, combined with theoretical calculations, confirm the presence of split Fermi surfaces with Ising-type spin textures at the K and K' valleys of the confined gallium layer, originating from strong hybridization with the SiC substrate. This work establishes a strategy for realizing unconventional pairing wavefunctions through the synergistic combination of quantum confinement and interfacial hybridization effects.

Strongly interacting fermions represent the key constituent of several intriguing phases of matter. However, due to the inherent complexity of these systems, important regimes are still inaccessible. Here, we derive a realistic and flexible setup based on ultracold magnetic lanthanide atoms trapped in a one-dimensional optical lattice. Leveraging their large magnetic moments, we design a fermionic t-J model with independently tunable hopping, spin-spin couplings, and onsite interaction. Through combined analytical and numerical analysis, we uncover a variety of many-body quantum phases-including superconducting and topological states. Crucially, in the regime of attractive onsite interaction, we reveal that topology and superconductivity coexist, thus giving rise to an exotic state of matter: a topological triplet superconductor. We also outline a practical protocol to prepare and detect all discovered phases using current experimental techniques. Our results establish an alternative and powerful route for a deeper understanding of strongly interacting fermionic quantum matter.

This study investigates the structural evolution and superconducting mechanisms of arsenic (As) under pressures ranging from 0 to 400 GPa using first-principles calculations. The phase transition sequence aligns with experimental data ( R 3 ¯ m - P m 3 ¯ m -HG phase- I m 3 ¯ m ), with the As phase demonstrating stability between 100 and 400 GPa. At 100 GPa, the As-IV ( I m 3 ¯ m ) phase exhibits a superconducting transition temperature (Tc) of 5.5 K, driven by As-p orbital hybridization, which enhances the density of states at the Fermi level and strengthens electron-phonon coupling. However, as pressure increases, electronic structure changes suppress superconductivity, with a shift in the VHS peak and a decrease in p-orbital contributions, leading to a Tc drop near zero at 400 GPa. These results suggest a potential phase transition above 400 GPa and offer insights for future high-pressure studies of arsenic. The electronic properties are calculated using density functional theory (DFT) implemented in the CASTEP code, employing the projector augmented-wave (PAW) method for the plane-wave expansion. The exchange-correlation interaction is described using the PBE functional within the generalized gradient approximation (GGA). Electron-phonon coupling (EPC) and superconducting properties are computed with the QUANTUM ESPRESSO code, utilizing the optimized norm-conserving Vanderbilt pseudopotential (ONCVPSP).

Predicting superconducting properties from first principles-especially in non-equilibrium conditions-is computationally intensive. Here, we propose a more efficient approach by using the electron localization function (ELF) as a proxy for estimating the superconducting critical temperature T C. Through first-principles calculations, we investigate how coupling conventional superconductors to an optical cavity-without external driving-modifies their phonon properties and electron-phonon interactions via vacuum fluctuations alone. We focus on three representative materials: lead (Pb), niobium (Nb), and magnesium diboride (MgB2). Our methodology combines Density Functional Theory (DFT), Density Functional Perturbation Theory (DFPT), Quantum Electrodynamical Density Functional Theory (QEDFT), and Wannier-based electron-phonon coupling to solve the Eliashberg equations for T C. For the materials studied here, our results indicate that the ELF captures some trends in the superconducting behavior under light-matter coupling, suggesting it may serve as a low-cost descriptor to guide the screening or design of superconductors in equilibrium and cavity-modified regimes.

Experimental results suggest a feasible strategy for tuning the superconducting properties of MgB2 through the incorporation of an electroluminescent inhomogeneous phase. By introducing GaP electroluminescent inhomogeneous phases into MgB2, the effects of emission intensity variation on the sample structure, superconducting transition temperature, electrical transport behavior, and magnetic properties were systematically investigated. The results show that, at a fixed GaP addition level, the superconducting transition temperature Tc increases steadily from 38.2 K to 39.6 K with increasing emission intensity of the inhomogeneous phase, corresponding to a maximum enhancement of approximately 1.4 K. Meanwhile, the zero-resistance temperature shifts upward synchronously, indicating that the entire superconducting transition region moves toward higher temperatures. Raman measurements show that the peak position and linewidth of the E2g phonon mode evolve systematically with emission intensity, while the electron-phonon coupling parameter λ exhibits a trend consistent with that of Tc. In addition, the nanoscale dispersed distribution of the GaP inhomogeneous phase, together with the interface/defect structures it introduces, appears to promote sample densification and enhance flux pinning, resulting in an increase in the critical current density Jc by approximately 69% at 20 K in self-field and an enhancement of the irreversibility field Hirr by about 31.5%. These results suggest that, beyond the effect of static inhomogeneous-phase incorporation, the luminescence-activated state under bias excitation is likely involved in modulating the superconducting response of MgB2. This work provides a new experimental perspective for synergistically regulating the properties of conventional superconductors through the combined effects of inhomogeneous phases and excited states.

In this study we revealed the effect of scandium doping on the electronic and superconducting properties of the MgB2 compound. Calculations demonstrate that Sc substitutes for Mg atoms, acting as an electron donor. Mg substitution diminishes the density of states in the σ-band and attenuates the electron-phonon coupling, thereby elucidating the reduction in critical temperature. Simultaneously, Sc-induced microstructural defects serve as effective pinning centers, thereby improving the critical current density. The established separation of electronic and microstructural effects allows for the targeted modification of MgB2 properties.

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