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1. Layer-Dependent Charge-State Lifetime of Single Se Vacancies in ${\mathrm{WSe}}_2$

   https://doi.org/10.1103/PhysRevLett.134.076201  

   Bobzien, Laric; Allerbeck, Jonas; Krane, Nils; Ortega-Guerrero, Andres; Wang, Zihao; Figueroa, Daniel_E Cintron; Dong, Chengye; Pignedoli, Carlo A; Robinson, Joshua A; Schuler, Bruno (February 2025, Physical Review Letters)

   Defect engineering in two-dimensional semiconductors has been exploited to tune the optoelectronic properties and introduce new quantum states in the band gap. Chalcogen vacancies in transition metal dichalcogenides in particular have been found to strongly impact charge carrier concentration and mobility in 2D transistors as well as feature subgap emission and single-photon response. In this Letter, we investigate the layer-dependent charge-state lifetime of Se vacancies in ${\mathrm{WSe}}_2$ . In one monolayer ${\mathrm{WSe}}_2$ , we observe ultrafast charge transfer from the lowest unoccupied orbital of the top Se vacancy to the graphene substrate within $(1\pm 0.2)\mathrm{ps}$ measured via the current saturation in scanning tunneling approach curves. For Se vacancies decoupled by transition metal dichalcogenide (TMD) multilayers, we find a subexponential increase of the charge lifetime from $(62\pm 14)\mathrm{ps}$ in bilayer to a few nanoseconds in four-layer ${\mathrm{WSe}}_2$ , alongside a reduction of the defect state binding energy. Additionally, we attribute the continuous suppression and energy shift of the $dI/dV$ in-gap defect state resonances at very close tip-sample distances to a current saturation effect. Our results provide a key measure of the layer-dependent charge transfer rate of chalcogen vacancies in TMDs. Published by the American Physical Society2025 

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2. Electronic Band Structure of a Superconducting Nickelate Probed by the Seebeck Coefficient in the Disordered Limit

   https://doi.org/10.1103/PhysRevX.14.041021  

   Grissonnanche, G; Pan, G A; LaBollita, H; Segedin, D Ferenc; Song, Q; Paik, H; Brooks, C M; Beauchesne-Blanchet, E; Santana_González, J L; Botana, A S; et al (October 2024, Physical Review X)

   Superconducting nickelates are a new family of strongly correlated electron materials with a phase diagram closely resembling that of superconducting cuprates. While analogy with the cuprates is natural, very little is known about the metallic state of the nickelates, making these comparisons difficult. We probe the electronic dispersion of thin-film superconducting five-layer ( $n=5$ ) and metallic three-layer ( $n=3$ ) nickelates by measuring the Seebeck coefficient $S$ . We find a temperature-independent and negative $S/T$ for both $n=5$ and $n=3$ nickelates. These results are in stark contrast to the strongly temperature-dependent $S/T$ measured at similar electron filling in the cuprate ${\mathrm{La}}_{1.36}{\mathrm{Nd}}_{0.4}{\mathrm{Sr}}_{0.24}{\mathrm{CuO}}_4$ . The electronic structure calculated from density-functional theory can reproduce the temperature dependence, sign, and amplitude of $S/T$ in the nickelates using Boltzmann transport theory. This demonstrates that the electronic structure obtained from first-principles calculations provides a reliable description of the fermiology of superconducting nickelates and suggests that, despite indications of strong electronic correlations, there are well-defined quasiparticles in the metallic state. Finally, we explain the differences in the Seebeck coefficient between nickelates and cuprates as originating in strong dissimilarities in impurity concentrations. Our study demonstrates that the high elastic scattering limit of the Seebeck coefficient reflects only the underlying band structure of a metal, analogous to the high magnetic field limit of the Hall coefficient. This opens a new avenue for Seebeck measurements to probe the electronic band structures of relatively disordered quantum materials. Published by the American Physical Society2024 

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3. Enhanced stability and bulk superconducting properties of Ag intercalated Bi _1.6 Pb _0.4 Sr ₂ Ca ₂ Cu ₃ O ${}_{10+\delta }$

   https://doi.org/10.1088/1361-6668/ae5690  

   Gonzalez_Arevalo, D; Do, Huu T; Mark, Alexander C; Rodriguez, David; Zangeneh, Danial; Klie, Robert F; Hemley, Russell J; Man, N K (April 2026, Superconductor Science and Technology)

   Abstract Cuprate high-temperature superconductors (HTSCs) have long stood a promising candidates for various applications due to their high critical temperature ( $T_{\mathrm{c}}$ ) at ambient pressure. Practical limitations such as low bulk critical current densities ( $J_{\mathrm{c}}^{\mathrm{B}}$ ), sample inhomogeneities and chemical instability, however, have hindered their applicability. Increasing ${\mathit{T}}_{\mathrm{c}}$ , $J_{\mathrm{c}}^{\mathrm{B}}$ and the upper critical fields as well as maintaining the chemical stability in cuprates are therefore major goals for these materials science. Here, we characterize the electronic and structural properties of an Ag intercalated ${\mathrm{Bi}}_{1.6}{\mathrm{Pb}}_{0.4}{\mathrm{Sr}}_2{\mathrm{Ca}}_2{\mathrm{Cu}}_3{\mathrm{O}}_{10+\delta }$ sample prepared using a novel growth technique. The sample demonstrates enhanced electrical properties that have remained nearly constant over 8 years, while the non-silver Bi-2223 exhibits much degradation in both high- $T_{\mathrm{c}}$ fractional phase and superconducting properties. We correlate these bulk electronic properties with structural probes to determine the critical role of Ag in these samples. The enhanced properties of these Ag intercalated cuprates suggest novel synthesis pathways will be key in developing more practical superconductors for applications. 

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4. Dirac Fermion Cloning, Moiré Flat Bands and Magic Lattice Constants in Epitaxial Monolayer Graphene

   https://doi.org/10.1002/adma.202200625  

   Lu, Qiangsheng; Le, Congcong; Zhang, Xiaoqian; Cook, Jacob; He, Xiaoqing; Zarenia, Mohammad; Vaninger, Mitchel; Miceli, Paul F.; Singh, David J.; Liu, Chang; et al (April 2022, Advanced Materials)

   Tuning interactions between Dirac states in graphene has attracted enormous interest because it can modify the electronic spectrum of the two-dimensional material, enhance electron correlations, and give rise to novel condensed-matter phases such as superconductors, Mott insulators, Wigner crystals and quantum anomalous Hall insulators. Previous works predominantly focus on the flat band dispersion of coupled Dirac states from different twisted graphene layers. In this work, we propose a new route to realizing flat band physics in monolayer graphene under a periodic modulation from substrates. We take graphene/SiC heterostructure as a prototypical example and demonstrate experimentally that the substrate modulation leads to Dirac fermion cloning and consequently, the proximity of the two Dirac cones of monolayer graphene in momentum space. Our theoretical modeling captures the cloning mechanism of Dirac states and indicates that Moiré flat bands can emerge at certain magic lattice constants of the substrate, specifically when the period of modulation becomes nearly commensurate with the (√3×√3)𝑅30∘ supercell of graphene. The results show that epitaxial single monolayer graphene on suitable substrates is a promising platform for exploring exotic many-body quantum phases arising from interactions between Dirac electrons. 

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5. An efficient quantum algorithm for ab initio approximations of non-linear response functions

   https://doi.org/10.1038/s41534-025-01026-9  

   Kharazi, Tyler; Stetina, Torin F; Ko, Liwen; Low, Guang Hao; Whaley, K Birgitta (December 2025, npj Quantum Information)

   Abstract We develop and analyze a fault-tolerant quantum algorithm for non-linear response properties of molecular and condensed phase systems. We consider a semi-classical description in which the electronic degrees of freedom are treated quantum mechanically and the light is treated as a classical field interacting via the electric dipole approximation. We use the technique of eigenstate filtering, to efficiently resolve excitation energies for dominant dipole transitions. When applied to the electronic structure Hamiltonian with double factorized representation, each significant spectral line can be approximated to a width of ±γ, and to a height of ±ϵwith$$O\left({N}^{6}{\eta }^{2}{\gamma }^{-1}{\epsilon }^{-1}\log (1/\epsilon )\right)$$ $O\left(N^6{\eta }^2{\gamma }^{-1}{ϵ}^{-1}\log \left(1/ϵ\right)\right)$ queries to the block encoding of the unperturbed electronic structure Hamiltonian forηelectrons overNbasis functions. These quantities can be used to compute thenth order response functions for non-linear spectroscopies under limited assumptions using$$\widetilde{O}\left({N}^{5n+1}{\eta }^{n+1}/{\gamma }^{n}\epsilon \right)$$ $\tilde{O}\left(N^{5n+1}{\eta }^{n+1}/{\gamma }^nϵ\right)$ queries to the block encoding of the Hamiltonian. 

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