We investigate the influence of Co intercalation and altermagnetic order on the lattice dynamics of the layered compound Co_1/4NbSe_2. Polarization-resolved Raman spectroscopy, supported by density-functional theory, enables identification of six Raman-active phonons. Co intercalation drives a substantial reconstruction of the vibrational spectrum through zone folding of NbSe_2 phonons, producing hybridized modes with mixed zone-center and zone-boundary character. Despite this, Co atoms do not participate in any Raman-active modes by symmetry, which is in marked contrast to related 1/3 compounds where intercalant modes do contribute to the Raman spectrum. Temperature-dependent Raman measurements across the altermagnetic transition show no discontinuities, which is consistent with short-range spin correlations in the quasi-one-dimensional Co chains. However, we find evidence for spin-phonon coupling in A_1g symmetry modes owing to their out-of-plane Se displacements. Our work demonstrates the substantial impact of intercalation on the vibrational properties of transition metal dichalcogenides and the presence of spin-phonon interactions in a newly discovered altermagnetic material.

Introduction The atomristor is an emerging device concept where an atomically thin 2D material serves as a resistive switching layer [1-2]. This offers a promising non-volatile memory technology for next-generation computing. Most previous works on transition metal dichalcogenide (TMD)-based atomristors used MoS 2 in a vertical (crossbar) device geometry [2]. Platinum diselenide (PtSe 2 ) is a rapidly emerging TMD family, offering a rare combination of high-mobility, air-stability, and CMOS-compatibility [3-5]. In this work, we turned PtSe 2 into an atomristor and thoroughly tested its switching behavior and mechanism in the lateral structure. This study helps to simplify device design and manufacturing while potentially facilitating a scaling study for PtSe 2 atomristors. Key Results Fig. 1 shows both the schematic diagram (1a) and the micrograph image (1b) of the lateral PtSe 2 atomristor device fabricated. The gold (Au) electrodes were lithographically patterned and deposited by physical vapor deposition (PVD) on a SiO 2 /Si wafer, and a separately prepared PtSe 2 film [5] was integrated on top using the DI water-assisted transfer technique. The choice of Au (a noble metal) as the electrodes was made to rule out any interfacial effects in the switching process. As seen in Fig. 2a, our device exhibited both SET (from high-resistance state to low-resistance state) and RESET (from low-resistance state to high-resistance state) transitions at a reasonable range of switching voltages (2-3 V). This is important because previously, it was predicted in the literature that an atomristor’s switching voltage would be too large in a lateral geometry [1]. Despite some high device-to-device variability observed (Fig. 2b), our results clearly suggest that a lateral atomristor device is feasible and may be governed by a different switching mechanism from a vertical atomristor, where the non-volatile, reversible switching has been understood in the framework of a dissociation-diffusion-adsorption model. To further study the switching mechanism of our lateral PtSe 2 atomristor, we performed both AFM (atomic force microscope, Figs. 3-4) and Raman spectroscopic characterizations (Fig. 5). The thickness of PtSe 2 is confirmed to be around 6-7 nm, implying that the resistive-switching does not require TMDs to be single or fewer layered in a lateral atomristor device geometry. The average roughness of the PtSe 2 surface is measured to be about 0.53 nm and 0.37 nm for the regions where PtSe 2 sits on top of the electrode (Au) and the substrate (SiO 2 ), respectively. This difference is attributed to the fact that Au electrodes were post-deposited in a device fabrication process using a PVD technique (thermal evaporation) while the industrial-grade, flat and smooth, SiO 2 -coated Si wafer was used as the substrate. Fig. 5 exhibits the Raman spectroscopy characteristic peaks of E g at ~ 179 cm -1 and A 1g at ~ 207 cm -1 , corresponding to the in-plane and out-of-plane vibration modes of 2D PtSe 2 layers. Because our Raman data shows a negligible difference between two regions (PtSe 2 on Au vs. SiO 2 ) in terms of peak positions and FWHM (full-width at half maximum) (6.2 to 6.5 cm -1 for E g and 7.6 to 7.9 cm -1 for A 1g ), the substrate effect along the transport pathway could be minimal. It is speculated that in a lateral PtSe 2 atomristor, the switching is primarily governed by the dissociation-adsorption of electrode atoms at the PtSe 2 /electrode interface. Significance Previously, various TMD materials have been explored for hysteretic resistive-switching behaviors [1]. However, a specific group of TMDs (mostly MoS 2 ) has been studied in-depth for atomristor applications (including cycling endurance and retention characteristics [2]) in a specific device geometry. This work will contribute to the field and lead researchers to re-think about the potential of Pt-based TMDs to become a useful material platform for non-volatile memory by fabricating and characterizing the PtSe 2 atomristor in a lateral structure. References [1] R. Ge et al., “A Library of Atomically Thin 2D Materials Featuring the Conductive-Point Resistive Switching Phenomenon,” Advanced Materials 33, 2007792 (2021). [2] R. Ge et al., “Atomristor: Nonvolatile Resistance Switching in Atomic Sheets of Transition Metal Dichalcogenides,” Nano Letters 18, 434 (2018). [3] S. S. Han et al., “High Mobility Transistors and Flexible Optical Synapses Enabled by Wafer-Scale Chemical Transformation of Pt-Based 2D Layers,” ACS Applied Materials & Interfaces 16, 36599 (2024). [4] S. S. Han et al., “Wafer-scale flexible 2D PtSe 2 layers with bi-directional wavelength tunability for fully optical synaptic operations,” 139, 110943 (2025). [5] S. S. Han et al., “Horizontal-to-Vertical Transition of 2D Layer Orientation in Low-Temperature Chemical Vapor Deposition-Grown PtSe 2 and Its Influences on Electrical Properties and Device Applications,” ACS Applied Materials & Interfaces 11, 13598 (2019). Figure 1

Abstract The assembly of molecular photonic wires (MPWs) on DNA scaffolds offers a powerful platform for controlling nanoscale energy transfer. This work demonstrates how the geometric configuration of an excitonic relay, composed of a cyanine (Cy5) dye dimer, regulates energy flow within an MPW. Exploiting linker chemistry, either H-type or J-type aggregates are selectively formed at room temperature. H-type dimers act as energy transfer inhibitors, while J-type dimers function as effective energy relays. In an optimized architecture, J-dimer MPWs outperform equivalent systems using monomeric relays. This performance is significantly amplified upon transitioning the system from solution to solid-state films, where the energy transfer efficiency of J-dimer wires is enhanced by up to 300% relative to monomeric versions. Experimental results also support approximating the dimers as single-point dipoles for Förster resonance energy transfer considerations. These results establish a robust strategy for engineering the optical properties of molecular materials, where nanoscale energy transport is precisely directed by controlling the geometry of excitonic aggregates.

Light polarization offers a powerful yet underexplored handle to control photoelectrochemical processes in two-dimensional (2D) semiconductors. Here, we demonstrate polarization-tunable photoelectrochemistry at anisotropic 2D ReS2 interfaces, providing a new strategy to manipulate light-driven charge dynamics. Using scanning electrochemical cell microscopy (SECCM) under controlled photoexcitation, we systematically probe how incident wavelength, layer thickness, and van der Waals stacking govern polarization sensitivity at the nanoscale. The dichroic ratio increases by ∼50% as the excitation wavelength approaches the band edge and decreases systematically with thickness, while the polarization phase shift grows with both wavelength and layer number due to ReS2 birefringence. By stacking ReS2 layers with controlled twist angles and thickness contrasts, we achieve programmable junction behavior ranging from nearly isotropic responses in 90°-twisted bilayers to layer-dominant anisotropy dictated by photogeneration balance. For arbitrary twist angles, the phase shifts of the individual layers add coherently, enabling predictive control of the angular response. This work establishes light polarization as a precise and versatile control knob for nanoscale photoelectrochemistry, offering a new paradigm for designing optoelectronic and photocatalytic devices with intrinsic polarization selectivity.

Ultrafast light-matter interaction has emerged as a mechanism to control the macroscopic properties of quantum materials. However, technological applications of photoinduced phases are limited by their ultrashort lifetimes and the low temperatures required for their stabilization. One such phase is the hidden metallic charge density wave state in 1T-TaS2, whose origin and stability above cryogenic temperatures remain the subject of debate. Here, we demonstrate that this phase can be stabilized at thermal equilibrium by accessing a mixed charge density wave order regime through thermal quenching. Using X-ray high-dynamic-range reciprocal space mapping and scanning tunnelling spectroscopy, we reveal the coexistence of commensurate charge density wave and hidden metallic charge density wave domains up to 210 K. Our findings show that each order parameter breaks basal plane mirror symmetry with different chiral orientations and induces out-of-plane unit cell tripling in the hidden phase. Despite metallic domain walls and a finite density of states, the bulk resistance remains insulating due to charge density wave stacking disorder. Our results establish the hidden state as a thermally stable phase and introduce an alternative mechanism for switchable metallic behaviour in thin flakes of 1T-TaS2 and similar materials with competing phases.

Phase-change memory (PCM) is a promising candidate for neuro-inspired, data-intensive artificial intelligence applications, which relies on the physical attributes of PCM materials including gradual change of resistance states and multilevel operation with low resistance drift. However, achieving these attributes simultaneously remains a fundamental challenge for PCM materials such as Ge2 Sb2 Te5 , the most commonly used material. Here bi-directional gradual resistance changes with ≈10× resistance window using low energy pulses are demonstrated in nanoscale PCM devices based on Ge4 Sb6 Te7 , a new phase-change nanocomposite material . These devices show 13 resistance levels with low resistance drift for the first 8 levels, a resistance on/off ratio of ≈1000, and low variability. These attributes are enabled by the unique microstructural and electro-thermal properties of Ge4 Sb6 Te7 , a nanocomposite consisting of epitaxial SbTe nanoclusters within the Ge-Sb-Te matrix, and a higher crystallization but lower melting temperature than Ge2 Sb2 Te5 . These results advance the pathway toward energy-efficient analog computing using PCM.

Quantum critical points separating weak ferromagnetic and paramagnetic phases trigger many novel phenomena. Dynamical spin fluctuations not only suppress the long-range order, but can also lead to unusual transport and even superconductivity. Combining quantum criticality with topological electronic properties presents a rare and unique opportunity. Here, by means of ab initio calculations and magnetic, thermal, and transport measurements, it is shown that the orthorhombic CoTe2 is close to ferromagnetism, which appears suppressed by spin fluctuations. Calculations and transport measurements reveal nodal Dirac lines, making it a rare combination of proximity to quantum criticality and Dirac topology.

Charge transfer (CT) cocrystals, molecular crystals composed of electron donating and accepting species, are being developed for applications in optoelectronics. Here we present optical and electronic characterization of the CT cocrystal phenothiazine-tetracyanoquinodimethane (PTZ-TCNQ). This material has a broad NIR absorption peak with an optical band edge less than 0.6 eV. We used density functional theory calculations to identify the origin of the low energy CT states and changes in the Raman spectra. We also demonstrate the fabrication of long, ribbon-like oriented cocrystals using an evaporative alignment method. Cocrystals grown on Si substrates were fabricated into organic field effect transistors. Despite theoretical predictions of ambipolarity, only electron conduction was observed, with mobilities on the order of 10-4 cm2 V-1 s-1. Measurements of the temperature dependence of the mobility indicated a superexchange mediated hopping mechanism for charge transport, with a characteristic scale of 0.19 eV.

Chalcogenides in perovskite and the related layered Ruddlesden-Popper crystal structures (chalcogenide perovskites for brevity) are an exciting family of semiconductors but remain experimentally little studied. Chalcogenide perovskites share crystal structures and some physical properties with ionic compounds such as oxide and halide perovskites, but the metal-chalcogen bonds responsible for semiconducting behavior are substantially more covalent than in these more-studied perovskites. Here, we use complementary experimental and theoretical methods to study how the mixed ionic-covalent Zr-S bonds support the electronic structure and physical properties of perovskite BaZrS3 and Ruddlesden-Popper Ba3Zr2S7. We apply theoretical methods to assign features of experimentally measured x-ray absorption spectroscopy (XAS) to particular orbital transitions, enabling a clear physical interpretation of angle-dependent, polarized XAS data measured on single-crystal samples, and an atomistic view of the covalent bonding network that facilitates charge transport. Polarized Raman measurements identify signatures of crystalline anisotropy in Ba3Zr2S7 and enable the first assignments of mode symmetry in this material. Infrared reflectivity reveals electronic transport properties that augur well for the use of chalcogenide perovskites in optoelectronic and energy-conversion technologies.

Cubic boron nitride (cBN) is a relatively less studied wide bandgap semiconductor despite its many promising mechanical, thermal, and electronic properties. We report on the electronic, structural, and optical characterization of commercial cBN crystal platelets. Temperature dependent transport measurements revealed the charge limited diode behavior of the cBN crystals. The equilibrium Fermi level was determined to be 0.47 eV below the conduction band, and the electron conduction was identified as n-type. Unirradiated dark and amber colored cBN crystals displayed broad photoluminescence emission peaks centered around different wavelengths. RC series zero phonon line defect emission peaks were observed at room temperature from the electron beam irradiated and oxygen ion implanted cBN crystals, making this material a promising candidate for high power microwave devices, next generation power electronics, and future quantum sensing applications.

Background: Quantum information science and technology (QIST) has progressed significantly in the last decade, such that it is no longer solely in the domain of research labs, but is now beginning to be developed for, and applied in, industrial applications and products. With the emergence of this new quantum industry, a new workforce trained in QIST skills and knowledge is needed. Research Questions: To help support the education and training of this workforce, universities and colleges require knowledge of the type of jobs available for their students and what skills and degrees are most relevant for those new jobs. What are these jobs, skills, and degrees? Methodology: We report on the results from a survey of 57 companies in the quantum industry, with the goal of elucidating the jobs, skills, and degrees that are relevant for this new workforce. Findings: We find a range of job opportunities from highly specific jobs, such as quantum algorithm developer and error correction scientist, to broader jobs categories within the business, software, and hardware sectors. These broader jobs require a range of skills, most of which are not quantum related. Furthermore, except for the highly specific jobs, companies that responded to the survey are looking for a range of degree levels to fill these new positions, from bachelors to masters to Ph.D.s. Contribution: With this knowledge, students, instructors, and university administrators can make informed decisions about how to address the challenge of increasing the future quantum workforce.

Two-dimensional (2D) materials that exhibit charge density waves (CDWs) have generated many research endeavors in the hopes of employing their exotic properties for various quantum-based technologies. Early investigations surrounding CDWs were mostly focused on bulk materials. However, applications for quantum devices have since required devices to be constructed from few-layer material to fully utilize the material's properties. This field has greatly expanded over the decades, warranting a focus on the computational efforts surrounding CDWs in 2D materials. In this review, we will cover ground in the following relevant, theory-driven subtopics for TaS2 and TaSe2: summary of general computational techniques and methods, atomic structures, Raman modes, and effects of confinement and dimensionality. Through understanding how the computational methods have enabled incredible advancements in quantum materials, one may anticipate the ever-expanding directions available for continued pursuit as the field brings us through the 21st century.

Two-dimensional (2D) materials that exhibit charge density waves (CDWs)—spontaneous reorganization of their electrons into a periodic modulation—have generated many research endeavors in the hopes of employing their exotic properties for various quantum-based technologies. Early investigations surrounding CDWs were mostly focused on bulk materials. However, applications for quantum devices require few-layer materials to fully utilize the emergent phenomena. The CDW field has greatly expanded over the decades, warranting a focus on the computational efforts surrounding them specifically in 2D materials. In this review, we cover ground in the following relevant theory-driven subtopics for TaS2 and TaSe2: summary of general computational techniques and methods, resulting atomic structures, the effect of electron–phonon interaction of the Raman scattering modes, the effects of confinement and dimensionality on the CDW, and we end with a future outlook. Through understanding how the computational methods have enabled incredible advancements in quantum materials, one may anticipate the ever-expanding directions available for continued pursuit as the field brings us through the 21st century.

Layered materials enable the assembly of a new class of heterostructures where lattice-matching is no longer a requirement. Interfaces in these heterostructures therefore become a fertile ground for unexplored physics as dissimilar phenomena can be coupled via proximity effects. In this article, we identify an unexpected photoluminescence (PL) peak when MoSe2 interacts with TiSe2. A series of temperature-dependent and spatially resolved PL measurements reveal that this peak is unique to the TiSe2–MoSe2 interface, is higher in energy compared to the neutral exciton, and exhibits exciton-like characteristics. The feature disappears at the TiSe2 charge density wave transition, suggesting that the density wave plays an important role in the formation of this new exciton. We present several plausible scenarios regarding the origin of this peak that individually capture some aspects of our observations but cannot fully explain this feature. These results therefore represent a fresh challenge for the theoretical community and provide a fascinating way to engineer excitons through interactions with charge density waves.

Alloyed transition metal dichalcogenides provide an opportunity for coupling band engineering with valleytronic phenomena in an atomically-thin platform. However, valley properties in alloys remain largely unexplored. We investigate the valley degree of freedom in monolayer alloys of the phase change candidate material WSe2(1-x)Te2x. Low temperature Raman measurements track the alloy-induced transition from the semiconducting 1H phase of WSe2 to the semimetallic 1Td phase of WTe2. We correlate these observations with density functional theory calculations and identify new Raman modes from W-Te vibrations in the 1H-phase alloy. Photoluminescence measurements show ultra-low energy emission features that highlight alloy disorder arising from the large W-Te bond lengths. Interestingly, valley polarization and coherence in alloys survive at high Te compositions and are more robust against temperature than in WSe2. These findings illustrate the persistence of valley properties in alloys with highly dissimilar parent compounds and suggest band engineering can be utilized for valleytronic devices.

A thorough understanding of native oxides is essential for designing semiconductor devices. Here, we report a study of the rate and mechanisms of spontaneous oxidation of bulk single crystals of ZrSxSe2-x alloys and MoS2. ZrSxSe2-x alloys oxidize rapidly, and the oxidation rate increases with Se content. Oxidation of basal surfaces is initiated by favorable O2 adsorption and proceeds by a mechanism of Zr-O bond switching, that collapses the van der Waals gaps, and is facilitated by progressive redox transitions of the chalcogen. The rate-limiting process is the formation and out-diffusion of SO2. In contrast, MoS2 basal surfaces are stable due to unfavorable oxygen adsorption. Our results provide insight and quantitative guidance for designing and processing semiconductor devices based on ZrSxSe2-x and MoS2 and identify the atomistic-scale mechanisms of bonding and phase transformations in layered materials with competing anions.

Efficient doping of 2D materials, including carrier type, concentration and mobility, is challenging but essential for enabling their future electronic and photonic applications. We are developing substitutional n- and p- doping of InSe semiconductor by introducing Sn and Zn, respectively, in the Bridgman bulk crystal growth. Electrical transport properties of undoped vs. n- and p- doped InSe crystals are compared by conducting Hall measurements on bulk crystals and FET transport measurements on exfoliated thin layers. Undoped InSe is intrinsically n-type in both bulk and thin-film forms, with [n]~3.5E14 cm-3 and mu values of up to 1,400 cm2 V-1 s-1 for thick layers at 300K. Carrier concentration in Sn-doped thick layers increases approximately two-fold, while the corresponding mobility reduces ~2 times at 300 K. Zn-doped InSe shows p- behavior for bulk InSe with [p]~7.9E13 cm-3 and mu~43 cm2 V-1 s-1 at 300 K, which reverts to ambipolar/n- type behavior for thin layers in FET devices.

An amendment to this paper has been published and can be accessed via a link at the top of the paper.

ZrS2, ZrSe2 and mixed alloy ZrSxSe2-x materials were achieved through chemical vapor transport. The incongruent melting system of Zr-S-Se formed crystalline layered flakes as a transport product that grew up to 2 cm in lateral size with cm-scale flakes consistently obtained for the entire compositional range exhibiting visible hexagonal features. Bulk flakes of the series ZrSxSe2-x (x = 0, 0.15, 0.3, 0.6, 1.05, 1.14, 1.51, 1.8 and 2) were analyzed through Raman spectroscopy revealing significant convolution of primary bonding modes and shifting of Raman features as a function of increasing sulfur composition. Additionally, activation of new modes not present in the pure compounds are observed as effects which result from disorder introduced into the crystal due to the random mixing of S-Se in the alloying process. Further structural characterization was performed via x-ray diffraction (XRD) on the layered flakes to evaluate the progression of layer spacing function of alloy composition which was found to range between 6.24 angstrom for ZrSe2 and 5.85 angstrom for ZrS2. Estimation of the compositional ratios of the alloy flakes through energy dispersive spectroscopy (EDS) large-area mapping verified the relation of the targeted source stoichiometry represented in the layered flakes. Atomic-resolution high angle annular dark field (HAADF)-scanning transmission electron microscopy (STEM) imaging was performed on the representative Zr (S0.5Se0.5)(2) alloy to validate the 1T atomic structure and observe the arrangement of the chalcogenide columns stacks. Additionally, selected area diffraction pattern generated from the [0 0 0 1] zone axis revealed the in-plane lattice parameter to be approximately 3.715 angstrom.

Alloyed transition metal dichalcogenides provide an opportunity for coupling band engineering with valleytronic phenomena in an atomically-thin platform. However, valley properties in alloys remain largely unexplored. We investigate the valley degree of freedom in monolayer alloys of the phase change candidate material WSe 2(1-x) Te 2x . Low temperature Raman measurements track the alloy-induced transition from the semiconducting 1H phase of WSe 2 to the semimetallic 1T d phase of WTe 2 . We correlate these observations with density functional theory calculations and identify new Raman modes from W-Te vibrations in the 1H-phase alloy. Photoluminescence measurements show ultra-low energy emission features that highlight alloy disorder arising from the large W-Te bond lengths. Interestingly, valley polarization and coherence in alloys survive at high Te compositions and are more robust against temperature than in WSe 2 . These findings illustrate the persistence of valley properties in alloys with highly dissimilar parent compounds and suggest band engineering can be utilized for valleytronic devices.