Interplay between Topological States and Rashba States as Manifested on Surface Steps at Room Temperature.

The unique spin texture of quantum states in topological materials underpins many proposed spintronic applications. However, realizations of such great potential are stymied by perturbations, such as temperature and local fields imposed by impurities and defects, that can render a promising quantum state uncontrollable. Here, we report room-temperature scanning tunneling microscopy/spectroscopy observation of interaction between Rashba states and topological surface states, which manifests local electronic structure along step edges controllable by the layer thickness of thin films. The first-principles theoretical calculation elucidates the robust Rashba states coexisting with topological surface states along the surface steps with characteristic spin textures in momentum space. Furthermore, the Rashba edge states can be switched off by reducing the thickness of a topological insulator Bi2Se3 to bolster their interaction with the hybridized topological surface states. The study unveils a manipulating mechanism of the spin textures at room temperature, reinforcing the necessity of thin film technology in controlling the quantum states.

Interfacially Enhanced Superconductivity in Fe(Te,Se)/Bi4Te3 Heterostructures.

Realizing topological superconductivity by integrating high-transition-temperature (TC) superconductors with topological insulators can open new paths for quantum computing applications. Here, a new approach is reported for increasing the superconducting transition temperature ( T C onset ) $( {T_{\mathrm{C}}^{{\mathrm{onset}}}} )$ by interfacing the unconventional superconductor Fe(Te,Se) with the topological insulator Bi-Te system in the low-Se doping regime, near where superconductivity vanishes in the bulk. The critical finding is that the T C onset $T_{\mathrm{C}}^{{\mathrm{onset}}}$ of Fe(Te,Se) increases from nominally non-superconducting to as high as 12.5 K when Bi2Te3 is replaced with the topological phase Bi4Te3. Interfacing Fe(Te,Se) with Bi4Te3 is also found to be critical for stabilizing superconductivity in monolayer films where T C onset $T_{\mathrm{C}}^{{\mathrm{onset}}}$ can be as high as 6 K. Measurements of the electronic and crystalline structure of the Bi4Te3 layer reveal that a large electron transfer, epitaxial strain, and novel chemical reduction processes are critical factors for the enhancement of superconductivity. This novel route for enhancing TC in an important epitaxial system provides new insight on the nature of interfacial superconductivity and a platform to identify and utilize new electronic phases.

Coherent light control of a metastable hidden state.

Metastable phases present a promising route to expand the functionality of complex materials. Of particular interest are light-induced metastable phases that are inaccessible under equilibrium conditions, as they often host new, emergent properties switchable on ultrafast timescales. However, the processes governing the trajectories to such hidden phases remain largely unexplored. Here, using time- and angle-resolved photoemission spectroscopy, we investigate the ultrafast dynamics of the formation of a hidden quantum state in the layered dichalcogenide 1T-TaS2 upon photoexcitation. Our results reveal the nonthermal character of the transition governed by a collective charge-density-wave excitation. Using a double-pulse excitation of the structural mode, we show vibrational coherent control of the phase-transition efficiency. Our demonstration of exceptional control, switching speed, and stability of the hidden state are key for device applications at the nexus of electronics and photonics.

Emergent Magnetism with Continuous Control in the Ultrahigh-Conductivity Layered Oxide PdCoO2.

The current challenge to realizing continuously tunable magnetism lies in our inability to systematically change properties, such as valence, spin, and orbital degrees of freedom, as well as crystallographic geometry. Here, we demonstrate that ferromagnetism can be externally turned on with the application of low-energy helium implantation and can be subsequently erased and returned to the pristine state via annealing. This high level of continuous control is made possible by targeting magnetic metastability in the ultrahigh-conductivity, nonmagnetic layered oxide PdCoO2 where local lattice distortions generated by helium implantation induce the emergence of a net moment on the surrounding transition metal octahedral sites. These highly localized moments communicate through the itinerant metal states, which trigger the onset of percolated long-range ferromagnetism. The ability to continuously tune competing interactions enables tailoring precise magnetic and magnetotransport responses in an ultrahigh-conductivity film and will be critical to applications across spintronics.

Monolayer Superconductivity and Tunable Topological Electronic Structure at the Fe(Te,Se)/Bi2 Te3 Interface.

The interface between 2D topological Dirac states and an s-wave superconductor is expected to support Majorana-bound states (MBS) that can be used for quantum computing applications. Realizing these novel states of matter and their applications requires control over superconductivity and spin-orbit coupling to achieve spin-momentum-locked topological interface states (TIS) which are simultaneously superconducting. While signatures of MBS have been observed in the magnetic vortex cores of bulk FeTe0.55 Se0.45 , inhomogeneity and disorder from doping make these signatures unclear and inconsistent between vortices. Here superconductivity is reported in monolayer (ML) FeTe1-y Sey (Fe(Te,Se)) grown on Bi2 Te3 by molecular beam epitaxy (MBE). Spin and angle-resolved photoemission spectroscopy (SARPES) directly resolve the interfacial spin and electronic structure of Fe(Te,Se)/Bi2 Te3 heterostructures. For y = 0.25, the Fe(Te,Se) electronic structure is found to overlap with the Bi2 Te3 TIS and the desired spin-momentum locking is not observed. In contrast, for y = 0.1, reduced inhomogeneity measured by scanning tunneling microscopy (STM) and a smaller Fe(Te,Se) Fermi surface with clear spin-momentum locking in the topological states are found. Hence, it is demonstrated that the Fe(Te,Se)/Bi2 Te3 system is a highly tunable platform for realizing MBS where reduced doping can improve characteristics important for Majorana interrogation and potential applications.

Safety assessment of Mpp75Aa1.1, a new ETX_MTX2 protein from Brevibacillus laterosporus that controls western corn rootworm.

The recently discovered insecticidal protein Mpp75Aa1.1 from Brevibacillus laterosporus is a member of the ETX_MTX family of beta-pore forming proteins (ß-PFPs) expressed in genetically modified (GM) maize to control western corn rootworm (WCR; Diabrotica virgifera virgifera LeConte). In this manuscript, bioinformatic analysis establishes that although Mpp75Aa1.1 shares varying degrees of similarity to members of the ETX_MTX2 protein family, it is unlikely to have any allergenic, toxic, or otherwise adverse biological effects. The safety of Mpp75Aa1.1 is further supported by a weight of evidence approach including evaluation of the history of safe use (HOSU) of ETX_MTX2 proteins and Breviballus laterosporus. Comparisons between purified Mpp75Aa1.1 protein and a poly-histidine-tagged (His-tagged) variant of the Mpp75Aa1.1 protein demonstrate that both forms of the protein are heat labile at temperatures at or above 55°C, degraded by gastrointestinal proteases within 0.5 min, and have no adverse effects in acute mouse oral toxicity studies at a dose level of 1920 or 2120 mg/kg body weight. These results support the use of His-tagged proteins as suitable surrogates for assessing the safety of their non-tagged parent proteins. Taken together, we report that Mpp75Aa1.1 is the first ETX-MTX2 insecticidal protein from B. laterosporus and displays a similar safety profile as typical Cry proteins from Bacillus thuringiensis.

Anomalously strong near-neighbor attraction in doped 1D cuprate chains.

In the cuprates, one-dimensional (1D) chain compounds provide a distinctive opportunity to understand the microscopic physics, owing to the availability of reliable theories. However, progress has been limited by the challenge of controllably doping these materials. We report the synthesis and spectroscopic analysis of the 1D cuprate Ba2-xSrxCuO3+δ over a wide range of hole doping. Our angle-resolved photoemission experiments reveal the doping evolution of the holon and spinon branches. We identify a prominent folding branch whose intensity fails to match predictions of the simple Hubbard model. An additional strong near-neighbor attraction, which may arise from coupling to phonons, quantitatively explains experiments for all accessible doping levels. Considering structural and quantum chemistry similarities among cuprates, this attraction may play a similarly important role in high-temperature cuprate superconductors.

Magic Doping and Robust Superconductivity in Monolayer FeSe on Titanates.

The enhanced superconductivity in monolayer FeSe on titanates opens a fascinating pathway toward the rational design of high-temperature superconductors. Utilizing the state-of-the-art oxide plus chalcogenide molecular beam epitaxy systems in situ connected to a synchrotron angle-resolved photoemission spectroscope, epitaxial LaTiO3 layers with varied atomic thicknesses are inserted between monolayer FeSe and SrTiO3, for systematic modulation of interfacial chemical potential. With the dramatic increase of electron accumulation at the LaTiO3/SrTiO3 surface, providing a substantial surge of work function mismatch across the FeSe/oxide interface, the charge transfer and the superconducting gap in the monolayer FeSe are found to remain markedly robust. This unexpected finding indicate the existence of an intrinsically anchored "magic" doping within the monolayer FeSe systems.

Dichotomy of the photo-induced 2-dimensional electron gas on SrTiO3 surface terminations.

Oxide materials are important candidates for the next generation of electronics due to a wide array of desired properties, which they can exhibit alone or when combined with other materials. While SrTiO3 (STO) is often considered a prototypical oxide, it, too, hosts a wide array of unusual properties, including a 2-dimensional electron gas (2DEG), which can form at the surface when exposed to ultraviolet (UV) light. Using layer-by-layer growth of high-quality STO films, we show that the 2DEG only forms with the SrO termination and not with the TiO2 termination, contrary to expectation. This dichotomy of the observed angle-resolved photoemission spectroscopy (ARPES) spectra is similarly seen in BaTiO3 (BTO), in which the 2DEG is only observed for BaO-terminated films. These results will allow for a deeper understanding and better control of the electronic structure of titanate films, substrates, and heterostructures.

Bacillus thuringiensis Cry1Da_7 and Cry1B.868 Protein Interactions with Novel Receptors Allow Control of Resistant Fall Armyworms, Spodoptera frugiperda (J.E. Smith).

Two new modified Bacillus thuringiensis (Bt) proteins, Cry1Da_7 and Cry1B.868, with activity against fall armyworms (FAW), Spodoptera frugiperda (J.E. Smith), were evaluated for their potential to bind new insect receptors compared to proteins currently deployed as plant-incorporated protectants (PIPs) in row crops. Results from resistant insect bioassays, disabled insecticidal protein (DIP) bioassays, and cell-based assays using insect cells expressing individual receptors demonstrate that receptor utilizations of the newly modified Cry1Da_7 and Cry1B.868 proteins are distinct from each other and from those of commercially available Bt proteins such as Cry1F, Cry1A.105, Cry2Ab, and Vip3A. Accordingly, these two proteins target different insect proteins in FAW midgut cells and when pyramided together should provide durability in the field against this economically important pest.IMPORTANCE There is increased concern with the development of resistance to insecticidal proteins currently expressed in crop plants, especially against high-resistance-risk pests such as fall armyworm (FAW), Spodoptera frugiperda, a maize pest that already has developed resistance to Bacillus thuringiensis (Bt) proteins such as Cry1F. Lepidopteran-specific proteins that bind new insect receptors will be critical in managing current Cry1F-resistant FAW and delaying future resistance development. Results from resistant insect assays, disabled insecticidal protein (DIP) bioassays, and cell-based assays using insect cells expressing individual receptors demonstrate that target receptors of the Cry1Da_7 and Cry1B.868 proteins are different from each other and from those of commercially available Bt proteins such as Cry1F, Cry1A.105, Cry2Ab, and Vip3A. Therefore, pyramiding these two new proteins in maize will provide durable control of this economically important pest in production agriculture.

HfSe2 and ZrSe2: Two-dimensional semiconductors with native high-κ oxides.

The success of silicon as a dominant semiconductor technology has been enabled by its moderate band gap (1.1 eV), permitting low-voltage operation at reduced leakage current, and the existence of SiO2 as a high-quality "native" insulator. In contrast, other mainstream semiconductors lack stable oxides and must rely on deposited insulators, presenting numerous compatibility challenges. We demonstrate that layered two-dimensional (2D) semiconductors HfSe2 and ZrSe2 have band gaps of 0.9 to 1.2 eV (bulk to monolayer) and technologically desirable "high-κ" native dielectrics HfO2 and ZrO2, respectively. We use spectroscopic and computational studies to elucidate their electronic band structure and then fabricate air-stable transistors down to three-layer thickness with careful processing and dielectric encapsulation. Electronic measurements reveal promising performance (on/off ratio > 106; on current, ~30 µA/µm), with native oxides reducing the effects of interfacial traps. These are the first 2D materials to demonstrate technologically relevant properties of silicon, in addition to unique compatibility with high-κ dielectrics, and scaling benefits from their atomically thin nature.

Ubiquitous strong electron-phonon coupling at the interface of FeSe/SrTiO3.

The observation of replica bands in single-unit-cell FeSe on SrTiO3 (STO)(001) by angle-resolved photoemission spectroscopy (ARPES) has led to the conjecture that the coupling between FeSe electrons and the STO phonons are responsible for the enhancement of Tc over other FeSe-based superconductors. However the recent observation of a similar superconducting gap in single-unit-cell FeSe/STO(110) raised the question of whether a similar mechanism applies. Here we report the ARPES study of the electronic structure of FeSe/STO(110). Similar to the results in FeSe/STO(001), clear replica bands are observed. We also present a comparative study of STO(001) and STO(110) bare surfaces, and observe similar replica bands separated by approximately the same energy, indicating this coupling is a generic feature of the STO surfaces and interfaces. Our findings suggest that the large superconducting gaps observed in FeSe films grown on different STO surface terminations are likely enhanced by a common mechanism.

Invited Article: High resolution angle resolved photoemission with tabletop 11 eV laser.

We developed a table-top vacuum ultraviolet (VUV) laser with 113.778 nm wavelength (10.897 eV) and demonstrated its viability as a photon source for high resolution angle-resolved photoemission spectroscopy (ARPES). This sub-nanosecond pulsed VUV laser operates at a repetition rate of 10 MHz, provides a flux of 2 × 10(12) photons/s, and enables photoemission with energy and momentum resolutions better than 2 meV and 0.012 Å(-1), respectively. Space-charge induced energy shifts and spectral broadenings can be reduced below 2 meV. The setup reaches electron momenta up to 1.2 Å(-1), granting full access to the first Brillouin zone of most materials. Control over the linear polarization, repetition rate, and photon flux of the VUV source facilitates ARPES investigations of a broad range of quantum materials, bridging the application gap between contemporary low energy laser-based ARPES and synchrotron-based ARPES. We describe the principles and operational characteristics of this source and showcase its performance for rare earth metal tritellurides, high temperature cuprate superconductors, and iron-based superconductors.

Direct spectroscopic evidence for phase competition between the pseudogap and superconductivity in Bi2Sr2CaCu2O(8+δ).

In the high-temperature (T(c)) cuprate superconductors, a growing body of evidence suggests that the pseudogap phase, existing below the pseudogap temperature T*, is characterized by some broken electronic symmetries distinct from those associated with superconductivity. In particular, recent scattering experiments have suggested that charge ordering competes with superconductivity. However, no direct link of an interplay between the two phases has been identified from the important low-energy excitations. Here, we report an antagonistic singularity at T(c) in the spectral weight of Bi2Sr2CaCu2O(8+δ) as compelling evidence for phase competition, which persists up to a high hole concentration p ~ 0.22. Comparison with theoretical calculations confirms that the singularity is a signature of competition between the order parameters for the pseudogap and superconductivity. The observation of the spectroscopic singularity at finite temperatures over a wide doping range provides new insights into the nature of the competitive interplay between the two orders and the complex phase diagram near the pseudogap critical point.

Laparoscopic extravesical reimplantation for postpubertal vesicoureteral reflux.

BACKGROUND AND PURPOSE: Postpubertal vesicoureteral reflux is a rare occurrence. In the adolescent group, its repair can be a challenging open procedure. We present our preliminary experience with laparoscopic extravesical ureteral reimplantation for postpubertal vesicoureteral reflux. PATIENTS AND METHODS: Six female patients with a mean age of 18.7 years presented with recurrent urinary tract infection secondary to vesicoureteral reflux. The indications for treatment were febrile urinary tract infection, recurrent pyelonephritis, renal scarring, and breakthrough urinary tract infection. The reflux was unilateral in all patients at the time of treatment, but one patient had previously experienced bilateral reflux and had persistent left-sided reflux following subureteral injection of Durasphere. This patient underwent bilateral laparoscopic extravesical ureteral reimplantation. RESULTS: The mean operative times for the unilateral and bilateral procedures were 1.75 hours and 3.75 hours, respectively. The average length of stay in the hospital was 36 hours; five patients went home in <24 hours. The mean time to resumption of full activity was 8 days. All six patients had resolution of vesicoureteral reflux, as shown by radiographic studies, with a mean follow-up of 11.4 months. CONCLUSION: Laparoscopic extravesical ureteral reimplantation for postpubertal vesicoureteral reflux has excellent outcomes with minimal postoperative morbidity. Long-term radiographic follow-up is needed.

Initial report of retroperitoneoscopic renal surgery in a patient with factor VIII deficiency (classic hemophilia).

Bleeding disorders are generally considered absolute contraindications to laparoscopic surgery. We believe laparoscopic/retroperitoneoscopic renal surgery is an optimal choice in patients with hemophilia, because it minimizes tissue trauma. We present a case of successful retroperitoneoscopic renal surgery in a patient with factor VIII deficiency with a perinephric abscess that failed less invasive treatments. A fully equipped coagulation laboratory, experienced hematologists, and an experienced laparoscopic surgeon play a large role in the outcome in patients with bleeding disorders undergoing minimally invasive procedures. We conclude that although uncorrected bleeding disorders are absolute contraindications for surgical procedures, those that are corrected and appropriately monitored are not.

Concomitant intraoperative renal artery embolization and resection of complex renal carcinoma.

BACKGROUND: Renal cell carcinoma, which has the propensity for rapid enlargement and local invasion, may present a surgical challenge, in part because of extensive vascularity. Conventional treatment typically involves staged preoperative renal artery embolization followed by nephrectomy after 1 or 2 days. We evaluated the clinical outcome of concomitant intraoperative embolization and nephrectomy. METHODS: Over 7 years, eight patients with renal cell carcinoma underwent combined intraoperative renal artery coil embolization and nephrectomy. A cohort of 14 patients who underwent staged renal embolization and nephrectomy during the same period served as the control group. Renal tumor embolization was achieved via percutaneous femoral artery approach, followed by coil placement in the distal portion of the main renal artery. Complete renal artery embolization was confirmed with intraoperative angiography. Nephrectomy was performed either concomitantly or after renal artery embolization, dependent on treatment group. Intraoperative data, clinical outcome, and hospital cost were compared between the two groups. RESULTS: Renal artery embolization and nephrectomy were successfully performed in all patients. There was no perioperative mortality. Mean hospital length of stay in the combined and staged treatment groups was 5.6 +/- 1.3 days and 10.2 +/- 3.2 days, respectively. Post-infarction syndrome developed in four patients (36%) in the staged group, compared with no patients in the combined treatment group. Decreased room cost and radiology cost was noted in the combined treatment group compared with the staged group. Mean total hospital cost was significantly less in patients who underwent the combined treatment compared with the staged treatment approach (mean difference, US dollars 9214; P =.02) During mean follow-up of 36 months, six patients (27%) died of unrelated causes. There was no evidence of tumor recurrence in surviving patients. DISCUSSION: In patients with renal cell carcinoma, combined renal embolization and nephrectomy minimizes patient discomfort and post-infarction syndrome associated with traditional staged treatment. Moreover, it is associated with reduced hospital costs, due in part to decreased hospital length of stay. Vascular surgeons with endovascular skills are well suited to perform intraoperative renal artery embolization. Use of adjunctive endovascular techniques to facilitate large open procedures is a growing role for the endovascular-competent vascular surgeon.

Incidence of postoperative adhesion formation after transperitoneal genitourinary laparoscopic surgery.

OBJECTIVES: To evaluate adhesion formation after urologic laparoscopy, a multi-institutional review was conducted among adult patients who underwent a second procedure after an initial transperitoneal laparoscopic procedure. Adhesion formation after abdominal surgery remains a major cause of postoperative morbidity. Peritoneal adhesions result in hospitalizations and interventions that result in healthcare costs of more than 1 billion dollars annually. The risk of adhesion formation from transperitoneal genitourinary laparoscopy in adults has not been previously studied. METHODS: Twenty-seven patients (mean age 45.5 years, range 24 to 71) were identified who underwent a second laparoscopic procedure after their initial urologic laparoscopic procedure was performed. The mean time between the procedures was 11.4 months (range 8 days to 38 months). At the time of the repeated laparoscopy or open surgery, the peritoneal cavity was examined and mapped for type (grade), extent (length), and location of any adhesions at the operative and trocar sites. The adhesions were graded as 0, no adhesions; 1, flimsy; 2, dense; and 3, cohesive. The extent was graded as 0, no adhesions; 1, less than 2 cm; 2, 2.1 to 10 cm; 3, greater than 10.1 cm. RESULTS: Overall, adhesions occurred in 6 (22.2%) of 27 patients. Operative site adhesions occurred in only 3 (8.2%) of 34 possible operative sites (gastric augmentation cystoplasty, renal cyst ablation, nephropexy). Trocar site adhesions occurred in 4 (3.5%) of 114 possible sites (two nephrectomies, one cyst decortication, and one orchiectomy). All adhesions were classified as grade 1 and extent 1, except for a single grade 2, extent 2 adhesion. In most patients, retroperitonealization occurred with minimal or no scarring noted. None of the patients developed symptoms as a result of the adhesion formation. CONCLUSIONS: Although intraperitoneal adhesions do occur with adult urologic laparoscopy, the incidence is low. Also, in the few patients who do form adhesions, they are flimsy and short. This evidence, when contrasted with the available data on adhesion formation after open surgery, suggests that transperitoneal laparoscopic approaches to genitourinary surgery may have advantages over traditional open transperitoneal approaches by lowering the incidence and severity of adhesion formation.