Resonance from antiferromagnetic spin fluctuations for superconductivity in UTe2.

Superconductivity originates from the formation of bound (Cooper) pairs of electrons that can move through the lattice without resistance below the superconducting transition temperature Tc (ref. 1). Electron Cooper pairs in most superconductors form anti-parallel spin singlets with total spin S = 0 (ref. 2), although they can also form parallel spin-triplet Cooper pairs with S = 1 and an odd parity wavefunction3. Spin-triplet pairing is important because it can host topological states and Majorana fermions relevant for quantum computation4,5. Because spin-triplet pairing is usually mediated by ferromagnetic (FM) spin fluctuations3, uranium-based materials near an FM instability are considered to be ideal candidates for realizing spin-triplet superconductivity6. Indeed, UTe2, which has a Tc ≈ 1.6 K (refs. 7,8), has been identified as a candidate for a chiral spin-triplet topological superconductor near an FM instability7-14, although it also has antiferromagnetic (AF) spin fluctuations15,16. Here we use inelastic neutron scattering (INS) to show that superconductivity in UTe2 is coupled to a sharp magnetic excitation, termed resonance17-23, at the Brillouin zone boundary near AF order. Because the resonance has only been found in spin-singlet unconventional superconductors near an AF instability17-23, its observation in UTe2 suggests that AF spin fluctuations may also induce spin-triplet pairing24 or that electron pairing in UTe2 has a spin-singlet component.

Experimental Observation and Spin Texture of Dirac Node Arcs in Tetradymite Topological Metals.

We report the observation of a nontrivial spin texture in Dirac node arcs, i.e., novel topological objects formed when Dirac cones of massless particles extend along an open one-dimensional line in momentum space. We find that such states are present in all the compounds of the tetradymite M_{2}Te_{2}X family (M=Ti, Zr, or Hf and X=P or As) regardless of the weak or strong character of the topological invariant. The Dirac node arcs in tetradymites are thus the simplest possible textbook example of a type-I Dirac system with a single spin-polarized node arc.

Rectal perforation after aquablation of the prostate: lessons learned the hard way.

INTRODUCTION: Transurethral resection of the prostate and open prostatectomy have been the standard of care for the surgical treatment of benign prostatic obstruction (BPO) over decades. New emerging techniques for the surgical management of BPO have been currently introduced, but might be associated with new, unusual complications. METHODS: We herewith report on two patients with a rectal perforation after aquablation treatment of BPO. RESULTS: In the first case, the diagnosis was made 2 days after the aquablation procedure due to unspecific postoperative symptoms. A complex combined open/endoscopic repair of the defect was carried out thereafter. As a consequence, a rectoscopy was routinely performed since then following each aquablation procedure. In the second case, intraoperative rectoscopy after uneventful aquablation revealed the rectal perforation. The perforation was clipped immediately with an over the scope-clip by colonoscopy. CONCLUSIONS: These two cases of a rectal perforation after aquablation of the prostate demonstrate an unusual complication and its complex management. Diagnostic delay complicates its treatment. Therefore, immediate rectoscopy should be performed routinely after the aquablation procedure.

Bulk Fermi Surfaces of the Dirac Type-II Semimetallic Candidates MAl_{3} (Where M=V, Nb, and Ta).

We report a de Haas-van Alphen (dHvA) effect study on the Dirac type-II semimetallic candidates MAl_{3} (where, M=V, Nb and Ta). The angular dependence of their Fermi surface (FS) cross-sectional areas reveals a remarkably good agreement with our first-principles calculations. Therefore, dHvA supports the existence of tilted Dirac cones with Dirac type-II nodes located at 100, 230 and 250 meV above the Fermi level ϵ_{F} for VAl_{3}, NbAl_{3} and TaAl_{3} respectively, in agreement with the prediction of broken Lorentz invariance in these compounds. However, for all three compounds we find that the cyclotron orbits on their FSs, including an orbit nearly enclosing the Dirac type-II node, yield trivial Berry phases. We explain this via an analysis of the Berry phase where the position of this orbit, relative to the Dirac node, is adjusted within the error implied by the small disagreement between our calculations and the experiments. We suggest that a very small amount of doping could displace ϵ_{F} to produce topologically nontrivial orbits encircling their Dirac node(s).

Quantum Critical Scaling in the Disordered Itinerant Ferromagnet UCo_{1-x}Fe_{x}Ge.

The Belitz-Kirkpatrick-Vojta (BKV) theory shows in excellent agreement with experiment that ferromagnetic quantum phase transitions (QPTs) in clean metals are generally first order due to the coupling of the magnetization to electronic soft modes, in contrast to the classical analogue that is an archetypical second-order phase transition. For disordered metals the BKV theory predicts that the second-order nature of the QPT is restored because the electronic soft modes change their nature from ballistic to diffusive. Our low-temperature magnetization study identifies the ferromagnetic QPT in the disordered metal UCo_{1-x}Fe_{x}Ge as the first clear example that exhibits the associated critical exponents predicted by the BKV theory.

Candidate Elastic Quantum Critical Point in LaCu_{6-x}Au_{x}.

The structural properties of LaCu_{6-x}Au_{x} are studied using neutron diffraction, x-ray diffraction, and heat capacity measurements. The continuous orthorhombic-monoclinic structural phase transition in LaCu_{6} is suppressed linearly with Au substitution until a complete suppression of the structural phase transition occurs at the critical composition x_{c}=0.3. Heat capacity measurements at low temperatures indicate residual structural instability at x_{c}. The instability is ferroelastic in nature, with density functional theory calculations showing negligible coupling to electronic states near the Fermi level. The data and calculations presented here are consistent with the zero temperature termination of a continuous structural phase transition suggesting that the LaCu_{6-x}Au_{x} series hosts an elastic quantum critical point.

Magnetic Ground States of the Rare-Earth Tripod Kagome Lattice Mg_{2}RE_{3}Sb_{3}O_{14} (RE=Gd,Dy,Er).

We present the structural and magnetic properties of a new compound family, Mg_{2}RE_{3}Sb_{3}O_{14} (RE=Gd,Dy,Er), with a hitherto unstudied frustrating lattice, the "tripod kagome" structure. Susceptibility (ac, dc) and specific heat exhibit features that are understood within a simple Luttinger-Tisza-type theory. For RE=Gd, we found long-ranged order (LRO) at 1.65 K, which is consistent with a 120° structure, demonstrating the importance of diople interactions for this 2D Heisenberg system. For RE=Dy, LRO at 0.37 K is related to the "kagome spin ice" physics for a 2D system. This result shows that the tripod kagome structure accelerates the transition to LRO predicted for the related pyrochlore systems. For RE=Er, two transitions, at 80 mK and 2.1 K are observed, suggesting the importance of quantum fluctuations for this putative XY system.

Complication and local recurrence rate after endoscopic resection of large high-risk colorectal adenomas of ≥3 cm in size.

PURPOSE: Endoscopic resection is a widely used technique for treatment of large colorectal adenomas, but few data are available including only lesions larger than ≥2 cm. The aim of this study is to evaluate the complication and recurrence rate after endoscopic resection of high-risk colorectal adenomas ≥3 cm in size. METHODS: Retrospective analysis of a prospectively maintained database of patients undergoing polypectomy of large colorectal polyps of ≥3 cm. RESULTS: In 341 patients, 360 colorectal adenomas with a mean size of 3.9 cm were resected endoscopically. In 25 patients, a complication including 22 delayed bleedings (6.5%) and three perforations (0.9%) occurred. Single-variate analysis showed an increasing risk of complications for larger adenomas (3.9 vs. 4.6 cm; p ≤ 0.05). Two hundred twelve patients with 224 adenomas had undergone at least one documented follow-up endoscopy with a medium follow-up period of 16 months. In 95 resected lesions (42.4%), a residual adenoma occurred in the first follow-up colonoscopy (n = 88, 92.6%) or a recurrent adenoma occurred after at least one negative follow-up colonoscopy (n = 7, 7.4%). In multivariate analysis, risk factors were lesion size, sessile growth pattern, and the performing endoscopist. The complication and recurrence rate correlated inversely between endoscopists. CONCLUSIONS: The present study is the largest study showing complication and recurrence rates after colorectal polypectomy of advanced colorectal adenomas of ≥3 cm in size. Polyp size was identified as the most important risk factor for complications. For the first time, this study shows that the complication rate after colorectal polypectomy of large adenomas is correlated inversely with the residual and/or recurrence rate.

Single center experience of endoscopic submucosal dissection (ESD) in early Barrett's adenocarcinoma.

BACKGROUND: Endoscopic mucosal resection (EMR) or radical surgical resection are the standard treatment options for patients with early Barrett's adenocarcinoma (EBAC). Endoscopic submucosal dissection (ESD) is a new endoscopic technique, which allows--in contrast to EMR--endoscopic en-bloc resection of neoplastic lesions greater than 2 cm with complete histological evaluation of the resected specimen. In contrast to Western countries, Barrett's esophagus is less common in Asia indicating the low volume of published data of ESD in EBAC in Japanese series. Therefore, the aim of the present study is to describe the results of ESD in patients with EBAC performed in a German tertiary referral center. METHODS: Between November 2009 and April 2014 ESDs were performed in 22 patients with histologically proven EBAC. Data were given for the en-bloc, the R0, the R0 en-bloc, and the curative resection rate as well as for the complication and the local recurrence rate. RESULTS: ESD was technically possible in all of the 22 patients. 20 of the resected EBAC were mucosal carcinomas, whereas in two patients the tumor showed submucosal invasion. The en-bloc, R0, R0 en-bloc, and curative resection rates were 95.5, 81.8, 81.8 %, and 77.3 %, resp. Complication rate was 27.3 % (perforation n = 1, bleeding n = 2, stenosis n = 3). In case of curative tumor resection, only one local tumor recurrence (5.9 %) occurred after a medium follow-up of 1.6 years. CONCLUSIONS: Despite the small number of patients and a relatively short follow-up, the present data underline the value of ESD, especially in case of curative resections in the definite and less invasive therapy of EBAC. Attention should be drawn toward subsquamous extension of EBAC requiring a sufficient safety margin as an obligate condition for curative R0 resections. Due to the required learning curve and the management of potential complications, ESD should be restricted to greater endoscopic centers.

[Single centre experience of endoscopic submucosal dissection (ESD) in premalignant and malignant gastrointestinal neoplasia]. / Single-Center-Erfahrung mit der Endoskopischen Submukosa-Dissektion (ESD) bei prämalignen und malignen gastrointestinalen Neoplasien.

INTRODUCTION: Worldwide endoscopic submucosal dissection (ESD) of early GI cancers or premalignant neoplasia is becoming increasingly important. In Germany ESD is restricted to larger endoscopic institutions and only a few literature reports are available. The aim of the present study is to describe the results of 46 ESDs conducted in a German endoscopic centre. MATERIAL AND METHODS: Between June 2007 and May 2012 46 ESDs in 45 patients (33 men, 12 women, mean age 66.1 years) were performed in the oesophagus (n = 17), stomach (n = 23) and rectum (n = 6). Data were collected for the en-bloc, R0 and R0 en-bloc resection rates as well as for complications, the curative resection and the local recurrence rates. In order to demonstrate a learning curve, results were evaluated for two periods (June 2007 to November 2010 vs. December 2010 to May 2012). RESULTS: ESD was technically possible in 93.5%. En-bloc, R0, R0 en-bloc and curative resection rates were 90.7%, 74.4%, 67.4% and 65.1%, respectively. The complication rate was 13%. In the second period en-bloc and R0 en-bloc resection rates increased from 81% to 100% and, respectively, from 52.4% to 81.8%. After a medium follow-up of 11.4 months, local tumour recurrence occurred in 10%. In cases of curative R0 en bloc resection of malignant tumours no tumour recurrence occurred. DISCUSSION: Despite the small number of patients, the present data underline the value of ESD, especially in cases of R0 en-bloc resections in the therapy for premalignant and early malignant GI tumours. Due to the required learning curve, ESD should be restricted to larger endoscopic centres in Germany.

Measurement of two low-temperature energy gaps in the electronic structure of antiferromagnetic USb2 using ultrafast optical spectroscopy.

Ultrafast optical spectroscopy is used to study the antiferromagnetic f-electron system USb(2). We observe the opening of two charge gaps at low temperatures (

[New treatment concepts for colonic injury after percutaneous nephrolithotomy]. / Neues Therapiekonzept der Darmverletzung nach perkutaner Nephrolitholapaxie.

Percutaneous nephrolithotomy (PCNL) has become the gold standard for the treatment of large kidney stones > 2 cm and stones in the lower calyces > 1.5 cm. Despite the miniaturization of instruments and the greater expertise of urologists, serious complications can still occur. One of the most dangerous complications is intestinal perforation. Current database analyses report colonic injury in 0.3-0.8% of all cases. These injuries can be treated with either conservative management with long-term drainage and parenteral nutrition, or an exploratory laparotomy with primary closure or creation of a colostomy becomes necessary. We present the case of a 53-year-old woman who underwent left-sided PCNL for a single kidney stone. After removal of the nephrostomy, feces leaked from the puncture channel. After literature research and an interdisciplinary case presentation, the decision was made in favor of an undescribed therapy concept for colon injury after PCNL. After taking laxatives, a colonoscopy was performed. The entry and exit points of the puncture were identified and were both treated with an OTSC® clip (InMedi, Langenhagen, Germany). Immediately after the intervention stool leakage via the puncture channel stopped and the patient was allowed to eat normally. A control sonography on the third day revealed minimal fluid retention in the retroperitoneum which did not require treatment. The patient was then discharged symptom-free.

Mn substitution in the topological metal Zr2Te2P.

Results are reported for Mn intercalated Zr2Te2P, where x-ray diffraction , energy dispersive spectroscopy, and transmission electron microscopy measurements reveal that the van der Waals bonded Te-Te layers are partially filled by Zr and Mn ions. This leads to the chemical formulas Zr0.07Zr2Te2P and Mn0.06Zr0.03Zr2Te2P for the parent and substituted compounds, respectively. The impact of the Mn ions is seen in the anisotropic magnetic susceptibility, where Curie-Weiss fits to the data indicate that the Mn ions are in the divalent state. Heat capacity and electrical transport measurements reveal metallic behavior, but the electronic coefficient of the heat capacity (γMn≈ 36.6 mJ (mol·K2)-1) is enhanced by comparison to that of the parent compound. Magnetic ordering is seen atTM≈4 K, where heat capacity measurements additionally show that the phase transition is broad, likely due to the disordered Mn distribution. This transition also strongly reduces the electronic scattering seen in the normalized electrical resistance. These results show that Mn substitution simultaneously introduces magnetic interactions and tunes the electronic state, which improves prospects for inducing novel behavior in Zr2Te2P and the broader family of ternary tetradymites.

Correlated electron state in Ce(1-x)Yb(x)CoIn5 stabilized by cooperative valence fluctuations.

X-ray diffraction, electrical resistivity, magnetic susceptibility, and specific heat measurements on Ce(1-x)Yb(x)CoIn5 (0≤x≤1) reveal that many of the characteristic features of the x=0 correlated electron state are stable for x≤0.775 and that phase separation occurs for x>0.775. The stability of the correlated electron state is apparently due to cooperative behavior of the Ce and Yb ions, involving their unstable valences. Low-temperature non-Fermi liquid behavior is observed and varies with x, even though there is no readily identifiable quantum critical point. The superconducting critical temperature T(c) decreases linearly with x towards 0 K as x→1, in contrast with other HF superconductors where T(c) scales with T(coh).

Unconventional T-H phase diagram in the noncentrosymmetric compound Yb2Fe12P7.

The temperature-(T-)magnetic-field (H) phase diagram for the noncentrosymmetric compound Yb(2)Fe(12)P(7), [corrected] determined from electrical resistivity (ρ), specific heat (C), and magnetization (M) measurements on single crystal specimens, is reported. This system exhibits a crossover from a magnetically ordered non-Fermi-liquid (NFL) phase at low H to another NFL phase at higher H. The crossover occurs near the value of H where the magnetic ordering temperature (T(M)) is no longer observable in C(T,H)/T and ρ(T,H), but not where T(M) extrapolates smoothly to T=0 K at a possible quantum critical point (QCP). This indicates the occurrence of a quantum phase transition between the two NFL phases. The lack of a clear relationship between the extrapolated QCP and NFL behavior suggests an unconventional route to the NFL ground states.

Electronic and magnetic properties of EuNi2-δ Sb2 structural variants.

X-ray diffraction, magnetic susceptibility, magnetization, heat capacity and electrical resistivity results are reported for single crystals of two structural variants of EuNi2-δ Sb2 that crystallize in the CaBe2Ge2 and ThCr2Si2-type structures. While the former occurs with a stoichiometric ratio, the latter exhibits a Ni site vacancy (δ = 0.36). Both systems exhibit similar magnetic behavior at elevated temperatures, where there is an isotropic Curie-Weiss temperature dependence that indicates an antiferromagnetic exchange interaction between divalent europium ions, although it is stronger for the CaBe2Ge2-variant. At low temperatures, the differing structural environments that surround the Eu ions result in distinct ordering behavior. The CaBe2Ge2-variant orders antiferromagnetically near T N1 = 6.9 K and then undergoes a first order phase transition at T M = 4.6 K. The ThCr2Si2-variant exhibits simpler behavior, with antiferromagnetic ordering at T N2 = 5.6 K. For both compounds, an applied magnetic field suppresses the ordering temperatures and induce metamagnetic phase transitions, while applied pressure causes the ordering temperatures to increase. From these results, EuNi2-δ Sb2 emerges as a useful system in which to study the impact of structural variation on magnetism in a Eu-based metal.

Superconductivity in a uranium containing high entropy alloy.

High entropy alloys (HEA) are an unusual class of materials where mixtures of elements are stochastically arrayed on a simple crystalline lattice. These systems exhibit remarkable functionality, often along several distinct axes: e.g., the examples [TaNb]1-x(TiZrHf)x are high strength and damage resistant refractory metals that also exhibit superconductivity with large upper critical fields. Here we report the discovery of an f-electron containing HEA, [TaNb]0.31(TiUHf)0.69, which is the first to include an actinide ion. Similar to the Zr-analogue, this material crystallizes in a body-centered cubic lattice with the lattice constant a = 3.41(1) Å and exhibits phonon mediated superconductivity with a transition temperatures Tc ≈ 3.2 K and upper critical fields Hc2 ≈ 6.4 T. These results expand this class of materials to include actinide elements, shows that superconductivity is robust in this sub-group, and opens the path towards leveraging HEAs as functional waste forms for a variety of radioisotopes.

A novel cage for actinides: A 6W4Al43 (A = U and Pu).

We report on synthesis and characterization of the compounds A 6W4Al43 (A = U and Pu), that form in the hexagonal Ho6Mo4Al43 caged-structure family. The A ions reside within W/Al cages where the A-A nearest neighbors form dimers between adjacent W/Al cages, with U-U and Pu-Pu distances of 3.3892 [Formula: see text] and 3.4080 [Formula: see text], respectively. While the W/Al networks provide environments similar to those of other cage-like materials (e.g. filled skutterudites), the atomic displacement parameters from single crystal x-ray diffraction measurements show that the A-ions do not exhibit rattling behavior. We find that there is site interchange disorder on one of the W/Al sites. Magnetic susceptibility measurements show that U6W4Al43 displays anisotropic Curie-Weiss behavior where it fits to the data yield an effective magnetic moment near 2.0 [Formula: see text]/U. At low temperatures the magnetic susceptibility deviates from the Curie-Weiss temperature dependence and eventually saturates to a constant value. In contrast, Pu6W4Al43 displays nearly temperature independent Pauli paramagnetism for all temperatures, as would be expected if the 5f -electrons are delocalized. The electrical resistivity for U6W4Al43 increases slightly with the decreasing temperature, suggesting that it is dominated by f -electronic hybridization effects and disorder scattering that originates from the W/Al site interchange. Specific heat measurements for U6W4Al43 further reveal an enhanced electronic Sommerfeld coefficient that is consistent with a moderately enhanced charge carrier effective mass. Together these measurements expose these materials as hosts for unstable f -electron magnetism, where the novel cage-like structures control the phenomena through the spacing between the A ions. Through this combination of mild magnetism, the low cost elements of the Al-W cages, and chemical tunability that has been shown for related materials in the same structure, the A 6W4Al43 compounds emerge as promising nuclear waste-forms for transuranics, while the wider family of materials makes an appealing environment for studying f -electron physics in a novel structure.

Thermodynamic and electrical transport investigation of URu2Si2-x P x.

Magnetic susceptibility, electrical resistivity, and heat capacity results are reported for the chemical substitution series URu2Si2-x P x for [Formula: see text]. This study expands in detail on work recently reported in Gallagher et al (2016 Nat. Commun. 10712), which focused on the small x region of this substitution series. Measurements presented here reveal persistent hybridization between the f- and conduction electrons and strong variation of the low temperature behavior with increasing x. Hidden order and superconductivity are rapidly destroyed for [Formula: see text] and are replaced for [Formula: see text] by a region with Kondo coherence but no ordered state. Antiferromagnetism abruptly appears for [Formula: see text]. This phase diagram differs significantly from those produced by most other tuning strategies in URu2Si2, including applied pressure, high magnetic fields, and isoelectronic chemical substitution (i.e. Ru → Fe and Os), where hidden order and magnetism share a common phase boundary. Besides revealing an intriguing evolution of the low temperature states, this series provides a setting in which to investigate the influence of electronic tuning, where probes that are sensitive to the Fermi surface and the symmetry of the ordered states will be useful to unravel the anomalous behavior of URu2Si2.

Domain engineering of the metastable domains in the 4f-uniaxial-ferromagnet CeRu2Ga2B.

In search of novel, improved materials for magnetic data storage and spintronic devices, compounds that allow a tailoring of magnetic domain shapes and sizes are essential. Good candidates are materials with intrinsic anisotropies or competing interactions, as they are prone to host various domain phases that can be easily and precisely selected by external tuning parameters such as temperature and magnetic field. Here, we utilize vector magnetic fields to visualize directly the magnetic anisotropy in the uniaxial ferromagnet CeRu2Ga2B. We demonstrate a feasible control both globally and locally of domain shapes and sizes by the external field as well as a smooth transition from single stripe to bubble domains, which opens the door to future applications based on magnetic domain tailoring.