Quantum-well states at the surface of a heavy-fermion superconductor.

Two-dimensional electronic states at surfaces are often observed in simple wide-band metals such as Cu or Ag (refs. 1-4). Confinement by closed geometries at the nanometre scale, such as surface terraces, leads to quantized energy levels formed from the surface band, in stark contrast to the continuous energy dependence of bulk electron bands2,5-10. Their energy-level separation is typically hundreds of meV (refs. 3,6,11). In a distinct class of materials, strong electronic correlations lead to so-called heavy fermions with a strongly reduced bandwidth and exotic bulk ground states12,13. Quantum-well states in two-dimensional heavy fermions (2DHFs) remain, however, notoriously difficult to observe because of their tiny energy separation. Here we use millikelvin scanning tunnelling microscopy (STM) to study atomically flat terraces on U-terminated surfaces of the heavy-fermion superconductor URu2Si2, which exhibits a mysterious hidden-order (HO) state below 17.5 K (ref. 14). We observe 2DHFs made of 5f electrons with an effective mass 17 times the free electron mass. The 2DHFs form quantized states separated by a fraction of a meV and their level width is set by the interaction with correlated bulk states. Edge states on steps between terraces appear along one of the two in-plane directions, suggesting electronic symmetry breaking at the surface. Our results propose a new route to realize quantum-well states in strongly correlated quantum materials and to explore how these connect to the electronic environment.

Influence of Magnetic Ordering between Cr Adatoms on the Yu-Shiba-Rusinov States of the ß-Bi_{2}Pd Superconductor.

We show that the magnetic ordering of coupled atomic dimers on a superconductor is revealed by their intragap spectral features. Chromium atoms on the superconductor ß-Bi_{2}Pd surface display Yu-Shiba-Rusinov bound states, detected as pairs of intragap excitations in tunneling spectra. By means of atomic manipulation with a scanning tunneling microscope's tip, we form Cr dimers with different arrangements and find that their intragap features appear either shifted or split with respect to single atoms. These spectral variations are associated with the magnetic coupling, ferromagnetic or antiferromagnetic, of the dimer, as confirmed by density functional theory simulations. The striking qualitative differences between the observed tunneling spectra prove that intragap Shiba states are extremely sensitive to the magnetic ordering on the atomic scale.

Assessing the impact of palliative care admission of end-of-life cancer adults.

Background: There is evidence that early admission to the palliative care (PC) program in adult cancer patients improves symptoms management, reduces unplanned hospital admissions, minimizes aggressive cancer treatments, and enables patients to make decisions about their end-of-life (EOL) care. Objectives: This retrospective cohort study aimed to determine whether late admission to a PC program is associated with aggressive treatment at the EOL in adult patients with oncological diseases from their admission until death. Design/Methods: The study evaluated the aggressiveness in EOL management in patients with advanced stage oncological diseases who died between 2017 and 2019. The study population was divided into two groups based on the time of admission to the PC program. Aggressiveness at the EOL was measured using five criteria: treatment, hospital admission and duration, emergency department care, and/or intensive care unit utilization. Results: The study found a significant difference in the rate of aggressive EOL treatments between late admission to PC care and early admission [adjusted EOL 79.6% versus 70.4%; relative risk (RR): 1.98, 90% CI: 1.08-3.59, p: 0.061]; In the analysis of secondary variables, a significant association was observed between early admission to PC and the suspension of active treatments at the EOL, leading to a decrease in aggressiveness (77% versus 55.8%; RR: 1.38, 95% CI: 1.14-1.67, p: 0.004). Conclusion: Our findings suggest that early referral to PC services is associated with less aggressive treatment at the EOL, including suspension of active treatments.

Nano-Patterned Magnetic Edges in CrGeTe3 for Quasi 1-D Spintronic Devices.

The synthesis of two-dimensional van der Waals magnets has paved the way for both technological applications and fundamental research on magnetism confined to ultra-small length scales. Edge magnetic moments in ferromagnets are expected to be less magnetized than in the sample interior because of the reduced amount of neighboring ferromagnetic spins at the sample edge. We recently demonstrated that CrGeTe3 (CGT) flakes thinner than 10 nm are hard ferromagnets; i.e., they exhibit an open hysteresis loop. In contrast, thicker flakes exhibit zero net remnant field in the interior, with hard ferromagnetism present only at the cleaved edges. This experimental observation suggests that a nontrivial interaction exists between the sample edge and the interior. Here, we demonstrate that artificial edges fabricated by focus ion beam etching also display hard ferromagnetism. This enables us to write magnetic nanowires in CGT directly and use this method to characterize the magnetic interaction between the interior and edge. The results indicate that the interior saturation and depolarization fields depend on the lateral dimensions of the sample. Most notably, the interior region between the edges of a sample narrower than 300 nm becomes a hard ferromagnet, suggesting an enhancement of the magnetic exchange induced by the proximity of the edges. Last, we find that the CGT regions amorphized by the gallium beam are nonmagnetic, which introduces a novel method to tune the local magnetic properties of CGT films, potentially enabling integration into spintronic devices.

Millikelvin scanning tunneling microscope at 20/22 T with a graphite enabled stick-slip approach and an energy resolution below 8 µeV: Application to conductance quantization at 20 T in single atom point contacts of Al and Au and to the charge density wave of 2H-NbSe2.

We describe a scanning tunneling microscope (STM) that operates at magnetic fields up to 22 T and temperatures down to 80 mK. We discuss the design of the STM head, with an improved coarse approach, the vibration isolation system, and efforts to improve the energy resolution using compact filters for multiple lines. We measure the superconducting gap and Josephson effect in aluminum and show that we can resolve features in the density of states as small as 8 µeV. We measure the quantization of conductance in atomic size contacts and make atomic resolution and density of states images in the layered material 2H-NbSe2. The latter experiments are performed by continuously operating the STM at magnetic fields of 20 T in periods of several days without interruption.

Coherent coupling between vortex bound states and magnetic impurities in 2D layered superconductors.

Bound states in superconductors are expected to exhibit a spatially resolved electron-hole asymmetry which is the hallmark of their quantum nature. This asymmetry manifests as oscillations at the Fermi wavelength, which is usually tiny and thus washed out by thermal broadening or by scattering at defects. Here we demonstrate theoretically and confirm experimentally that, when coupled to magnetic impurities, bound states in a vortex core exhibit an emergent axial electron-hole asymmetry on a much longer scale, set by the coherence length. We study vortices in 2H-NbSe2 and in 2H-NbSe1.8S0.2 with magnetic impurities, characterizing these with detailed Hubbard-corrected density functional calculations. We find that the induced electron-hole imbalance depends on the band character of the superconducting material. Our results show that coupling between quantum bound states in superconductors is remarkably robust and has a strong influence in tunneling measurements.

Simplified feedback control system for scanning tunneling microscopy.

A Scanning Tunneling Microscope (STM) is one of the most important scanning probe tools available to study and manipulate matter at the nanoscale. In a STM, a tip is scanned on top of a surface with a separation of a few Å. Often, the tunneling current between the tip and the sample is maintained constant by modifying the distance between the tip apex and the surface through a feedback mechanism acting on a piezoelectric transducer. This produces very detailed images of the electronic properties of the surface. The feedback mechanism is nearly always made using a digital processing circuit separate from the user computer. Here, we discuss another approach using a computer and data acquisition through the universal serial bus port. We find that it allows successful ultralow noise studies of surfaces at cryogenic temperatures. We show results on different compounds including a type II Weyl semimetal (WTe2), a quasi-two-dimensional dichalcogenide superconductor (2H-NbSe2), a magnetic Weyl semimetal (Co3Sn2S2), and an iron pnictide superconductor (FeSe).

Modelización del tiempo que tarda un paciente con cáncer diferenciado de tiroides en presentar la primera recaída / Modeling of the Time it Takes for a Patient with Differentiated Thyroid Cancer to Present the First Relapse / Modelagem do tempo que um paciente com câncer diferenciado de tireoide leva para apresentar a primeira recidiva

Introducción: de todos los carcinomas de tiroides, los diferenciados son los predominantes. Según la Asociación Colombiana de Endocrinología, la tasa de recaída puede ser de hasta del 30 %, especialmente en pacientes mayores de 45 años y con características tumorales agresivas. En esta investigación se estimó el tiempo libre de enfermedad que transcurre entre la finalización del tratamiento y la ocurren-cia de la primera recaída. Materiales y métodos: se tomó un archivo de datos con los registros de 469 pacientes con cáncer diferenciado de tiroides (cdt) tratados en una clínica especializada de cuarto nivel de complejidad en Bogotá (Colombia). Los datos se recolectaron entre enero de 1997 y diciembre de 2012 y se analizaron estadísticamente usando modelos paramétricos y no paramétricos para obtener las curvas de supervivencia y riesgo. Resultados: con el método no paramétrico se evidenció que en 8.5 años el 75 % de los pacientes no habrán presentado la primera recaída en cdt; mientras que en el método paramétrico el 50 % de los pacientes que no presentaron una tiroglobulina postratamiento menor o igual a 1 ng/mL y un tamaño del tumor menor o igual a 2 cm, su tiempo estimado de la primera recaída fue 29.2 años. Conclusiones: el tiempo libre de enfermedad y el riesgo de hacer recaída para pacientes con cdt está afectado por la presencia de un tamaño de tumor mayor a 2 cm en el momento de la consulta y una cantidad de tiroglobulina mayor a 1 ng/mL, registrada al terminar el tratamiento.

Introduction: Between all thyroid carcinomas, the differentiated are predominant. According to the Colombian Association of Endocrinology, the relapse rate can be up to 30%, especially in patients older than 45 years old and with aggressive tumor characteristics. In this investigation, the time that elapses between the initial surgical treatment and the first relapse of the disease was estimated. Materials and methods: A data file was taken with the records of 469 patients with differentiated thyroid cancer (cdt) treated in a specialized clinic of fourth level of complexity iv in the city of Bogotá (Colombia). Data were collected between January 1997 and December 2012 and were statistically analyzed using para-metric and non-parametric models to obtain survival curves and risk. Results: With the non-parametric method, it is evident that in 8.5 years 75% of the patients will not have presented the first relapse in cdt. While applying the parametric method 50% of patients who do not have a postreatment thyroglobulin or one less than or equal to 1 ng/mL and a tumour size less than or equal to 2 cm, their estimated time of First relapse was 29.2 years. Conclusions: Disease-free time and the risk of relapse for patients with cdt is affected by the presence of a tumor size greater than 2 cm at the time of consultation and levels of thyroglobulin greater than 1 ng/mL, recorded at the end of the treatment.

Introdução: de todos os carcinomas da tireoide, os diferenciados são os predominantes. Segundo a Associação Colombiana de Endocrinologia, a taxa de recaída pode ser até 30%, principalmente em pacien-tes com mais de 45 anos e com características de agressividade tumoral. Nesta investigação, estimou-se o tempo decorrido entre o tratamento cirúrgico inicial e a primeira recaída. Materiais e métodos: tomou-se um arquivo de dados com os prontuários de 469 pacientes com câncer diferenciado de tireoide (cdt) atendidos em uma clínica especializada de quarto nível de complexidade na cidade de Bogotá (Colombia). Coletaram-se os dados entre janeiro de 1997 e dezembro de 2012, que depois foram analisados estatisti-camente usando modelos paramétricos e não paramétricos para encontrar curvas de sobrevida e risco. Resultados: com o método não paramétrico, evidenciou-se que, em 8,5 anos, 75% dos pacientes não terão apresentado a primeira recaída na cdt. Enquanto na aplicação do método paramétrico, 50% dos pacientes que não apresentaram tireoglobulina pós-tratamento ou valores menores ou iguais a 1 ng/mL e tamanho do tumor menor ou igual a 2 cm, seu tempo estimado de primeira recaída foi de 29,2 anos. Conclusões: o tempo livre de doença e o risco de recaída, para pacientes com cdt são afetados pela presença de tama-nho de tumor maior a 2 cm no momento da consulta e uma quantidade de tireoglobulina maior a 1 ng/mL, registrada ao terminar o tratamento.