A cotunneling mechanism for all-electrical Electron Spin Resonance of single adsorbed atoms

The recent development of all-electrical electron spin resonance (ESR) in a scanning tunneling microscope (STM) setup has opened the door to vast applications. Despite the fast growing number of experimental works on STM-ESR, the fundamental principles remains unclear. By using a cotunneling picture, we show that the spin resonance signal can be explained as a time-dependent variation of the tunnel barrier induced by the alternating electric driving field. We demonstrate how this variation translates into the resonant frequency response of the direct current. Our cotunneling theory explains the main experimental findings. Namely, the linear dependence of the Rabi flop rate with the alternating bias amplitude, the absence of resonant response for spin-unpolarized currents, and the weak dependence on the actual atomic species.Comment: 11 pages, 3 figure

Utilizing a single atom magnet and oscillating electric fields to coherently drive magnetic resonance in single atoms

Scanning tunneling microscopes (STM) equipped with pulsed electron spin resonance (ESR) have paved a way to coherently control individual atomic and molecular spins on surfaces. A recent breakthrough was to drive ESR of a spin outside the tunnel junction by locating a single atom magnet in proximity to a qubit, composing a 'spin-magnet pair'. Here we present a combined experimental and model study on the ESR driving mechanism in such a spin-magnet pair. Pulsed ESR of a single hydrogenated Ti atom on MgO with an Fe atom located between 6 and 8 {\AA} away showed a non-vanishing Rabi rate even when the tip is substantially retracted, comparable in strength with that driven by the interaction with the tip's magnetic moment under normal tunnel conditions. We reveal that this ESR driving field is contributed by Fe through the spin-spin interaction in the pair and show its tunability using a vector magnetic field. The spin-magnet pair therefore expands ESR-STM to address and coherently control on-surface atomic and molecular spins independent of the tip's magnetic apex. Together with existing atom manipulation techniques in STM, our study establishes a feasible method to design spin-based multi-qubit systems on surfaces

The Large Observatory For X-ray Timing: LOFT

LOFT, the Large Observatory for X-ray Timing, is a new space mission concept devoted to observations of Galactic and extra-Galactic sources in the X-ray domain with the main goals of probing gravity theory in the very strong field environment of black holes and other compact objects, and investigating the state of matter at supra-nuclear densities in neutron stars. The instruments on-board LOFT, the Large area detector and the Wide Field Monitor combine for the first time an unprecedented large effective area (~10 m2 at 8 keV) sensitive to X-ray photons mainly in the 2-30 keV energy range and a spectral resolution approaching that of CCD-based telescopes (down to 200 eV at 6 keV). LOFT is currently competing for a launch of opportunity in 2022 together with the other M3 mission candidates of the ESA Cosmic Vision Progra

Actas de las V Jornadas ScienCity 2022. Fomento de la Cultura Científica, Tecnológica y de Innovación en Ciudades Inteligentes

ScienCity es una actividad que viene siendo continuada desde 2018 con el objetivo de dar a conocer los conocimientos y tecnologías emergentes siendo investigados en las universidades, informar de experiencias, servicios e iniciativas puestas ya en marcha por instituciones y empresas, llegar hasta decisores políticos que podrían crear sinergias, incentivar la creación de ideas y posibilidades de desarrollo conjuntas, implicar y provocar la participación ciudadana, así como gestar una red internacional multidisciplinar de investigadores que garantice la continuación de futuras ediciones. En 2022 se recibieron un total de 48 trabajos repartidos en 25 ponencias y 24 pósteres pertenecientes a 98 autores de 14 instituciones distintas de España, Portugal, Polonia y Países Bajos.Fundación Española para la Ciencia y la Tecnología-Ministerio de Ciencia, Innovación y Universidades; Consejería de la Presidencia, Administración Pública e Interior de la Junta de Andalucía; Estrategia de Política de Investigación y Transferencia de la Universidad de Huelva; Cátedra de Innovación Social de Aguas de Huelva; Cátedra de la Provincia; Grupo de investigación TEP-192 de Control y Robótica; Centro de Investigación en Tecnología, Energía y Sostenibilidad (CITES

Influence of the Magnetic Tip on Heterodimers in Electron Spin Resonance Combined with Scanning Tunneling Microscopy

Investigating the quantum properties of individual spins adsorbed on surfaces by electron spin resonance combined with scanning tunneling microscopy (ESR-STM) has shown great potential for the development of quantum information technology on the atomic scale. A magnetic tip exhibiting high spin polarization is critical for performing an ESR-STM experiment. While the tip has been conventionally treated as providing a static magnetic field in ESR-STM, it was found that the tip can exhibit bistability, influencing ESR spectra. Ideally, the ESR splitting caused by the magnetic interaction between two spins on a surface should be independent of the tip. However, we found that the measured ESR splitting of a metal atom-molecule heterodimer can be tip-dependent. Detailed theoretical analysis reveals that this tip-dependent ESR splitting is caused by a different interaction energy between the tip and each spin of the heterodimer. Our work provides a comprehensive reference for characterizing tip features in ESR-STM experiments and highlights the importance of employing a proper physical model when describing the ESR tip, in particular, for heterospin systems.11Nsciescopu

Electric‐Field‐Driven Spin Resonance by On‐Surface Exchange Coupling to a Single‐Atom Magnet

Abstract Coherent control of individual atomic and molecular spins on surfaces has recently been demonstrated by using electron spin resonance (ESR) in a scanning tunneling microscope (STM). Here, a combined experimental and modeling study of the ESR of a single hydrogenated Ti atom that is exchange‐coupled to a Fe adatom positioned 0.6–0.8 nm away by means of atom manipulation is presented. Continuous wave and pulsed ESR of the Ti spin show a Rabi rate with two contributions, one from the tip and the other from the Fe, whose spin interactions with Ti are modulated by the radio‐frequency electric field. The Fe contribution is comparable to the tip, as revealed by its dominance when the tip is retracted, and tunable using a vector magnetic field. The new ESR scheme allows on‐surface individual spins to be addressed and coherently controlled without the need for magnetic interaction with a tip. This study establishes a feasible implementation of spin‐based multi‐qubit systems on surfaces

Estudio CRONO: prevalencia del dolor irruptivo en pacientes con dolor crónico no oncológico en Andalucía, España

ABSTRACT Objective: The aim of this study was to evaluate the prevalence of breakthrough pain (BTP) in ambulatory patients with non-cancer chronic pain in Spain and to characterize physiopathology, location, intensity and frequency of BTP episodes. Methods: Prospective, non-interventional, observational study conducted in 16 pain units of hospitals of Andalusia and Ceuta. Eligible consecutive patients were are asked if they experience BTP defined as "a transient exacerbation of pain that occurs either spontaneously, or in relation to a specific predictable or unpredictable trigger, despite stable and controlled background pain". At each survey day, the first two patients reporting BTP were further interrogated on the clinical characteristics of their BTP (etiology, onset, intensity, frequency and treatment). Results: A total of 3,209 patients with non-cancer chronic pain were screened to identify 1,118 patients with BTP, which represented a prevalence of 36 %. BTP characteristics were retrieved from 350 patients: mean BTP intensity was 8.3 (± 1.4) on a Visual Analogue Scale (VAS), with a mean of 2 episodes/24 hour (range 1-5/24 h). Pain mechanism was mixed in 149 (42.6 %), neuropathic in 91 (26 %) and nociceptive in 72 in (20.6 %) of patients. Significant correlation was found between BTP intensity and both higher background pain (r = 0.243, p < 0.001), and daily BTP episodes frequency (r = 0.123, p = 0.003). 78 % of the patients were on opioid treatment. The most frequent were fentanyl citrate (52.6 %) and tramadol (17.4 %). Conclusions: The prevalence rate of BTP in patients with chronic non-oncologic pain is higher than one-third of the patients seen in outpatient hospital pain units in Spain. BTP causes reduced levels of functionality, psychological disorders, and an increase in health care expenditure. Individualization is the key to treatment.RESUMEN Objetivo: El objetivo de este estudio es evaluar la prevalencia de dolor irruptivo (DI) en pacientes ambulatorios con dolor crónico de origen no oncológico y caracterizar la fisiopatología, localización, intensidad y frecuencia de los episodios de DI. Material y métodos: Estudio observacional, prospectivo y no intervencionista realizado en 16 unidades de dolor ambulatorias de hospitales de Andalucía y Ceuta. Se preguntó a los pacientes consecutivos elegibles si experimentan DI definido como "una exacerbación transitoria del dolor que ocurre espontáneamente, o en relación con un desencadenante predecible o impredecible específico, a pesar del dolor de base estable y controlado". En cada día de la encuesta, los dos primeros pacientes que confirmaron DI fueron preguntados sobre las características clínicas de su PTP (etiología, inicio, intensidad, frecuencia y tratamiento). Resultados: Se realizó un cribaje a un total de 3209 pacientes con dolor crónico no oncológico para identificar a 1118 pacientes con DI, lo que representó una prevalencia del 36 %. Se obtuvieron las características del DI de 350 pacientes: la intensidad media fue de 8,3 (± 1,4) en una Escala Analógica Visual (EVA), con una media de 2 episodios/24 horas (rango 1-5/24 h). El mecanismo del dolor fue mixto en 149 (42,6 %), neuropático en 91 (26 %) y nociceptivo en 72 (20,6 %) de los pacientes. Se encontró correlación positiva entre una mayor intensidad de DI con el nivel de dolor basal (r = 0,243, p < 0,001), y el número de crisis diarias de DI (r = 0,123, p = 0,003), ambas estadísticamente significativas. El 78 % de los pacientes estaba en tratamiento con opioides. Los más frecuentes fueron el citrato de fentanilo (52,6 %) y el tramadol (17,4 %). Conclusiones: La tasa de prevalencia del DI en pacientes con dolor crónico no oncológico es superior a un tercio de los pacientes atendidos en las unidades ambulatorias de dolor hospitalario en España. El DI provoca niveles reducidos de funcionalidad, trastornos psicológicos y un aumento del gasto asistencial. La clave del tratamiento es la individualización