Thermopower and thermal conductivity in the Weyl semimetal NbP

The Weyl semimetal NbP exhibits an extremely large magnetoresistance (MR) and an ultra-high mobility. The large MR originates from a combination of the nearly perfect compensation between electron- and hole-type charge carriers and the high mobility, which is relevant to the topological band structure. In this work we report on temperature- and field-dependent thermopower and thermal conductivity experiments on NbP. Additionally, we carried out complementary heat capacity, magnetization, and electrical resistivity measurements. We found a giant adiabatic magnetothermopower with a maximum of 800 $\mu$V/K at 50 K in a field of 9 T. Such large effects have been observed rarely in bulk materials. We suggest that the origin of this effect might be related to the high charge-carrier mobility. We further observe pronounced quantum oscillations in both thermal conductivity and thermopower. The obtained frequencies compare well with our heat capacity and magnetization data.Comment: 6 pages, 3 figure

Adsorptive properties and on-demand magnetic response of lignin@Fe3O4 nanoparticles at castor oil–water interfaces

Lignin@Fe3O4 nanoparticles adsorb at oil–water interfaces, form Pickering emulsions, induce on-demand magnetic responses to break emulsions, and can sequester oil from water. Lignin@Fe3O4 nanoparticles were prepared using a pH-induced precipitation method and were fully characterized. These were used to prepare Pickering emulsions with castor oil/Sudan red G dye and water at various oil/water volume ratios and nanoparticle concentrations. The stability and demulsification of the emulsions under different magnetic fields generated with permanent magnets (0–540 mT) were investigated using microscopy images and by visual inspection over time. The results showed that the Pickering emulsions were more stable at the castor oil/water ratio of 50/50 and above. Increasing the concentration of lignin@Fe3O4 improved the emulsion stability and demulsification rates with 540 mT applied magnetic field strength. The adsorption of lignin@Fe3O4 nanoparticles at the oil/water interface using 1-pentanol evaporation through Marangoni effects was demonstrated, and magnetic manipulation of a lignin@Fe3O4 stabilized castor oil spill in water was shown. Nanoparticle concentration and applied magnetic field strengths were analyzed for the recovery of spilled oil from water; it was observed that increasing the magnetic strength increased oil spill motion for a lignin@Fe3O4 concentration of up to 0.8 mg mL−1 at 540 mT. Overall, this study demonstrates the potential of lignin-magnetite nanocomposites for rapid on-demand magnetic responses to externally induced stimuli

Extremely high conductivity observed in the triple point topological metal MoP

Weyl and Dirac fermions have created much attention in condensed matter physics and materials science. Recently, several additional distinct types of fermions have been predicted. Here, we report ultra-high electrical conductivity in MoP at low temperature, which has recently been established as a triple point Fermion material. Here we show that the electrical resistivity is 6 n-ohm cm at 2 K with a large mean free path of 11 microns. de Haas-van Alphen oscillations reveal spin splitting of the Fermi surfaces. In contrast to noble metals with similar conductivity and number of carriers, the magnetoresistance in MoP does not saturate up to 9 T at 2 K. Interestingly, the momentum relaxing time of the electrons is found to be more than 15 times larger than the quantum coherence time. This difference between the scattering scales shows that momentum conserving scattering dominates in MoP at low temperatures.Comment: Updated texts and supplementar

A semblance of the first Spanish women pioneers in the scientific-technical area

[EN] Although the Spanish Consejo Superior de Investigaciones Científicas focuses its research on eight major scientific-technical areas, which cover most of human knowledge, from the most basic or fundamental aspects of science to the most complex technological developments; from human and social sciences to food science and technology through Biology, Biomedicine, Physics, Chemistry, Materials, natural resources or agricultural sciences, the disciplines that have traditionally been considered to constitute this area are Mathematics, Physics, Chemistry, Biology, Architecture and Engineering. This communication shows a brief semblance of Spanish women who can be considered pioneers, because they are the first graduates or the first Ph.D. doctors, in each of these disciplines. The objective is that society in general, for which almost certainly these women are practically unknown, can take them as a reference and an example of what women are capable of doing in any field of life, even though they have to overcome many difficulties of all kinds, of gender, fundamentally, to achieve their purposes and also to succeed in fields that originally seem to be destined only for males.[ES] Aunque el Consejo Superior de Investigaciones Científicas centra su investigación en torno a ocho grandes áreas científico-técnicas, que cubren la mayor parte del conocimiento humano, desde los aspectos más básicos o fundamentales de la ciencia hasta los desarrollos tecnológicos más complejos; desde las ciencias humanas y sociales a la ciencia y tecnología de alimentos pasando por la Biología, la Biomedicina, la Física, la Química, los materiales, los recursos naturales o las ciencias agrarias, tradicionalmente se ha considerado que las disciplinas que conforman este área de conocimiento son Matemáticas, Física, Química, Biología, Arquitectura e Ingeniería. En este artículo se muestra una breve semblanza de las mujeres españolas que pueden considerarse pioneras, por ser las primeras licenciadas o las primeras doctoras, en cada una de esas disciplinas. El objetivo es que la sociedad en general, para la que casi con toda seguridad estas mujeres son prácticamente desconocidas, pueda tomarlas como referente y ejemplo de lo que las mujeres son capaces de hacer en cualquier estamento de la vida, aun teniendo que superar numerosas dificultades de todo tipo, de género, fundamentalmente, para lograr sus propósitos y también conseguir triunfar en campos que originariamente parecen estar destinados solo a los varones.Núñez Valdés, J. (2019). Una semblanza de las primeras mujeres españolas pioneras en el área científico-técnica. Ciencia, Técnica y Mainstreaming Social. (3):34-44. https://doi.org/10.4995/citecma.2019.11142SWORD34443Algora Alba, Carlos (1996). El Instituto-Escuela de Sevilla (1932-36), Diputación de Sevilla, sección Ciencias Sociales, número 7.Araque, Natividad (2008): "Jenara Vicenta Arnal Yarza: una científica y catedrática pionera en España" en Faísca: Revista de altas capacidades, 14, 16, 27-49.Araque, Natividad, Villa, Núria (2011): "La labor de las primeras directoras de los Institutos de Enseñanza Media de Madrid: Beatriz Galindo y Emperatriz María de Austria" en Participación Educativa, número extraordinario, 225-239Carbonell, Carmen y Núñez, Juan (2010): "100 a-os de derechos: la primera mujer española doctora en Física". En II Congreso Universitario Nacional Investigación y Género. Universidad de Sevilla, 781 - 792.Durán, María José, Escudero, Ana María, Núñez, Juan y Regodón, Elena (2011): "La arquitectura, un lugar para las mujeres". En III Congreso Universitario Nacional Investigación y Género. Universidad de Sevilla, 1392 - 1407.Flecha García, Consuelo (1996): Las primeras universitarias en España, 1872-1910. Narcea Ediciones, 1996. 264 páginas.Gómez, L., Núñez, Juan, Ramos, A. (2016): "Un paseo por la vida de las primeras mujeres biólogas en España". En III International Conference Gender and Communication y I Congreso de Micromachismo en la Comunicación, Facultad de Comunicación. Universidad de Sevilla. 7 y 8 de abril, 2016.González-Martín, Francisco Javier (2013): "Pilar Careaga y Basabe (1908-1993): Feminismo católico y militancia política en el franquismo" en Aportes, 81, a-o XXVIII, 159-189.Magallón-Portolés, Carmen (1997): "Mujeres en las ciencias físico-químicas en España: el Instituto Nacional de Ciencias y el Instituto Nacional de Física y Química (1910-1936)" en Llull, 20, 39, 529. AAAMagallón Portolés, Carmen (1998): Pioneras españolas en la ciencia. Las mujeres del Instituto Nacional de Física y Química. Consejo Superior de Investigaciones Científicas.Magallón-Portolés, Carmen (1991): "La incorporación de las mujeres a las carreras científicas en la España Contemporánea: la Facultad de Ciencias de Zaragoza (1882-1936)" en Llull, 14, 27, 531-549.Magallón-Portolés, Carmen (2001): "La residencia de estudiantes para señoritas y el laboratorio Foster (Mujeres de ciencia en España a principios del siglo XX)", en Endoxa: Series Filosóficas, n." 14, 157-181.Maraver, Rocío, Núñez, Juan. (2009): "Carmen Martínez Sancho y el Instituto Murillo de Sevilla: una relación de entrega y generosidad". En I Congreso Universitario Andaluz Investigación y Género. Universidad de Sevilla, 17 y 18 de junio de 2009, 883-893.Núñez, Juan., Rodríguez-Antón, B., Rodríguez-Remesal, E. (2014a): "Primeras mujeres doctoras en Química en España". En V Congreso Universitario Nacional Investigación y Género. Universidad de Sevilla, 21 y 22 de junio de 2012, 1287-1298.Núñez, Juan., Alonso, Alejandro y Arroyo, María (2014b). "Primeras mujeres licenciadas en Farmacia en España" V Congreso Universitario Nacional Investigación y Género. Universidad de Sevilla, 03 y 04 de Julio de 2014, página 5.Sánchez-Ron, José Manuel (2014): Conversación de Margarita Salas y José Manuel Sánchez Ron. Mercurio. Fundación José Manuel Lara. La ciencia en la Academia.Torreira, M., Núñez, Juan. (2018): "Pilar Careaga, mujer adelantada a su época". En IV International Conference on Gender and Communication, Sevilla, 7 y 9 de marzo de 2018, página 8

Giant anomalous Nernst signal in the antiferromagnet YbMnBi₂

A large anomalous Nernst effect (ANE) is crucial for thermoelectric energy conversion applications because the associated unique transverse geometry facilitates module fabrication. Topological ferromagnets with large Berry curvatures show large AN Es; however, they face drawbacks such as strong magnetic disturbances and low mobility due to high magnetization. Herein, we demonstrate that YbMnBi2, a canted antiferromagnet, has a large ANE conductivity of similar to 10 A m(-1) K-1 that surpasses large values observed in other ferromagnets (3-5 A m(-1) K-1). The canted spin structure of Mn guarantees a non-zero Berry curvature, but generates only a weak magnetization three orders of magnitude lower than that of general ferromagnets. The heavy Bi with a large spin-orbit coupling enables a large ANE and low thermal conductivity, whereas its highly dispersive P-x/y orbitals ensure low resistivity. The high anomalous transverse thermoelectric performance and extremely small magnetization make YbMnBi2 an excellent candidate for transverse thermoelectrics