Thermo‑magnetic signature of a superconducting multi‑band square with rough surface

In the present work, we will study the efect that the surface roughness of the sample has on the magnetic and thermodynamic properties in a mesoscopic superconducting meso-square under an external magnetic feld in a zero-feld cooling process. We will analyze the magnetization, superconducting electronic density, free Gibbs energy, specifc heat and entropy as a function of the roughness of the sample in a superconducting two-band square taking a Josephson type inter-band coupling. We show that the magnetic and thermodynamic properties depend on the roughness percentage of its surface. Our investigation was carried out by numerically solving the two-band time-dependent Ginzburg–Landau equations

Pontos multicríticos em um modelo para sistemas de elétrons 5f sob pressão e campo magnético

We investigate the evolution of multicritical points under pressure and magnetic field in a model described by two 5f-bands (labeled as and) that hybridize with a single itinerant conduction band. This model is called Underscreened Anderson Lattice Model (UALM). The interaction is given by Coulomb and the Hund’s rule exchange terms, U and J, respectively. We have three cases of study: i) two conventional Spin Density Waves (SDWs) where the magnetic field is applied longitudinally to x-axis for cubic lattice, ii) two conventional SDWs for both cubic and tetragonal lattices when the magnetic field is applied in z-axis and iii) two conventional SDWs and one exotic SDW for cubic lattice when the magnetic field is applied in z-axis. The conventional SDWs, are characterized by AF1 (m f > m f > 0) and AF2 (m f > m f > 0). The exotic SDW or Inter-Orbital Spin Density Wave (IOSDW) is related to a band mixing given by the spin-flip part of the Hund’s rule exchange interaction. As result, without magnetic field, in the cases i) and ii) the phase diagrams of temperature (T) versus pressure (given by the variation of the bandwidth (W)) shows a first-order phase transition between AF1 and AF2 and for the case iii) show a sequence of first-order phase transitions involving the three phases, AF1, IOSDW and AF2L The application of f (magnetic field in x-axis) in the case i) produce the separation of phases AF1 and AF2, acquiring a dome shape that is eventually suppressed for large values of the applied field. For the case ii) we found that Hz (magnetic field in z-axis) favours the phase AF2 while the phase AF1 is suppressed and specifically in the tetragonal lattice, the phase AF2 is even more favored when Hz and c=a increases continuously. For the case iii) the presence of hz (magnetic field in z-axis) has drastic effects on part of the phase diagram and the location of the multicritical points. We propose that the study of multicritical points can provide relevant information on the conventional and unconventional phases present in uranium compoundsInvestigamos a evolução de pontos multicríticos sob pressão e campo magnético em um modelo descrito por duas bandas 5f (chamadas e ) que se hibridizam com uma única banda de condução itinerante. Este modelo chama-se Underscreened Anderson Lattice Model (UALM). A interacção é dada pelos termos de Coulomb e pelo termo de troca da regra de hund, U e J, respectivamente. Temos três casos de estudo: i) duas Spin Denisty Wave (SDWs) convencionais onde o campo magnético é aplicado longitudinalmente ao eixo x em uma rede cúbica, ii) duas SDWs convencionais para as redes cúbica e tetragonal, quando o campo magnético é aplicado no eixo z e iii) duas SDWs convencionais e um SDW exótico em uma rede cúbica quando o campo magnético é aplicado ao longo do eixo z. As fases convencionais SDWs, são caracterizadas por AF1 (m f > m f > 0) e AF2 (m f > m f > 0). O exótico SDW ou Inter-Orbital Spin Density Wave (IOSDW) está relacionada com uma mistura de bandas dada pela parte spin-flip da interacção de troca de regras do Hund Como resultado, sem campo magnético, nos casos i) e ii) os diagramas de fase de temperatura (T) versus pressão (variação da largura de banda (W)) mostram uma transição de fase de primeira ordem entre AF1 e AF2 e para o caso iii) mostram uma sequência de transições de fase de primeira ordem envolvendo as três fases, AF1, IOSDW e AF2. A aplicação de f (campo magnético no eixo x) no caso i) produz a separação das fases AF1 e AF2, adquirindo uma forma de cúpula que é eventualmente suprimida para grandes valores do f . Para o caso ii) descobrimos que Hz (campo magnético no eixo z) favorece a fase AF2 enquanto a fase AF1 é suprimida e especificamente na rede tetragonal, a fase AF2 é ainda mais favorecida quando Hz e c=a aumenta continuamente. Para o caso iii) a presença de hz (campo magnético no eixo z) tem efeitos drásticos sobre parte do diagrama de fase e a localização dos pontos multicríticos. Propomos que o estudo de pontos multicríticos possa fornecer informações relevantes sobre as fases convencionais e não-convencionais presentes nos compostos de urâni

Vortex matter in a two‑band SQUID‑shaped superconducting film

In the present work, we studied the magnetization, vorticity, Cooper pairs density, and the spatial distribution of the local magnetic feld in a three-dimensional super conductor with a SQUID geometry (a square with a central hole connected to the outside vacuum through a very thin slit). Our investigation was carried out in both the Meissner-Ochsenfeld and the Abrikosov state solving the two-band Ginzburg Landau equations considering a Josephson coupling between the bands. We found a non-monotonic vortex behavior and the respective generation of vortex clusters due to the Josephson coupling used between condensates