Doping dependence of the Nernst effect in Eu(Fe1-xCox)2As2 - departure from Dirac fermions physics

We report a systematic study of the transport properties in the series of Eu(Fe1-xCox)2As2 single crystals with x = 0, 0.15, 0.20 and 0.30. Spin-density-wave order is observed in the undoped and the least doped samples (x = 0, 0.15), while for x = 0.15 and 0.20 Eu(Fe1-xCox)2As2 becomes a superconductor. We found the properties of the parent EuFe2As2 compound well described by the Dirac fermions model, whereas cobalt doping caused an evolution of the system toward a regular metallic state. The antiferromagnetic ordering of the Eu2+ ions at T_N ~ 20 K has only minor influence on the measured quantities.Comment: 5 pages, 5 figures; ver.3: the sign convention for the Nernst coefficient is change

Recenzja

Jacek Woźny, Symbolika przestrzeni miejsc grzebalnych w czasach ciałopalenia zwłok na ziemiach polskich (od środkowej epoki brązu do środkowego okresu lateńskiego), Bydgoszcz 2000, ss. 187

Opiniowanie miejscowych planów zagospodarowania przestrzennego przez wojewódzkich inspektorów ochrony środowiska w związku z lokalizacją zakładów zagrożonych poważną awarią

The article deals with the issuing of opinions on local spatial development plans by the voivodeship environmental protection inspector in connection with the location of plants at risk of a serious accident. The article analyses in detail the regulations in the aforementioned field. The following conclusions were adopted: 1. Not in every case is the local spatial development plan referred to the voivode-ship environmental protection inspector for an opinion; 2. after the commune council adopts a resolution to begin drawing up the local plan, it is the commune head, mayor or city president that decides to apply to the voivodeship environmental protection inspector for an opinion on the draft plan, provided that the plan allows the location of plants posing a risk of a serious in-dustrial accident; 3. should the head of the commune, mayor or president not request that the voivodship environmental protection inspector issue an opinion on the draft plan, this will constitute a violation of the plan preparation procedure if the plan allows the location of plants posing the risk of a serious industrial accident; 4. issues related to the deadline for giving an opinion and its extension are regu-lated in the Act on Spatial planning and development, which regulations constitute a lex specialis to the Code of Administrative Procedure; 5. any failure by the commune head, mayor, city president to take into account the negative opinion of the voivodeship environmental protection inspector, based on specific regulations concerning the location of plants posing the risk of a serious industrial accident, is a violation of the law

Organy ochrony środowiska: administracja rządowa ochrony środowiska

Zagadnienie systemowe prawa ochrony środowiska, którym została poświęcona książka, ma wielkie teoretyczne i praktyczne znaczenie w dogmatyce prawa. Rozważania, które wypełniają treść książki, dotyczą wybranych zagadnień prawa ochrony środowiska, tworząc w ten sposób pewien zarys systemowego ujęcia tej gałęzi prawa. Przedmiot badanej problematyki potraktowany zostało przez Autorów w sposób otwarty na zainteresowania i potrzeby przedstawicieli innych dziedzin prawoznawstwa. Ważną częścią składową problemu doskonalenia modelu prawnego ochrony środowiska jest lepsze wykorzystanie instrumentów prawnych pozwalających racjonalnie połączyć różne metody regulacji prawnej w system prawa. Budowanie mechanizmu ochrony prawnej środowiska jest oczywiście zadaniem wielowymiarowym i wymaga kompleksowego doń podejścia z uwzględnieniem szerokiej analizy systemowej najważniejszych zagadnień z tej dziedziny. Książka poświęcona jest teoretycznemu opracowaniu wybranych zagadnień systemowych prawa ochrony środowiska. Nie obejmuje ona wszystkich stron przedstawionego problemu, co oczywiście trudno jest dokonać w jednej pracy. Koncepcji zagadnień systemowych prawa ochrony środowiska, wysuwanej w pracy, nie można uważać za bezsporną, ale jest ona poważnie uargumentowana i daje asumpt do poważnych przemyśleń. Oddając w ręce Czytelnika tę książkę, żywimy nadzieję, że wypełni ona istotną lukę w piśmiennictwie dotyczącym analizy systemowej prawa ochrony środowiska. Książka jest pierwszą monografią w serii „Biblioteka Problemów Prawa Ochrony Środowiska”, w ramach którego będą prezentowane poglądy przedstawicieli doktryny oraz praktyków zajmujących stosowaniem prawa ochrony środowiska.Publikacja dofinansowana ze środków Wojewódzkiego Funduszu Ochrony Środowiska i Gospodarki Wodnej w Łodzi oraz Wydziału Prawa i Administracji Uniwersytetu Łódzkiego

Re-entrance of resistivity due to the interplay of superconductivity and magnetism in \ce{Eu_{0.73}Ca_{0.27}(Fe_{0.87}Co_{0.13})2As2}

By simultaneous Co and Ca-doping we were able to obtain an \ce{EuFe2As2}-based compound with superconductivity appearing above the antiferromagnetic order of \ce{Eu^{2+}} magnetic moments. However, as soon as the antiferromagnetic order appears a re-entrance behavior is observed \textemdash{} instead of zero resistivity and diamagnetic signal down to the temperature of \unit[2]{K}. By investigating magnetization, ac susceptibility and electrical transport properties of \ce{Eu_{0.73}Ca_{0.27}(Fe_{0.87}Co_{0.13})2As2} and comparing them to previously studied M\"ossbauer effect and neutron scattering measurements of this and similar compounds an explanation of such behavior is proposed.Comment: Main paper of 9 pages with 9 figures with Supplementary Material

Electronic band structure and surface states in Dirac semimetal LaAgSb2LaAgSb_{2}

LaAgSb$_{2}$ is a Dirac semimetal showing charge density wave (CDW) order. Previous angle-resolved photoemission spectroscopy (ARPES) results suggest the existence of the Dirac-cone-like structure in the vicinity of the Fermi level along the $\Gamma$–M direction. This paper is devoted to a complex analysis of the electronic band structure of LaAgSb$_{2}$ by means of ARPES and theoretical studies within the ab initio method as well as tight binding model formulation. To investigate the possible surface states, we performed the direct DFT slab calculation and the surface Green function calculation for the (001) surface. The appearance of the surface states, which depends strongly on the surface, points to the conclusion that LaSb termination is realized in the cleaved crystals. Moreover, the surface states predicted by our calculations at the $\Gamma$ and X points are found by ARPES. Nodal lines, which exist along the X–R and M–A paths due to crystal symmetry, are also observed experimentally. The calculations reveal other nodal lines, which originate from the vanishing of spin–orbit splitting and are located at the X–M–A–R plane at the Brillouin zone boundary. In addition, we analyze the band structure along the $\Gamma$–M path to verify whether Dirac surface states can be expected. Their appearance in this region is not confirmed

Direct evidence for the emergence of a pressure induced nodal superconducting gap in the iron-based superconductor Ba_0.65Rb_0.35Fe_2As_2

Identifying the superconducting (SC) gap structure of the iron-based high-temperature superconductors (Fe-HTS's) remains a key issue for the understanding of superconductivity in these materials. In contrast to other unconventional superconductors, in the Fe-HTS's both $d$-wave and extended s-wave pairing symmetries are close in energy, with the latter believed to be generally favored over the former. Probing the proximity between these very different SC states and identifying experimental parameters that can tune them, are of central interest. Here we report high-pressure muon spin rotation experiments on the temperature-dependent magnetic penetration depth (lambda) in the optimally doped Fe-HTS Ba_0.65Rb_0.35Fe_2As_2. At ambient pressure this material is known to be a nodeless s-wave superconductor. Upon pressure a strong decrease of (lambda) is observed, while the SC transition temperature remains nearly constant. More importantly, the low-temperature behavior of (1/lambda^{2}) changes from exponential saturation at zero pressure to a power-law with increasing pressure, providing unambiguous evidence that hydrostatic pressure promotes nodal SC gaps. Comparison to microscopic models favors a d-wave over a nodal s^{+-}-wave pairing as the origin of the nodes. Our results provide a new route of understanding the complex topology of the SC gap in Fe-HTS's.Comment: 33 pages and 12 figures (including supplementary information

Structural and Superconducting Properties of RbOs2O6 Single Crystals

Single crystals of RbOs2O6 have been grown from Rb2O and Os in sealed quartz ampoules. The crystal structure has been identified at room temperature as cubic with the lattice constant a = 10.1242(12) A. The anisotropy of the tetrahedral and octahedral networks is lower and the displacement parameters of alkali metal atoms are smaller than for KOs2O6, so the "rattling" of the alkali atoms in RbOs2O6 is less pronounced. Superconducting properties of RbOs2O6 in the mixed state have been well described within the London approach and the Ginzburg-Landau parameter kappa(0) = 31 has been derived from the reversible magnetization. This parameter is field dependent and changes at low temperatures from kappa = 22 (low fields) to kappa = 31 at H_{c2}. The thermodynamic critical field H_{c}(0) = 1.3 kOe and the superconducting gap 2delta/k_{B}T_{c} = 3.2 have been estimated. These results together with slightly different H_{c2}(T) dependence obtained for crystals and polycrystalline RbOs2O6 proof evidently that this compound is a weak-coupling BCS-type superconductor close to the dirty limit.Comment: 20 pages, 8 figures, 3 table