Two-Fermi-surface superconducting state and a nodal d-wave gap in the electron-doped Sm(1.85)Ce(0.15)CuO(4-d) cuprate superconductor

We report on laser-excited angle-resolved photoemission spectroscopy (ARPES) in the electron-doped cuprate Sm(1.85)Ce(0.15)CuO(4-d). The data show the existence of a nodal hole-pocket Fermi-surface both in the normal and superconducting states. We prove that its origin is long-range antiferromagnetism by an analysis of the coherence factors in the main and folded bands. This coexistence of long-range antiferromagnetism and superconductivity implies that electron-doped cuprates are two-Fermi-surface superconductors. The measured superconducting gap in the nodal hole-pocket is compatible with a d-wave symmetry.Comment: 4 pages, 3 figures, accepted to Phys. Rev. Let

Magnetism, spin texture and in-gap states: Atomic specialization at the surface of oxygen-deficient SrTiO3_3

Motivated by recent spin- and angular-resolved photoemission (SARPES) measurements performed on the two-dimensional electronic states confined near the (001) surface of SrTiO$_3$ in the presence of oxygen vacancies, we explore their spin structure by means of ab initio density functional theory (DFT) calculations of slabs. Relativistic nonmagnetic DFT calculations display Rashba-like spin winding with a splitting of a few meV and when surface magnetism on the Ti ions is in- cluded, bands become spin-split with an energy difference ~100 meV at the $\Gamma$ point, consistent with SARPES findings. While magnetism tends to suppress the effects of the relativistic Rashba interaction, signatures of it are still clearly visible in terms of complex spin textures. Furthermore, we observe an atomic specialization phenomenon, namely, two types of electronic contributions: one is from Ti atoms neighboring the oxygen vacancies that acquire rather large magnetic moments and mostly create in-gap states; another comes from the partly polarized t$_{2g}$ itinerant electrons of Ti atoms lying further away from the oxygen vacancy, which form the two-dimensional electron system and are responsible for the Rashba spin winding and the spin splitting at the Fermi surface.Comment: 6 pages, 4 figures, for Suppl. Mat. please contact first autho

URu2Si2: Trying to understand the mysterious “hidden-order” phase

International audienceDuring the past 30 years the heavy fermion superconductor URu2Si2 has presented a fundamental challenge in condensed matter physics. At T0 = 17.5 K it undergoes a second-order transition from a paramagnetic to a so-called hidden-order (HO) phase, whose order parameter remains elusive despite decades of proposed theoretical models [1–4]. Previous spectroscopic work proved the existence of an electronic instability, producing a Fermi-surface reconstruction and gap opening, across the transition [5-8]. Here we provide new insight into the origin of the HO phase by a direct experimental comparison of its electronic structure with a neighboring low-temperature phase that exhibits well-defined antiferromagnetic (AFM) order, obtained by means of an effective chemical pressure through the partial substitution of Ru with Fe [9]. Our study underlines the key role of hybridization between the heavy fermion and the conduction band states in driving the HO transition, and reveals variations in this interaction across the HO-AFM phase boundary.[1] J. A. Mydosh and P. M. Oppeneer, Rev. Mod. Phys 83, 1301 (2011).[2] P. Chandra, P. Coleman, J. A. Mydosh, and V. Tripathi, Nature 417, 831 (2002).[3] M. B. Maple, J. W. Chen, Y. Dalichaouch, T. Kohara, C. Rossel and M. S. Torikachvilli, Phys. Rev. Lett. 56, 185 (1986).[4] J. A. Mydosh and P. M. Oppeneer, Philos. Mag. 94, 3642 (2014).[5] A. F. Santnder-Syro, M. Klein, F. L. Boariu, A. Nuber, P. Lejay and F. Reinert, Nat. Phys. 5, 637 (2009).[6] A. R. Schmidt, M. H. Hamidian, P. Wahl, F. Meier, A. V. Balatsky, J. D. Garrett, T. J. Williams, G. M. Luke and J. C. Davis, Science 465, 570 (2010).[7] S. Chatterjee, J. Trinckauf, T. Hänke, D. E. Shai, J. W. Harter, T. J. Williams, G. M. Luke, K. M. Shen and J. Geck, Phys. Rev. Lett. 110, 186401 (2013).[8] C. Bareille, F. L. Boariu, H. Schwab, P. Lejay, F. Reinert and A. F. Santander-Syro, Nat. Commun. 5, 4326 (2014).[9] E. Frantzeskakis, J. Dai, T. C. Rödel, M. Güttler, C. Bareille, M. Thees, E. D. L. Rienks, F. Fortuna, M. B. Maple and A. F. Santander-Syro (submitted, 2019)