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We calculate RPA-BCS based spin resonance spectra of newly discovered iron-selenide superconductor using two orbitals tight-binding (TB) model. The slightly squarish electron pocket Fermi surfaces (FSs) at $(\pi,0)/(0,\pi)-$momenta produce…

Superconductivity · Physics 2011-08-02 Tanmoy Das , A. V. Balatsky

To determine the superconducting gap function of a borocarbide superconductor YNi_2B_2C, the c-axis thermal conductivity kappa_zz was measured in a magnetic field rotated in various directions relative to the crystal axes. The angular…

Superconductivity · Physics 2009-03-24 K. Izawa , K. Kamata , Y. Nakajima , Y. Matsuda , T. Watanabe , M. Nohara , H. Takagi , P. Thalmeier , K. Maki

The thermal conductivity of borocarbide superconductor LuNi_2B_2C was measured down to 70 mK (T_c/200) in a magnetic field perpendicular to the heat current from H = 0 to above H_c2 = 7 T. As soon as vortices enter the sample, the…

Superconductivity · Physics 2009-11-07 Etienne Boaknin , R. W. Hill , Cyril Proust , C. Lupien , Louis Taillefer , P. C. Canfield

The recent discovery of superconductivity in iron-arsenic compounds below a transition temperature (Tc) as high as 55K ended the monopoly of copper oxides (cuprates) in the family of high-Tc superconductors. A critical issue in…

Quasi-two-dimensional molecular conductor $\lambda$-(BETS)$_2$GaCl$_4$ shows superconductivity (SC) below 5.5K, neighboring the dimer-type Mott insulating phase. To elucidate the origin of SC and its gap function, we carry out…

Superconductivity · Physics 2018-08-01 Hirohito Aizawa , Takashi Koretsune , Kazuhiko Kuroki , Hitoshi Seo

We present scanning tunneling spectroscopy and microscopy measurements at low temperatures in the borocarbide materials RNi2B2C (R=Y, Lu). The characteristic strong coupling structure due to the pairing interaction is unambiguously resolved…

Superconductivity · Physics 2009-11-07 P. Martinez-Samper , H. Suderow , S. Vieira , J. P. Brison , N. Luchier , P. Lejay , P. C. Canfield

We report measurements of the momentum dependence of the superconducting gap in Bi_2Sr_2CaCu_2O_{8+x} (Bi2212) with angle-resolved photoemission spectroscopy using a dense sampling of the Brillouin zone in the vicinity of the Fermi surface.…

We performed high-resolution angle-resolved photoemission spectroscopy on electron-doped high-Tc superconductor Pr0.89LaCe0.11CuO4 to study the anisotropy of the superconducting gap. The observed momentum dependence is basically consistent…

Superconductivity · Physics 2009-11-10 H. Matsui , K. Terashima , T. Sato , T. Takahashi , M. Fujita , K. Yamada

It is shown within the weak-coupling model that the macroscopic superconducting anisotropy for materials with the gap varying on the Fermi surface cannot be characterized by a single number, unlike the case of clean materials with isotropic…

Superconductivity · Physics 2009-11-07 V. G. Kogan

Borocarbide superconductors, which are thought to be conventional BCS-type superconductors, are not so conventional in several electronic Raman properties. Anisotropic gap-like features and finite scattering strength below the gap were…

Superconductivity · Physics 2015-06-25 In-Sang Yang , M. V. Klein , T. P. Devereaux , I. R. Fisher , P. C. Canfield

We performed a high-resolution angle-resolved photoemission spectroscopy study on superconducting (SC) Tl$_{0.63}$K$_{0.37}$Fe$_{1.78}$Se$_2$ ($T_c=29$ K) in the whole Brillouin zone (BZ). In addition to a nearly isotropic $\sim$ 8.2 meV…

The nature and symmetry of the superconducting gap function in the noncentrosymmetric superconductor (NCS) Li2Pt3B, even many years after its discovery, appears to be full of contradictions. In this letter based on the existing band…

Superconductivity · Physics 2015-05-30 Soumya P. Mukherjee , Tetsuya Takimoto

The thermal conductivity k of the iron-arsenide superconductor Ba(Fe_{1-x}Co_x)_2As_2 was measured down to 50 mK for a heat current parallel (k_c) and perpendicular (k_a) to the tetragonal c axis, for seven Co concentrations from underdoped…

It is shown theoretically that the Sommerfeld coefficient $\gamma(B)$ in the mixed state contains useful information on the gap topology in a superconductor. We accurately evaluate $\gamma(B)$ against magnetic induction $B$ by using…

Superconductivity · Physics 2016-08-16 N. Nakai , P. Miranović , M. Ichioka , K. Machida

We present measurements of the superconducting gap of URu$_2$Si$_2$ made with scanning tunneling microscopy (STM) using a superconducting tip of Al. We find tunneling conductance curves with a finite value at the Fermi level. The density of…

Superconductivity · Physics 2015-06-03 A. Maldonado , I. Guillamon , J. G. Rodrigo , H. Suderow , S. Vieira , D. Aoki , J. Flouquet

We present a study of the anisotropy in the superconducting energy gap in a single crystal of YNi2B2C (Tc~14.6K) using directional point contact spectroscopy. The superconducting energy gap at 2.7K, when measured for I||c, is 4.5 times…

Superconductivity · Physics 2007-05-23 P. Raychaudhuri , D. Jaiswal-Nagar , Goutam Sheet , S. Ramakrishnan , H. Takeya

The symmetry and structure of the superconducting gap in the Fe-based superconductors are the central issue for understanding these novel materials. So far the experimental data and theoretical models have been highly controversial. Some…

Superconductivity · Physics 2011-09-13 B. Zeng , G. Mu , H. Q. Luo , T. Xiang , H. Yang , L. Shan , C. Ren , I. I. Mazin , P. C. Dai , H. -H. Wen

The differential resistances $R_d=dV/dI(V)$ of point contacts between a normal metal and a c axis oriented YNi2B2C film ($T_c$ = 15.2K) in the superconducting (SC) state have been investigated. $R_d(V)$ contains clear "gap" features…

Superconductivity · Physics 2009-11-11 D. L. Bashlakov , Yu. G. Naidyuk , I. K. Yanson , S. C. Wimbush , B. Holzapfel , G. Fuchs , S. -L. Drechsler

We use high resolution angle resolved photoemission spectroscopy and density functional theory with experimentally obtained crystal structure parameters to study the electronic properties of CaKFe4As4. In contrast to related CaFe2As2…

Although nodeless superconducting gap has been observed on the large Fermi pockets around the zone corner in KxFe2-ySe2, whether its pairing symmetry is s-wave or nodeless d-wave is still under intense debate. Here we report an isotropic…

Superconductivity · Physics 2012-06-25 M. Xu , Q. Q. Ge , R. Peng , Z. R. Ye , Juan Jiang , F. Chen , X. P. Shen , B. P. Xie , Y. Zhang , D. L. Feng