Dresden 2014 – scientific programme

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TT: Fachverband Tiefe Temperaturen

TT 81: Superconductivity: Properties and Electronic Structure

TT 81.10: Talk

Thursday, April 3, 2014, 12:00–12:15, HSZ 201

Effect of Coulomb Interactions on the Disorder-Driven Superconductor-Insulator Transition — Daniel Sherman^1,2, Uwe S. Pracht¹, Boris Gorshunov^1,3,4, Shachaf Poran², Nandini Trivedi⁵, Pratap Raychaudhuri⁶, Aviad Frydman², and •Martin Dressel¹ — ¹1. Phys. Inst., Universität Stuttgart, Germany — ²Dept. Phys., Bar Ilan Univ., Israel — ³Prokhorov Inst. Gen. Phys., RAS, Moscow, Russia — ⁴Moscow Inst. Phys. Techn., Dolgoprudny, Russia — ⁵Dept. Phys., Ohio State Univ., Columbus, OH, U.S.A. — ⁶Tata Inst. Fund. Res., Mumbai, India

We have studied the evolution of the superconducting energy gap through the disorder-driven superconductor to insulator transition in InO and NbN films using two distinct experimental methods that allow us to test the influence of metallic screening on the electronic interactions. In the case of tunneling spectroscopy a metallic electrode is adjacent to the superconducting film thus screening Coulomb interactions. On the other hand terahertz spectroscopy is a contactless method which probes the sample without affecting the electron-electron interaction. In the presence of screening, a similar superconducting gap is detected on both sides of the superconductor-insulator transition, and at temperatures above and below T_c. Contactless measurements are able to identify the superconducting gap below but not above the critical temperature or in the insulating state. Our study reveals the importance of Coulomb interactions on the energy gap of disordered superconductors.