0705986_Lebed

1. Superconductivity survives at very high magnetic fieldsAndrei G. Lebed, University of Arizona, DMR 0705986 We theoretically study a possibility for superconducting phase to exist in very high magnetic fields. In accordance with the standard quasi-classical Ginzburg-Landau-Abrikosov-Gor’kov and Werthamer-Helfand-Hohenberg theories, superconductivity is destroyed due to the orbital effects at magnetic fields higher than the quasi-classical upper critical field, Hc2(0). We show [1] that, due to quantum effects of electron motion in a magnetic field, superconductivity can exist above Hc2(0). In addition, we investigate [1,2] how superconductivity can survive above another standard theoretical critical field - the so-called Clogston paramagnetic limit, Hp. As a result, we explain experimental phase diagram, recently observed in organic superconductor (TMTSF)2ClO4 (see the figure) by Yonezawa et al. [1] A.G. Lebed, Phys. Rev. Lett. v. 107, p. 087004 (2011). [2] A.G. Lebed and Si Wu, Phys. Rev. B, v. 82, p. 172504 (2010). Experimental superconducting critical field along b’ axis (blue points) exceeds both the quasi-classical upper critical field, Hc2(0) = 3.5T, and the paramagnetic limit, Hp=2.7T, whereas experimental critical field along a axis (red points) exceeds the paramagnetic limit .

2. Superconductivity survives at very high magnetic fields Andrei G. Lebed, University of Arizona, DMR 0705986 Our theoretical research of superconducting phases in high magnetic fields has a broad impact both on the theory and possible applications of superconducting magnets and wires. We predict a unique superconducting phase, where the superconducting temperature grows with growing magnetic field, dTc/dH >0. We call this phase Reentrant Superconductivity (RS) (see the figure). The theoretical understanding of the RS phase can be potentially important for the synthesis new superconducting materials, which are stable in ultra-high magnetic fields and currents and, thus, important for the applications of superconductivity. Our current project serves to train one graduate and one undergraduate student in such vital areas of contemporary physics as superconductivity, correlated electrons, and computational physics. Different possible theoretical scenarios of superconducting phase’s behavior in a magnetic field in a layered superconductor. Scenarios A and B correspond to the appearance of the so-called Reentrant Superconductivity, where superconducting temperature grows in a magnetic field, dTc/dH >0.