${}^{11}$B and ${}^{27}$Al NMR spin-lattice relaxation and Knight shift study of Mg${}_{1-x}$Al${}_x$B${}_2$. Evidence for anisotropic Fermi surface

Abstract

We report a detailed study of ${}^{11}$B and ${}^{27}$Al NMR spin-lattice relaxation rates ($1/T_1$), as well as of ${}^{27}$Al Knight shift (K) of Mg${}_{1-x}$Al${}_x$B${}_2$, $0\le x\le 1$. The obtained ($1/T_{1}T$) and K vs. x plots are in excellent agreement with ab initio calculations. This asserts experimentally the prediction that the Fermi surface is highly anisotropic, consisting mainly of hole-type 2-D cylindrical sheets from bonding $2p_{x,y}$ boron orbitals. It is also shown that the density of states at the Fermi level decreases sharply on Al doping and the 2-D sheets collapse at $x\approx 0.55$, where the superconductive phase disappears.

References in corpus (5)

• Effects of Al doping on the structural and electronic properties of Mg(1-x)Al(x)B2
• Crystal structure of the Mg${}_{1-x}$Al${}_x$B${}_2$ superconductors near x=0.5
• Evidence for High-frequency Phonon Mediated S-wave Superconductivity : 11B-NMR Study of Al-doped MgB2
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Cited by in corpus (9)

• Electronic Structure, Electron-Phonon Coupling, and Multiband Effects in MgB2
• Band filling and interband scattering effects in MgB${}_2$: C vs Al doping
• Thermodynamics of Two - Band Superconductors: The Case of MgB${}_2$
• Inversion of two-band superconductivity at the critical electron doping of (Mg,Al)B${}_2$
• NMR relaxation time in a clean two-band superconductor
• Effect of disorder on the NMR relaxation rate in two-band superconductors
• ${}^{11}$B NMR study of pure and lightly carbon doped MgB${}_2$ superconductors
• Is Delta_{pi}-gap-only superconductivity possible in Mg_{1-x}Al_{x}B_{2} and Mg(B_{1-y}C_{y})_{2} alloys?
• Enhancing long-range order in disordered two-band s-wave superconductors