| 1. |
- Klein, T., et al.
(author)
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Metal-insulator transition and superconductivity in boron-doped diamond
- 2007
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In: Physical Review B. Condensed Matter and Materials Physics. - 1098-0121 .- 1550-235X. ; 75:165313
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Journal article (peer-reviewed)abstract
- We report on a detailed analysis of the transport properties and superconducting critical temperatures of boron-doped diamond films grown along the {100} direction. The system presents a metal-insulator transition (MIT) for a boron concentration (nB) on the order of nc~4.5×1020 cm−3, in excellent agreement with numerical calculations. The temperature dependence of the conductivity and Hall effect can be well described by variable range hopping for nB<nc with a characteristic hopping temperature T0 strongly reduced due to the proximity of the MIT. All metallic samples (i.e., for nB>nc) present a superconducting transition at low temperature. The zero-temperature conductivity 0 deduced from fits to the data above the critical temperature (Tc) using a classical quantum interference formula scales as 0(nB/nc−1) with ~1. Large Tc values (0.4 K) have been obtained for boron concentration down to nB/nc~1.1 and Tc surprisingly mimics a (nB/nc−1)1/2 law. Those high Tc values can be explained by a slow decrease of the electron-phonon coupling parameter and a corresponding drop of the Coulomb pseudopotential µ* as nBnc.
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| 2. |
- Kacmarcik, J., et al.
(author)
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Unusual Interplay between Superconductivity and Field-Induced Charge Order in YBa2Cu3Oy
- 2018
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In: Physical Review Letters. - 0031-9007 .- 1079-7114. ; 121:16
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Journal article (peer-reviewed)abstract
- We present a detailed study of the temperature (T) and magnetic field (H) dependence of the electronic density of states (DOS) at the Fermi level, as deduced from specific heat and Knight shift measurements in underdoped YBa2Cu3Oy. We find that the DOS becomes field independent above a characteristic field H-DOS, and that the H-DOS (T) line displays an unusual inflection near the onset of the long-range 3D charge-density wave order. The unusual S shape of H-DOS (T) is suggestive of two mutually exclusive orders that eventually establish a form of cooperation in order to coexist at low T. On theoretical grounds, such a collaboration could result from the stabilization of a pair-density wave state, which calls for further investigation in this region of the phase diagram.
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| 3. |
- van der Beek, C. J., et al.
(author)
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Thermodynamics of a heavy-ion-irradiated superconductor : The zero-field transition
- 2007
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In: Physical Review B. Condensed Matter and Materials Physics. - 1098-0121 .- 1550-235X. ; 75:10
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Journal article (peer-reviewed)abstract
- Specific heat measurements show that the introduction of amorphous columnar defects considerably affects the transition from the normal to the superconducting state in zero magnetic field. Experimental results are compared to numerical simulations of the three-dimensional XY model for both the pure system and the system containing random columnar disorder. The numerics reproduce the salient features of experiment, showing in particular that the specific heat peak changes from cusplike to smoothly rounded when columnar defects are added. By considering the specific heat critical exponent alpha, we argue that such behavior is consistent with recent numerical work [A. Vestergren , Phys. Rev. B 70, 054508 (2004)] showing that the introduction of columnar defects changes the universality class of the transition.
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