Structural Tuning of Unconventional Superconductivity inPuMGa5(M=

E. D. Bauer

¹

,

J. D. Thompson

²

,

J. L. Sarrao

³

et al.

Abstract

The superconducting properties of the recently discovered PuMGa5 (M=Co,Rh) superconductors, including the power law behavior of the specific heat, the evolution of the superconducting transition T(c) temperature with pressure, and the linear relation between T(c) and ratio of tetragonal lattice parameters c/a, are compared to those of the heavy fermion CeMIn5 (M=Co,Rh,Ir) unconventional superconductors. The striking similarity of the properties between the two families of superconductors suggests a common physics and a common (magnetically mediated) mechanism of superconductivity.

Unconventional superconductivity in PuCoGa5

“…Two-dimensional (2D) optical spectroscopy 3,8,[17][18][19][20][21] measures the full nonlinear polarization of a quantum system in third order with respect to the field-matter interaction 3,8,22 . A sequence of three ultrashort laser pulses excites the sample, and the emitted phasematched signal field is detected in amplitude and phase as a function of optical frequency and the three experimentally controlled excitation-pulse time delays t, T and t. Fourier transforms of the data 8,21 reveal complex-valued 2D (q t , q t ) frequency maps of the system's response, where q t and q t are the conjugate Fourier frequencies of t and t. The real part can be interpreted as the transient field amplitude at a particular probe frequency q t , induced by a specific excitation frequency q t , after the waiting time (population time) T. The imaginary part describes transient changes in the refractive index.…”

“…The existence of these correlations is predicted for Pu-based materials 26 and is reflected in PuCoGa 5 through its enhanced electronic specific heat coefficient, g < 95 mJ mol 21 K 22 (ref. 17). As with the copper oxides and heavy-fermion systems like CeCoIn 5 , the Cooper pairing in PuCoGa 5 is most probably mediated by antiferromagnetic fluctuations arising from proximity to an antiferromagnetic/paramagnetic border.…”

Ab InitioElectronic Structure Calculations of Pu-115 Compounds

“…Ab initio calculations predicted antiferromagnetic order on the Pu atoms to be the most favorable long-range order. 3,7,9) Other results obtained for the superconductors PuCoGa 5 and PuRhGa 5 indicated a striking similarity 6) to the unconventional 19) heavy-fermion superconductors CeCoIn 5 , CeRhIn 5 and CeIrIn 5 . The Ce-115 compounds have been intensively investigated in the recent years.…”

“…6, 10) The T c of superconducting Pu-115 compounds was found to scale linearly with the c/a ratio, 6) which was suggested to influence the amount of two-dimensionality. The c/a ratio varies in a non-monotonous way across the series: 1.587, 1.604, 1.600, for the Fe, Co, and Ni Pu-115 compounds, respectively.…”

“…[2][3][4][5][6][7][8][9][10][11][12][13][14] The discovery of superconductivity in PuCoGa 5 can be compared with the discovery of superconductivity in the copper oxides: prior to its discovery, not a single Pu-based material was known to be a superconductor, and in addition, within the group of actinide-based superconductors, there exists practically no material with a T c above 2 K. In actinide science this particular aspect of plutonium compounds has previously been related to the common understanding that magnetism and superconductivity mutually exclude each other as collectively ordered electronic ground states (see, e.g., Ref. 15,16) ).…”