Louis R. Testardi

Louis R. Testardi, a pioneer in the discovery of A15 superconductors, passed away on 2 March 2017 at his home in Colorado after a long battle with Alzheimer’s disease.

Louis was born in Philadelphia in 1930. He joined the Army right after high school, planning to attend college afterward. However, as soon as he was discharged from the Army, he was called back to serve in the Korean War. Due to his specialization in communications, he was sent to Tokyo for a year to maintain the communication bridge between the Pentagon and the field operations in Korea. On 11 April 1951 Louis was asked to set up the communication bridge but not to listen to the orders that would follow that night. He was later to learn from a public address given to the nation by President Harry Truman that the president had just fired General Douglas MacArthur that night, justifying his policy to the world in Korea with the phrase “it is right for us to be in Korea.”

At the end of his service, he enrolled at the University of California, Berkeley, and obtained his BS in physics in 1955. After that, wanting to visit the land of his parents, Louis enrolled in graduate courses at the University of Rome. It was here that he met Fulvia Pieraccini, an Italian graduate student who was to become the love of his life. Married six months later, he wrote directly to President Dwight Eisenhower to petition for her quick admission to the US, as she was a nuclear physicist and therefore an important asset for the country. The year was 1957, a time when the perception of a threatening Soviet advantage in missile technology was rapidly increasing among the American people. On 4 October of that year, the Soviets had launched the first ever artificial satellite to orbit Earth. Shortly thereafter, Eisenhower addressed the nation, via radio and television, with a “Special message on Science and National Security” that launched the US into the space program and led to the creation of NASA in 1958. Because of these developments, scientists quickly became in high demand, especially nuclear physicists like Fulvia. She was granted an entry visa in a matter of a few weeks and happily joined her newlywed husband in the US. After his return to the US, Louis completed his studies and was awarded a PhD by the University of Pennsylvania in 1963.

Following his graduation, Louis became a member of the technical staff at Bell Laboratories, and while there was for a year a visiting professor at Princeton University. In 1973 Louis heard of the groundbreaking work of John Gavaler, who at Westinghouse R&D succeeded in sputtering thin (1 μm) films of metastable Nb₃Ge onto a heated substrate to produce a superconductor with a superconducting transition temperature onset of 22.3 K and a transition width of 1.5 K, setting a new record for the highest value of T_c of any material. Louis and his coworkers quickly duplicated Gavaler’s method, confirmed his remarkable result, and, in the process, found an even higher value of T_c of 23.2 +/- 0.2 K and a transition width of ~ 1.2 K. This record T_c obtained in 1974 by Gavaler and Testardi would only be surpassed 12 years later in 1986 with the discovery of cuprate superconductors by J. George Bednorz and K. Alex Müller at the IBM Zürich laboratory.

In 1979, together with Leonard F. Mattheiss, Louis worked toward establishing to what extent the physical properties of certain materials that are strongly modified by electron scattering processes are dependent on the sample quality. To this end, they formulated a simple model to describe the profound degree by which strain and disorder affect the superconducting properties of A15-(β-tungsten)-structure materials and bcc transition metals and alloys. The underlying idea in this model is that the energy of an electron in a disordered material is poorly defined when compared to the energy of an electron in a perfect crystal, because of the higher level of scattering that occurs in the disordered material. This effect is introduced through an electron lifetime broadening term that, coupled with density functional theory calculations, results in the prediction of all physical parameters of interest such as the density of states N(E_F) at the Fermi level, the Fermi velocity v_F, the Drude plasma frequency Ω_p, and ultimately with one assumption, a relation between T_c for superconductivity and the residual resistivity ρ₀. This empirical rule would later become known as the Testardi correlation, also shown to be fulfilled over a wide range of T_c and resistance residual ratios values applicable to a wide range of phonon-mediated superconducting compounds including MgB₂. Throughout these years, Louis was interested in phonon softening that accompanies structural instabilities, and whether these modes might lead to enhanced T_cs.

Louis left Bell Laboratories to join NASA as the director of the Materials Processing in Space Program from 1980 to 1982. At NASA, he worked on materials processing in the reduced gravity environment of space. After that, he joined the National Bureau of Standards (NBS) in 1982 as chief of the Metallurgy Division. During this time, he was an advocate for the transfer of vast resources of government sponsored research to resolve technical challenges of industrial problems.

In 1985, Louis left NBS to become professor of physics and founding director of a newly created Materials Research and Technology (MARTECH) center at Florida State University in Tallahassee. There he worked primarily on electric-field penetration, electric polarizability and dielectric measurements on YBa₂Cu₃O_7-δ compounds, and electrical transport properties of Fe₃O₄/NiO super-lattices. In 1988, MARTECH, under Louis’ leadership, was awarded a large grant from DARPA to lead the state of Florida in superconductivity research.

In later years, Louis worked privately and authored many patents pertaining to medical devices and homeland security. Louis was an enthusiastic researcher with a contagious sense of curiosity that positively energized and affected everyone around him. Personally, I would never be where I am in my career if it were not for my uncle Louis. He was simply a source of inspiration, admiration, and goodness for all of us who knew him.

Louis is survived by Fulvia, his children, Stephen, Mark, Richard, and David, and grandchildren Claire, Jonathan, and Lily.