P H Y S IC S A N D A S T RO NOM Y
QUESTION
The theory correctly described how the
Can a quantum phase such as superconductivity, on the
evolution of superconductivity depends on critical
verge of its emergence, be measured and controlled in a
temperature, magnetic field magnitude and
lab experiment?
orientation, nanowire cross sectional area, and the
“To answer these fundamental questions, we fabricated extremely narrow and uniform nanowires at the U and conducted accurate transport
microscopic characteristics of the nanowire material. The study was published July 9, 2018 in Nature Physics. To test Del Maestro’s theory, Rogachev needed
measurements in the laboratory of my collaborator,
nearly one-dimensional nanowires, with diameters
Benjamin Sacépé, in Grenoble, France,” says Andrey
smaller than 20 nanometers.
Rogachev, an Associate Professor of Physics and Astronomy at the U.
“In theoretical physics, one-dimensional systems play a special role, since for them an exact theory can be developed,” says Rogachev. “Yet one-dimensional
WHO Rogachev and his colleagues discovered that superconducting nanowires made of molybdenum
Controlling the Quantum Realm ANDREY ROGACHEV
systems are notoriously difficult to deal with experimentally.” The molybdenum germanium nanowires are
germanium (MoGe) alloy undergo quantum phase
the crucial element of the study. In his postdoctoral
transitions from a superconducting state to a normal
days, Rogachev could only make such wires 100
metal state when placed in an increasing magnetic
nanometers long, which is too short to test the critical
field at ultra-low temperatures.
regime. Years later, at the University of Utah, he
The study is the first to uncover the
and his then-student Hyunjeong Kim – lead author
complex process by which the material loses its
of the study – improved upon an existing method
superconductivity; the magnetic field breaks apart
of electron beam lithography to develop a novel
pairs of electrons, called Cooper pairs, which then
technique capable of fabricating the nearly
interact with other Cooper pairs and experience a
one-dimensional nanowires.
damping force from unpaired electrons present in the system.
14
FUNDING
The findings are fully explained by the critical
Since Rogachev joined the U in 2006, his research
theory proposed by coauthor Adrian Del Maestro,
has been supported by a National Science Foundation
Associate Professor at the University of Vermont.
CAREER grant of $550,000 and by a regular NSF
