Two CERN theoretical physicists have taken a page out of Google’s playbook in an attempt to better measure the impact of scientists and their published research. In a recent study published on arXiv, Alessandro Strumia and Riccardo Torre propose new metrics that use principles of Google’s PageRank algorithm, which determines the order in which websites appear in search results.

Experiments that measure the lifetime of neutrons reveal a perplexing and unresolved discrepancy. While this lifetime has been measured to a precision within 1 percent using different techniques, apparent conflicts in the measurements offer the exciting possibility of learning about as-yet undiscovered physics.

Now, a team led by scientists in the Nuclear Science Division at the Department of Energy’s Lawrence Berkeley National Laboratory (Berkeley Lab) has enlisted powerful supercomputers to calculate a quantity known as the “nucleon axial coupling,” or g_A—which is central to our understanding of a neutron’s lifetime—with an unprecedented precision. Their method offers a clear path to further improvements that may help to resolve the experimental discrepancy.

Illinois Physics alumnus Chia Cheng “Jason” Chang is lead author on the paper. Chang received his bachelor’s degree in 2008 and his doctoral degree in 2015, both from the Department of Physics at the University of Illinois at Urbana-Chmpaign. Chang’s doctoral adviser at Illinois was Professor Aida El-Khadra. These results were achieved while Chang was a postdoctoral researcher in Berkeley Lab’s Nuclear Science Division. Chang currently holds an appointment as a research scientist at the Interdisciplinary Theoretical and Mathematical Sciences Program (iTHEMS) of the Institute of Physical and Chemical Research (RIKEN), Japan.

We analyze the interplay between a $d$-wave uniform superconducting and a pair-density-wave (PDW) order parameter in the neighborhood of a vortex. We develop a phenomenological nonlinear sigma model, solve the saddle-point equation for the order-parameter configuration, and compute the resulting local density of states in the vortex halo. The intertwining of the two superconducting orders leads to a charge density modulation with the same periodicity as the PDW, which is twice the period of the charge density wave that arises as a second harmonic of the PDW itself. We discuss key features of the charge density modulation that can be directly compared with recent results from scanning tunneling microscopy and speculate on the role PDW order may play in the global phase diagram of the hole-doped cuprates.

Now, a novel sample-growing technique developed at the U. of I. has overcome these obstacles. Developed by physics professor James Eckstein in collaboration with physics professor Tai-Chang Chiang, the new “flip-chip” TI/SC sample-growing technique allowed the scientists to produce layered thin-films of the well-studied TI bismuth selenide on top of the prototypical SC niobium—despite their incompatible crystalline lattice structures and the highly reactive nature of niobium.

These two materials taken together are ideal for probing fundamental aspects of the TI/SC physics, according to Chiang: “This is arguably the simplest example of a TI/SC in terms of the electronic and chemical structures. And the SC we used has the highest transition temperature among all elements in the periodic table, which makes the physics more accessible. This is really ideal; it provides a simpler, more accessible basis for exploring the basics of topological superconductivity,” Chiang comments.

Associate Head for Graduate Programs and Professor S. Lance Cooper has been awarded the 2018 Excellence in Graduate Student Mentoring Award of the Office of the Provost at the University of Illinois at Urbana-Champaign.

One of the Campus Awards for Excellence in Instruction conferred annually at the campus’s Celebration of Teaching Excellence, this accolade recognizes sustained excellence in graduate student mentoring; innovative approaches to graduate advising; major impact on graduate student scholarship and professional development; and other contributions in the form of courses and curricula, workshops, or similar initiatives. Cooper was presented with the award on April 12, 2018.

The University of Illinois has received a three-year, $1 million grant from the Alfred P. Sloan Foundation to continue funding for the Sloan University Center of Exemplary Mentoring at Illinois. The program, started in 2015, supports underrepresented minority doctoral students in science, technology, engineering and math fields and is one of nine UCEMs throughout the country.

The UCEM emphasizes mentoring, professional development and social activities to build a community of scholars. The center hosts an extensive orientation program for new students, workshops and seminars in addition to financial support in the form of scholarships. The center also works with departments to set up a mentoring team for each scholar and monitors academic and research progress.