Radio Interview: Professor Charles Stafford

Yemille Medina

"Wake up Tucson it's your town, get up and get involved" the introduction to Wake Up Tucson 1030 KVOI, with Chris DeSimone, this is a local radio station bringing to light different topics to our community. Recently, Professor Stafford was invited to participate on this morning show, discussing various topics from his life history to his recent research. Listen to the podcast (credit: Wake Up Tucson 1030 KVOI)

We would like to congratulate Professor Stafford on receiving this opportunity to inform the community about research at the University of Arizona Physics Department. A summary of his specific research has also been included. Other links to Professor Charles Stafford and Ph.D. student Abhay Shastry research about basic concepts such as "hot" or "cold" apply to any system, even those far from equilibrium. Challenging established wisdom, the findings could possibly inform the design of future microelectronic devices and help bring some order around fundamental concepts in thermodynamics are attached below.

Link to UANews release:
https://uanews.arizona.edu/story/hidden-inferno-inside-your-laser-pointer

Link to Wildcat story:
http://www.wildcat.arizona.edu/article/2017/01/researchers-at-ua-improve...

Physical Review B:
http://journals.aps.org/prb/abstract/10.1103/PhysRevB.94.155433

Some like it hot: temperature and voltage in highly-excited quantum
systems
by Abhay Shastry and Charles A. Stafford
published in Physical Review B 94, 155433 (2016)
http://journals.aps.org/prb/abstract/10.1103/PhysRevB.94.155433
A "hot wire" could mean high voltage or high temperature, but is there some deeper connection
between these two concepts? Temperature and voltage are two basic variables developed in the
nineteenth century in the fields of thermodynamics and electrodynamics. So it may come as a shock
that such basic notions have until now lacked a mathematically rigorous definition except for the case
of equilibrium, an idealized case that does not actually occur in nature, except perhaps for the
hypothesized heat death of the universe eons in the future. In this article, we develop a rigorous theory
of local thermoelectric measurements in systems far from equilibrium and show that the notion of
temperature in such a system is ambiguous without specifying the voltage, and vice versa. Our
findings have important implications for scanning probe measurements of voltage (scanning
potentiometry) and temperature (scanning thermometry), implying that significant errors are
unavoidable if the two quantities are not measured simultaneously. Our analysis also provides a proof
of the positivity of the Onsager matrix of linear response theory, a statement of the second law of
thermodynamics that has lacked an independent proof for 85 years.