Rokas Veitas Earns McQuade Fellowship

Rokas Veitas is putting a new spin on condensed matter physics.

"I'm investigating magnetic dynamics in a long-range interacting spin system," said Veitas, a Ph.D. student in Carnegie Mellon University's Department of Physics. "It's about setting up a lattice of atoms in particular positions, generating a particular pattern in their spins using a laser, and then watching how easily this pattern falls apart or moves."

Long-range interacting spin systems are lattices of atoms in two dimensions. In the lattice, each atom spins in a certain direction, and each atom's spin influences the other atoms. This means that the atoms tend to spin in the same direction. In most magnetic systems, atoms only affect the spins of their neighbors. In long-range interacting spin systems, atoms can be affected by other atoms across large distances.

Veitas investigates how these spins can be affected by external magnetism, and he likens the systems to a magnetized compass. If the compass is left alone, it points north. If a magnet is applied, the compass points in the same direction as the magnet. However, if the magnet and the Earth's natural magnetic field are both exerting the same amount of magnetic force on the compass, it spins out of control with no clear direction of where to point.

Atoms in long-range systems respond in a similar way to applied magnetic fields, and Veitas is most interested in when the atoms are out of control, known as the critical point.

"If I poke at the system a little bit, or if I throw something at it, or if I heat it up, what happens?" Veitas said. "What you get is a spin wave or a magnon, and our question is how many of these are there, and how long do they stick around?"

By learning how these atoms interact, Veitas' research could have potential technological implications in the future.

"You can use this system to find out a lot about other systems which you might not be able to," Veitas said.

Veitas is part of the Chatterjee group run by Shubhayu Chatterjee, assistant professor of physics. Chatterjee said that Veitas' work is helping to answer questions about how atoms interact with each other.

"Rokas is leading an important project that asks basic questions about dynamics of long-range interacting physical systems," Chatterjee said. "Answering such questions in the context of his specific model holds the key to our understanding of how long-range interactions affect the spread of correlations."

For his work, Veitas earned the J. Michael McQuade Nanophysics and Energy Fellowship, which allows students to participate in the early stages of a new research direction before grant funding has been obtained.

"I'm really happy to be receiving the fellowship," Veitas said. "It's really great that it allows me extra time to do my research and focus on the thing that I love."