using the nanoscale to have large-scale impact.

new physics, built atom by atom.

We design states of matter one atomic layer at a time. Our group uses atomic-scale materials synthesis to create and control states that are difficult, or sometimes impossible, to access in bulk materials. We grow epitaxial thin films and heterostructures with atomic precision, using dimensional confinement, interfaces, strain, electrostatic boundary conditions, and crystal symmetry to modify the interactions that govern electronic, magnetic, and structural order. In this way, synthesis becomes a tool for engineering the underlying physics of a material.

We are particularly interested in quantum materials in which spin, charge, orbital, lattice, and polarization degrees of freedom are strongly coupled. By deliberately reorganizing these interactions, we seek to stabilize new magnetic phases, topological textures, and electronic responses, and then develop ways to control them using electric fields, currents, strain, and other external stimuli. Our work spans multiferroics and altermagnets, polar metals, superconductors, spin-orbit and orbital phenomena, and other correlated materials.

To connect atomic-scale design with measurable functionality, we combine thin-film synthesis with electrical transport, magnetic and optical measurements, scanning-probe microscopy, synchrotron-based characterization, and device fabrication. A central goal of the group is to understand how new physics emerges when materials are pushed beyond their conventional bulk structures, and how these states can ultimately enable new approaches to information processing, sensing, and energy technologies.

Bonus – We are always interested in exploring new applications of our materials, devices, and their functionalities in creative and imaginative ways, including potential application is biomedical engineering, batteries, mechanics, and more.

Key words: quantum materials, spintronics and magnetism, ferroelectricity, multiferroics, spin-orbit coupling, interface engineering, oxide thin films, epitaxial thin films, emergent phenomena, atomically-precise growth, device design and lithography, magneto-optics, magnetotransport

Latest Discoveries and Innovations

Ultrathin multiferroics and emergent altermagnetism

Our team has discovered that multiferroic order in BiFeO₃ can persist down to only four unit cells, or about 1.6 nm, without the conventional “dead layer” expected at this scale. This is important because removing the dead layer gives access to an ultrathin regime where confinement can reorganize the magnetic ground state without first destroying the ferroic order. At four unit cells, the bulk-like cycloid is suppressed and a new collinear magnetic phase emerges with signatures consistent with altermagnetism.

The broader idea is that the ultrathin limit does not simply shrink the bulk material. It can liberate phases that are otherwise inaccessible. By controlling thickness together with electrostatic boundary conditions, strain, and atomic-scale structure, new magnetic states and topological textures can be stabilized that do not exist in bulk BiFeO₃.

G Fratian, M Ramesh, X Li, … , L. Caretta, Topological textures and emergent altermagnetic signatures in ultrathin BiFeO3. arXiv:2601.09970

Ultrafast, low power, voltage-driven Klein bottle topology

We discovered a new way to move magnetic and multiferroic topological textures using electric fields rather than electrical current. In BiFeO₃, lateral electric fields can translate coupled ferroelectric and antiferromagnetic defects over long distances, creating a voltage-driven racetrack for topological information.

Because the motion does not require charge current to flow through the material, the approach can operate with extremely low energy dissipation while retaining very high speeds. The textures themselves also reveal unusual topology, including non-Abelian defect structures associated with the cycloidal magnetic order. This work points toward a new class of magnetoelectric devices in which information is written and transported directly through electric-field control of magnetic structure.

A Ghosal, A Qualls, Y Nahas, … , L. Caretta, Low-energy domain wall racetracks with multiferroic topologies. arXiv:2507.12633

Reaching the relativistic magnonic speed limit

We report the first experimental demonstration of relativistic motion of a magnetic soliton, made possible by harnessing new spin physics and materials that allow for ultralow dissipation dynamics resulting in the fastest current-driven domain walls ever reported. The entire framework of magnetic domain wall dynamics is premised on the idea that the “stiffer” a domain wall is, the faster it can move. Here, we show that this behavior finally breaks down in a most remarkable way at high speeds, for exactly the same reason, mathematically, that no particle can exceed the speed of light.

L. Caretta, S.-H. OH, T. Fakhrul, et al. “Relativistic kinematics of a magnetic soliton,” Science, vol. 18, p. 1438-1442 (2020)