Department of Physics & Texas Center for Superconductivity

Physical science research at the University of Houston encompasses a wide range of topics including collaborations with the Large Hadron Collider in Geneva and Relativistic Heavy Ion Collider at Brookhaven

The experiments simulate the universe’s first few microseconds, by colliding heavy ions to create quark-gluon plasmas. Here we focus on some research activities, by the Miller group and collaborators, in quantum materials and biological physics.

Quantum materials are critical to quantum information systems, which will only attain their full potential if they can operate without large, expensive dilution refrigerators. We study collective quantum systems, potentially more thermally robust than single quanta [1-3]. The charge density wave (CDW) is a condensate of electrons that forms in certain layered materials, sometimes well above room temperature. Its quantum nature is revealed by several lines of evidence. Experiments often show lack of CDW displacement when biased just below the threshold electric field for nonlinear transport, indicating the CDW never reaches the critical point for classical depinning.

Quantum behavior is further revealed by oscillations of period h/2e in CDW conductance vs. magnetic flux in CDW rings above 77 K. We have also found that, for temperatures ranging from 9 to 474 K, CDW current-voltage plots of trichalcogenide materials agree with time-correlated soliton tunneling model simulations [1]. In our model we treat the Schrödinger equation as an emergent equation that describes fluidic Josephson-like coupling of paired electrons between evolving topological states. We find that an extension of this ‘classically robust’ quantum picture explains the h/2e magnetoconductance oscillations in CDW rings. Potential applications include thermally robust quantum information processing and quantum machine learning.

We aim to further test aspects of our time-correlated soliton tunneling picture in some upcoming experiments.  We plan to carry out spatially resolved X-ray diffraction (XRD) of satellite CDW peaks vs. bias current, in collaboration with the National Synchrotron Light Source II at Brookhaven National Laboratory. By measuring changes in CDW XRD satellite peak, one can determine the extent to which the CDW deforms and displaces between the contacts.  This will potentially corroborate other experiments showing lack of CDW displacement below threshold and provide further evidence for quantum rather than classical transport.

In the area of biological physics, our previous work includes dielectric spectroscopy as a label-free method to probe changes in membrane potential of cells or mitochondria in suspension. Together with collaborators in physics, biology, and biochemistry, we have also studied physical aspects of mutations – how the quantum physics of DNA affects site-specific mutation rates, and how amino acid replacements affect certain biological motors.  Using ‘computational DNA hole spectroscopy,’ we have found that DNA mutates more readily at sites where electron holes tend to localize [4,5]. This has implications for molecular evolution and for diseases affected by mutations.

Finally, we have carried out molecular dynamics studies of normal and mutation-impaired water channels in the rotary motor ATP synthase, which produces adenosine triphosphate (ATP) in the mitochondrial electron transport chain. Through molecular dynamics we have found that certain mitochondrial diseases, such as Leigh syndrome, are caused by a ‘short circuit’ between proton-conducting water channels, which impairs ATP production. This sometimes afflicts children with this devastating hereditary mitochondrial disorder.

1. Miller, J. H., Jr., Suárez-Villagrán, M. Y., & Sanderson, J. O. Quantum Transport of Charge Density Wave Electrons in Layered Materials. Materials Today Physics 41, 101326  https://doi.org/10.1016/j.mtphys.2024.101326 (2024).
2. Miller, J. H., Jr. & Suárez-Villagrán, M. Y. Quantum fluidic charge density wave transport. Applied Physics Letters 118, 184002, doi:10.1063/5.0048834 (2021).
3. Miller, J. H., Villagrán, M. Y. S., Sanderson, J. O. & Wosik, J. Hybrid Quantum Systems for Higher Temperature Quantum Information Processing. IEEE Transactions on Applied Superconductivity 33, 1-4, doi:10.1109/TASC.2023.3241131 (2023).
4. Suárez Villagrán, M. Y. & Miller, J. H. Computational DNA hole spectroscopy: A new tool to predict mutation hotspots, critical base pairs, and disease ‘driver’ mutations. Scientific Reports 5, 13571-13571 https://doi.org/10.1038/srep13571 (2015).
5. Suárez-Villagrán, Azevedo, R. B. R. & Miller, J. H., Jr. Influence of Electron–Holes on DNA Sequence-Specific Mutation Rates. Genome Biology and Evolution 10 (4), 1039-1047 https://academic.oup.com/gbe/article/10/4/1039/4951197 (2018).