Fundamental Transport Mechanisms in Disordered Nanostructured Networks
CIC nanoGUNE Seminars
- Speaker
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Karolina Z. Milowska
CIC nanoGUNE - When
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2025/11/03
11:00 - Place
- CIC nanoGUNE Seminar room, Tolosa Hiribidea 76, Donostia-San Sebastian
- Host
- Daniel Hernangómez
- Add to calendar
-
iCal
Understanding magnetotransport in disordered quantum materials remains a major challenge in condensed matter physics. A variety of models — quantum interference, variable‑range hopping, weak or fluctuation‑induced tunnelling, and hybrid metallic‑insulating frameworks — are frequently used to interpret magnetotransport in disordered systems, yet no unified theory can reliably describe observations across all materials. Carbon nanotube (CNT) networks provide an ideal testbed for this problem: their electronic character can be tuned from metallic to semiconducting or semimetallic simply by changing chirality, while their hierarchical structure captures the complexity of real nanostructured conductors.
In this talk, I will discuss our recent progress in unifying experiment and theory to uncover the fundamental transport mechanisms in disordered nanostructured networks. Using ultrahigh-field magnetotransport experiments (1.5K-300K & up to 60 T) performed at the Los Alamos National Laboratory, we identified a crossover from metallic to semiconducting-like behavior in CNT fibers and films, MR sign reversals, non-monotonic temperature dependences, and low-T plateaus indicative of fluctuation-assisted transport [1].
To interpret these findings microscopically, we developed a new multiscale magnetotransport modelling paradigm that combines quantum-coherent tight-binding transport calculations (TB-NEGF), external magnetic field effects via Peierls substitution, and Molecular Dynamics (MD) simulations. This framework reproduces the experimental trends and reveals how inter-tube tunnelling, defect scattering, and quantum interference shape magnetoresistance across junctions, bundles, and complex looped geometries, guiding the design of advanced magnetoresistive composites.
Together, the combined experimental–theoretical approach demonstrates that even macroscopic CNT conductors are ultimately defined by quantum interference at the nanoscale. The insights gained establish design principles for tuning conductivity and magnetoresistance in nanocarbon networks and other disordered quantum materials.
[1] J. Bulmer, C. Kovacs, T. Bullard, C. Ebbing, T. Haugan, G. Pokharel, S. D. Wilson, F. F. Balakirev, O. A. Valenzuela, M. A. Susner, D. Turner, P. Fu, T. Kulka, J. A. Majewski, I. Lebedeva, K. Z. Milowska, A. Lekawa-Raus, M. Marganska “Adjudicating Conduction Mechanisms in High Performance Carbon Nanotube Fibers” arXiv:2507.20481