About

Professor Alex Frañó is the Principal Investigator of the Frano X Lab, also known as The X-ray Laboratory for Research on Quantum Materials, based at the University of California, San Diego. His research group focuses on studying the fascinating properties of materials with strongly correlated electrons. They investigate long-range periodicities in the spin, charge, and orbital quantum states observed in transition-metal-oxide films, superlattices, heterostructures, and single crystals. To explore these spatially periodic behaviors, the lab operates in Fourier space by performing modern x-ray scattering experiments at synchrotrons around the world. The research process involves determining material components of heterostructures, growing samples using pulsed laser deposition (PLD), characterizing samples at UCSD using x-rays and other in-house facilities, applying for beam time at synchrotrons, and using synchrotron x-rays to characterize materials and discover new periodicities. The data analysis is performed using Python, Matlab, and Mathematica, followed by writing and sharing discoveries. Professor Frañó's lab has contributed to advancing the understanding of quantum materials at the nanoscale, including studies on stimuli-driven switching using state-of-the-art x-ray experimental tools and visualization of structural filaments in vanadate neuromorphic devices. The lab's work has been featured in notable publications and at major synchrotron facilities such as the Advanced Photon Source at Argonne National Lab.

Research topics

• Computer Science
• Quantum mechanics
• Physics
• Artificial Intelligence
• Condensed matter physics
• Materials science
• Engineering
• Biology
• Computational biology
• Nanotechnology
• Optoelectronics
• Geometry
• Electrical engineering
• Engineering physics
• Chemistry

Selected publications

• Superconductivity suppression and bilayer decoupling in Pr-substituted YBa ₂ Cu ₃ O _{7− <i>δ</i>}

  Proceedings of the National Academy of Sciences · 2026-05-13

  articleOpen access

  The mechanism behind superconductivity suppression induced by Pr substitutions in YBa 2 Cu 3 O 7− δ (YBCO) has been a mystery since its discovery: in spite of being isovalent to Y 3+ with a small magnetic moment, it is the only rare-earth element that has a dramatic impact on YBCO’s superconducting properties. Using angle-resolved photoemission spectroscopy (ARPES) and DFT+ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline" overflow="scroll"> <mml:mi>U</mml:mi> </mml:math> calculations, we uncover how Pr substitution modifies the low-energy electronic structure of YBCO. Contrary to the prevailing Fehrenbacher–Rice (FR) and Liechtenstein–Mazin (LM) models, the low-energy electronic structure contains no signature of any f -electron hybridization or additional f -state Fermi surface sheets. Yet, strong electron doping is observed primarily on the antibonding Fermi surface. Meanwhile, we reveal major electronic structure modifications to Cu-derived states with increasing Pr substitution: a pronounced CuO 2 bilayer decoupling and enhanced hopping along the CuO chain, implying indirect electron-release pathways beyond simple 4 f state ionization. Our results challenge the long-standing FR/LM mechanism, and establish Pr substituted YBCO as a potential platform for exploring correlation-driven phenomena in coupled 1D–2D systems.

  PublisherDOI

• Role of Polymer–Protein Interactions in the Dynamics of Polymer-Integrated Protein Crystals

  Journal of the American Chemical Society · 2026-04-24

  article

  The incorporation of synthetic polymers into biomolecular materials provides a powerful strategy to enhance their properties. We recently showed that the interstitial spaces of highly solvated mesoporous ferritin crystals could be infiltrated with acrylate (Ac) and acrylamide (Am) monomers, which are subsequently polymerized in crystallo to yield a new class of hybrid materials termed Polymer-Integrated Protein Crystals (PIX). Our earlier studies had shown that ferritin-PIX displayed remarkable properties such as reversible expansion and contraction without losing crystalline order, efficient self-healing, and the ability to encapsulate and release large biomolecular cargo. However, the structure of the polyacrylate-co-acrylamide (p(Ac–Am)) polymer matrix, its distribution within the protein lattice, and the molecular nature of the protein–polymer interactions that ultimately engender the emergent properties of ferritin-PIX have remained unknown. Here, we combine small-angle neutron and X-ray scattering and analytical measurements with extensive all-atom and coarse-grained molecular dynamics simulations to examine the structure and dynamics of the polymer network within the crystalline framework of ferritin-PIX. Our results reveal an extensive and multivariate set of noncovalent interactions between the ferritin surfaces and p(Ac–Am) chains that sustain the structural coherence of the crystalline lattice while accommodating large-scale motions. Guided by these insights, we have demonstrated that changes in the chemical compositions of ferritin and the polymer matrix can be used to predictably control the structural dynamics of ferritin-PIX. Our increased molecular-level understanding and engineering of the polymer–protein interface in ferritin-PIX provide an important step toward the generalization of the PIX concept to other protein crystals and polymer compositions.

  PublisherDOI

• High-Resolution Full-Field Structural Microscopy of the Voltage-Induced Filament Formation in VO₂-Based Neuromorphic Devices

  ACS Nano · 2025-04-14 · 8 citations

  articleOpen accessSenior author

  , mediated by sites within the device gap that tend to switch at significantly lower voltages after electrical cycling, a tendency that persists through a brief thermal reset. High spatial resolution, large field-of-view, structure selectivity, and fast signal acquisition of DFXM provided insight into structural features of the filamentary channel and surrounding regions during voltage cycling.

  PublisherDOI

• Temperature Dependent Spin Dynamics in La_0.67Sr_0.33MnO₃/Pt Bilayers

  Advanced Materials Interfaces · 2025-04-04 · 1 citations

  articleOpen access

  Abstract Complex ferromagnetic oxides such as La 0.67 Sr 0.33 MnO 3 (LSMO) offer pathways for creating energy‐efficient spintronic devices with new functionalities. LSMO exhibits high‐temperature ferromagnetism, half metallicity, sharp resonance linewidth, low damping, and a large anisotropic magnetoresistance response. Combined with Pt, a proven material with high spin‐charge conversion efficiency, LSMO can be used to create robust nano‐oscillators for neuromorphic computing. Ferromagnetic resonance (FMR) and device‐level spin‐pumping FMR measurements are performed to investigate the magnetization dynamics and spin transport in NdGaO 3 (110)/LSMO(15 nm)/Pt(0 and 5 nm) thin films ranging from 300 K to 90 K and compare the device performance with Py(7 nm)/Pt(5 nm) sample. The spin current pumped into Pt is quantified to determine the temperature‐dependent influence of interfacial interactions. The generated spin current in the micro‐device is maximum at 170 K for the optimally grown LSMO/Pt films. Additionally, this bilayer system exhibits low magnetic Gilbert damping (0.002), small linewidth (12 Oe), and a large spin Hall angle (≈3.2%) at 170 K. Ex situ deposited LSMO/Pt bilayers demonstrate excellent dynamic response, exhibiting fourfold enhancement in signal output, eightfold reduction in damping, and a threefold reduction in linewidth as compared to the Pt/Py system. Such robust device‐level performance can pave way for energy‐efficient spintronic‐based devices.

  PublisherOA PDFDOI

• Superconductivity suppression and bilayer decoupling in Pr substituted YBa$_2$Cu$_3$O$_{7-δ}$

  Desy publication database (The Deutsches Elektronen-Synchrotron) · 2025-10-16

  articleOpen access

  The mechanism behind superconductivity suppression induced by Pr substitutions in YBa$_2$Cu$_3$O$_{7-δ}$ (YBCO) has been a mystery since its discovery: in spite of being isovalent to Y$^{3+}$ with a small magnetic moment, it is the only rare-earth element that has a dramatic impact on YBCO's superconducting properties. Using angle-resolved photoemission spectroscopy (ARPES) and DFT+$U$ calculations, we uncover how Pr substitution modifies the low-energy electronic structure of YBCO. Contrary to the prevailing Fehrenbacher-Rice (FR) and Liechtenstein-Mazin (LM) models, the low energy electronic structure contains no signature of any $f$-electron hybridization or new states. Yet, strong electron doping is observed primarily on the antibonding Fermi surface. Meanwhile, we reveal major electronic structure modifications to Cu-derived states with increasing Pr substitution: a pronounced CuO$_2$ bilayer decoupling and an enhanced CuO chain hopping, implying indirect electron-release pathways beyond simple 4$f$ state ionization. Our results challenge the long-standing FR/LM mechanism and establish Pr substituted YBCO as a potential platform for exploring correlation-driven phenomena in coupled 1D-2D systems.

  PublisherDOI

• Spectroscopic Determination of Site-Selective Ligand Binding on Single Anisotropic Nanocrystals

  Research Square · 2025-10-14

  preprintOpen accessSenior author
  PublisherOA PDFDOI

• Demonstration of a dual-beam zone plate for phase-contrast coherent soft x-ray imaging

  2025-09-18

  article

  Coherent x-ray imaging faces fundamental speed limitations due to computational reconstruction requirements of current phase retrieval methods. We demonstrate dual-beam zone plates that enable direct phase-contrast measurements by structuring coherent x-rays into two focused 110nm spots separated by 11μm, bypassing iterative algorithms entirely. Experimental validation at the COSMIC beamline confirms precise dual-beam formation with clear interference patterns analogous to Young’s double-slit experiment. Comparative measurements reveal enhanced sensitivity: phase detection achieves 45° phase shifts at sample boundaries where intensity contrast shows poor signal clarity due to noise. Spectroscopic demonstrations across the oxygen K-edge show energy-selective capabilities, with phase features providing improved signal-to-noise ratio compared to conventional absorption measurements. The high photon efficiency of this direct measurement approach enables fast imaging capabilities, making the technique well-suited for studying dynamic processes in quantum materials with next-generation synchrotron sources.

  PublisherDOI

• Spectroscopic Determination of Site-Selective Ligand Binding on Single Anisotropic Nanocrystals

  ArXiv.org · 2025-10-14

  preprintOpen accessSenior author

  Organic surface ligands are integral components of nanocrystals and nanoparticles that have a strong influence on their physicochemical properties, their interaction with the environment, and their ability to self-assemble and order into higher-order structures. These hybrid nanomaterials are tunable with applications in catalysis, directed self-assembly, next-generation optoelectronics, and chemical and quantum sensing. Critically, future advances depend on our ability to rationally engineer their surface chemistry. However, fundamental knowledge of ligand-nanoparticle behavior is limited by uncertainty in where and how these ligands bind to surfaces. For nanoparticles, in particular, few characterization techniques offer both the high spatial resolution and the precise chemical mapping needed to identify specific ligand binding sites. In this study, we utilized synchrotron infrared nanospectroscopy (SINS), atomic force microscopy (AFM), and scanning tunneling microscopy (STM) together with first-principles computer simulations to validate the site-selective adsorption of organic ligands on a shaped nanocrystal surface. Specifically, we demonstrate that the sterically encumbered isocyanide ligands (CNAr^{Mes2}) preferentially bind to the high curvature features of Ag nanocubes (NCs), where low-coordinate Ag atoms are present. In contrast, isocyanide ligands that do not exhibit these steric properties show no surface selectivity. SINS serves as an effective tool to validate these surface binding interactions at the near-single molecule level. These results indicate that steric effects can be successfully harnessed to design bespoke organic ligands for fine-tuning nanocrystal surface chemistry and the properties of the nanocrystal ligand shell.

  PublisherOA PDFDOI

• Temperature dependent spin dynamics in La$_{0.67}$Sr$_{0.33}$MnO$_3$/Pt bilayers

  arXiv (Cornell University) · 2024-11-23

  preprintOpen access

  Complex ferromagnetic oxides such as La$_{0.67}$Sr$_{0.33}$MnO$_3$ (LSMO) offer pathways for creating energy efficient spintronic devices with new functionalities. LSMO exhibits high-temperature ferromagnetism, half metallicity, sharp resonance linewidth, low damping and a large anisotropic magnetoresistance response. Combined with Pt, a proven material with high spin-charge conversion efficiency, LSMO can be used to create robust nano-oscillators for neuromorphic computing. Ferromagnetic resonance (FMR) and device level spin-pumping FMR measurements are performed to investigate the magnetization dynamics and spin transport in NdGaO3(110)/LSMO(15 nm)/Pt(0 and 5 nm) thin films ranging from 300K to 90K and compare the device performance with Py(7 nm)/Pt(5 nm) sample. The spin current pumped into Pt is quantified to determine the temperature dependent influence of interfacial interactions. The generated spin current in the micro-device is maximum at 170K for the optimally grown LSMO/Pt films. Additionally, this bilayer system exhibits low magnetic Gilbert damping (0.002), small linewidth (12 Oe) and a large spin Hall angle ($\approx$ 3.2%) at 170K. By fine-tuning the LSMO/Pt interface quality and integrating it into the device structure, the system exhibits a fourfold enhancement in signal output for LSMO/Pt devices compared to the Pt/Py system. Such robust device level performance can pave way for energy-efficient spintronic based devices.

  PublisherOA PDFDOI

• Direct detection system for full-field nanoscale X-ray diffraction-contrast imaging

  Optics Express · 2024-05-27 · 4 citations

  articleOpen access

  Recent developments in X-ray science provide methods to probe deeply embedded mesoscale grain structures and spatially resolve them using dark field X-ray microscopy (DFXM). Extending this technique to investigate weak diffraction signals such as magnetic systems, quantum materials and thin films prove challenging due to available detection methods and incident X-ray flux at the sample. We present a direct detection method developed in conjunction with KAImaging which focuses on DFXM studies in the hard X-ray range of 10s of keV and above capable of approaching nanoscale resolution. Additionally, we compare this direct detection scheme with routinely used scintillator-based optical detection and achieve an order of magnitude improvement in exposure times allowing for imaging of weakly diffracting ordered systems.

  PublisherDOI

Frequent coauthors

• B. Keimer

  Max Planck Institute for Solid State Research

  58 shared

• E. Schierle

  Helmholtz-Zentrum Berlin für Materialien und Energie

  40 shared

• R. J. Birgeneau

  39 shared

• E. Weschke

  Helmholtz-Zentrum Berlin für Materialien und Energie

  36 shared

• Ronny Sutarto

  32 shared

• S. Blanco-Canosa

  Ikerbasque

  32 shared

• M. Minola

  Max Planck Institute for Solid State Research

  30 shared

• Martin Bluschke

  30 shared

Labs

• Frano X LabPI

Education

• B.S., Physics

  National University of Honduras

• M.S., Physics

  University of Stuttgart

• Ph.D., Physics

  Max Planck Institute for Solid State Research

Awards & honors

• Ernst-Eckhard-Koch Prize
• Springer Outstanding PhD Research Prize
• UC Presidential Postdoctoral Fellowship
• Sloan Research Award 2020
• Cottrell Scholar Award 2021