About

Sohrab Ismail-Beigi is the Strathcona Professor of Applied Physics & Materials Science at Yale Engineering, with additional appointments in Mechanical Engineering and Physics. His research group employs first principles computational methods to investigate fundamental questions in condensed materials theory and materials physics. His work encompasses a broad range of topics including semiconductor-oxide interfaces, growth strategies and structures, electronic, chemical, and mechanical properties of nanomaterials such as nanotubes, nanowires, 2D systems, and clusters, as well as the development of improved exchange and correlation models for complex oxides. His research also explores optical properties of nanostructures, photo-induced structural changes, and the chemistry and catalysis at transition metal oxide surfaces and interfaces. Dr. Ismail-Beigi has contributed to understanding and engineering interfaces for technological applications, and his work has been published in numerous scientific journals. He holds a Ph.D. from the Massachusetts Institute of Technology and is actively involved in advancing the field of materials physics through his research and academic leadership at Yale.

Selected publications

• Graduate Training in Quantum Information Science and Engineering: Lessons, Challenges, and a Roadmap from the NSF Research Traineeship Programs

  ArXiv.org · 2026-05-08

  articleOpen access

  Since 2019, eighteen NSF Research Traineeship (NRT) awards in quantum information science and engineering (QISE) and adjacent fields have been funded, constituting the largest NSF-coordinated investment in graduate QISE training in the United States. Synthesizing lessons from our programs, we work through the central tensions that every QISE graduate program must negotiate: between depth in a home discipline and breadth across the field, between structured instruction and open-ended experiential and hands-on learning, and between training individual specialists and cultivating teams that collectively cover all areas of QISE. We describe the structural and pedagogical innovations the NRT programs have developed in response, assess what is working and what remains unresolved, and sketch 12 open problems the community will need to address as QISE graduate education scales beyond the well-resourced research universities where it has up till now been mainly concentrated. Eight concrete recommendations follow: (1) adopt the startup model of team-based training as an organizing philosophy; (2) invest immediately in sensing and communication curriculum development; (3) build student agency into program governance, not just activities; (4) establish structural mechanisms for industrial engagement rather than depending on goodwill; (5) design for sustainability from year one; (6) develop graduate-level textbooks spanning all three QISE pillars: computing, sensing, and communications; (7) establish shared outcome assessment instruments across programs; and (8) develop structured mechanisms for faculty professional development in QISE.

  PublisherOA PDF

• Re-entrant unconventional superconductivity induced by rare-earth substitution in Nd1-xEuxNiO2 thin films

  Nature Communications · 2026-03-05

  articleOpen access

  High temperature superconductivity is typically associated with strong coupling and a large superconducting gap, yet these characteristics have not been demonstrated in the nickelates. Here, we provide experimental evidence that Eu substitution in the spacer layer of Nd_1-xEu_xNiO₂ (NENO) thin films enhances the superconducting gap, driving the system toward a strong-coupling regime. This is accompanied by a magnetic-exchange-driven magnetic-field-enhanced superconductivity. We investigate the upper critical magnetic field, H_c2, and the superconducting gap of superconducting NENO thin films with x = 0.2 to 0.35. Magnetoresistance measurements reveal magnetic-field-enhanced superconductivity in NENO films. We interpret this phenomenon as a result of an interaction between magnetic Eu ions and superconducting states in the Ni d_x2-y2 orbital. The upper critical magnetic field strongly violates the weak-coupling Pauli limit. Infrared spectroscopy confirms a large gap-to-T_c ratio <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mn>2</mml:mn><mml:mi>Δ</mml:mi><mml:mo>/</mml:mo><mml:msub><mml:mrow><mml:mi>k</mml:mi></mml:mrow><mml:mrow><mml:mi>B</mml:mi></mml:mrow></mml:msub><mml:msub><mml:mrow><mml:mi>T</mml:mi></mml:mrow><mml:mrow><mml:mi>c</mml:mi></mml:mrow></mml:msub><mml:mo>≃</mml:mo><mml:mn>5</mml:mn><mml:mo>-</mml:mo><mml:mn>6</mml:mn></mml:math>, indicating a stronger coupling pairing mechanism in NENO relative to the Sr-doped NdNiO₂. The substitution of Eu in the rare-earth layer causes pronounced modifications of the superconducting gap and magnetic interactions in Nd-based nickelates, opening new pathways to engineer high-T_c superconductivity in infinite-layer nickelates.

  PublisherDOI

• Graduate Training in Quantum Information Science and Engineering: Lessons, Challenges, and a Roadmap from the NSF Research Traineeship Programs

  arXiv (Cornell University) · 2026-05-08

  preprintOpen access

  Since 2019, eighteen NSF Research Traineeship (NRT) awards in quantum information science and engineering (QISE) and adjacent fields have been funded, constituting the largest NSF-coordinated investment in graduate QISE training in the United States. Synthesizing lessons from our programs, we work through the central tensions that every QISE graduate program must negotiate: between depth in a home discipline and breadth across the field, between structured instruction and open-ended experiential and hands-on learning, and between training individual specialists and cultivating teams that collectively cover all areas of QISE. We describe the structural and pedagogical innovations the NRT programs have developed in response, assess what is working and what remains unresolved, and sketch 12 open problems the community will need to address as QISE graduate education scales beyond the well-resourced research universities where it has up till now been mainly concentrated. Eight concrete recommendations follow: (1) adopt the startup model of team-based training as an organizing philosophy; (2) invest immediately in sensing and communication curriculum development; (3) build student agency into program governance, not just activities; (4) establish structural mechanisms for industrial engagement rather than depending on goodwill; (5) design for sustainability from year one; (6) develop graduate-level textbooks spanning all three QISE pillars: computing, sensing, and communications; (7) establish shared outcome assessment instruments across programs; and (8) develop structured mechanisms for faculty professional development in QISE.

  PublisherDOI

• Coulomb interaction written in terms of U, J, etc. and DFT+U

  Figshare · 2026-04-16

  otherOpen access1st authorCorresponding

  The idea of these notes is to look at the origin of localized Hubbard-like models for electron correlation effects and see what one can do exactly (very little) and then more approximately within a mean-field approximation such as DFT, Hartree-Fock or the like. One of the other aims is to present background information as well as some derivations and explanations of the various forms and outcomes that are used in DFT+U calculations. These are meant to be graduate-level pedagogical readings that we have found useful in my research group.

  PublisherDOI

• Coulomb interaction written in terms of U, J, etc. and DFT+U

  Figshare · 2026-04-16

  otherOpen access1st authorCorresponding

  The idea of these notes is to look at the origin of localized Hubbard-like models for electron correlation effects and see what one can do exactly (very little) and then more approximately within a mean-field approximation such as DFT, Hartree-Fock or the like. One of the other aims is to present background information as well as some derivations and explanations of the various forms and outcomes that are used in DFT+U calculations. These are meant to be graduate-level pedagogical readings that we have found useful in my research group.

  PublisherDOI

• Re-entrant unconventional superconductivity induced by rare-earth substitution in Nd1-xEuxNiO2 thin films

  Nature Communications · 2026-03-05

  articleOpen access

  High temperature superconductivity is typically associated with strong coupling and a large superconducting gap, yet these characteristics have not been demonstrated in the nickelates. Here, we provide experimental evidence that Eu substitution in the spacer layer of Nd1-xEuxNiO2 (NENO) thin films enhances the superconducting gap, driving the system toward a strong-coupling regime. This is accompanied by a magnetic-exchange-driven magnetic-field-enhanced superconductivity. We investigate the upper critical magnetic field, Hc2, and the superconducting gap of superconducting NENO thin films with x = 0.2 to 0.35. Magnetoresistance measurements reveal magnetic-field-enhanced superconductivity in NENO films. We interpret this phenomenon as a result of an interaction between magnetic Eu ions and superconducting states in the Ni dx2-y2 orbital. The upper critical magnetic field strongly violates the weak-coupling Pauli limit. Infrared spectroscopy confirms a large gap-to-Tc ratio $$2\Delta /{k}_{B}{T}_{{\rm{c}}}\simeq 5-6$$, indicating a stronger coupling pairing mechanism in NENO relative to the Sr-doped NdNiO2. The substitution of Eu in the rare-earth layer causes pronounced modifications of the superconducting gap and magnetic interactions in Nd-based nickelates, opening new pathways to engineer high-Tc superconductivity in infinite-layer nickelates. The authors provide experimental evidence that Eu substitution in the spacer layer of Nd1-xEuxNiO2 thin films enhances the superconducting gap, driving the system toward a strong-coupling regime. The Eu substitution also introduces exchange coupling between Eu 4f magnetic moments and Ni 3dx²−y² electrons, leading to magnetic-field-enhanced “re-entrant” superconductivity.

  PublisherDOI

• 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

• Layer-controlled orbital-selective Mott transition in monolayer nickelate

  Physical Review Research · 2025-09-23

  articleOpen access

  Dimensionality and electronic correlations are crucial elements of many quantum material properties. An example is the change of the electronic structure accompanied by the loss of quasiparticles when a metal is reduced from three dimensions to a lower dimension, where the Coulomb interaction between carriers becomes poorly screened. Here, using angle-resolved photoemission spectroscopy, we report an orbital-selective decoherence of spectral density in the perovskite nickelate <a:math xmlns:a="http://www.w3.org/1998/Math/MathML"> <a:mrow> <a:mi>LaNi</a:mi> <a:msub> <a:mi mathvariant="normal">O</a:mi> <a:mn>3</a:mn> </a:msub> </a:mrow> </a:math> toward the monolayer limit. The spectral weight of the <c:math xmlns:c="http://www.w3.org/1998/Math/MathML"> <c:msub> <c:mi>d</c:mi> <c:mrow> <c:mi>z</c:mi> <c:mn>2</c:mn> </c:mrow> </c:msub> </c:math> band vanishes much faster than that of the <d:math xmlns:d="http://www.w3.org/1998/Math/MathML"> <d:msub> <d:mi>d</d:mi> <d:mrow> <d:mi>x</d:mi> <d:mn>2</d:mn> <d:mo>−</d:mo> <d:mi>y</d:mi> <d:mn>2</d:mn> </d:mrow> </d:msub> </d:math> band as the thickness of the <e:math xmlns:e="http://www.w3.org/1998/Math/MathML"> <e:mrow> <e:mi>LaNi</e:mi> <e:msub> <e:mi mathvariant="normal">O</e:mi> <e:mn>3</e:mn> </e:msub> </e:mrow> </e:math> layer is decreased to a single unit cell, indicating a stronger correlation effect for the former upon dimensional confinement. Dynamical mean-field theory calculations show an orbital-selective Mott transition largely due to the localization of <g:math xmlns:g="http://www.w3.org/1998/Math/MathML"> <g:msub> <g:mi>d</g:mi> <g:mrow> <g:mi>z</g:mi> <g:mn>2</g:mn> </g:mrow> </g:msub> </g:math> electrons along the <h:math xmlns:h="http://www.w3.org/1998/Math/MathML"> <h:mi>c</h:mi> </h:math> axis in the monolayer limit. This orbital-selective correlation effect underpins many macroscopic properties of nickelates, such as metal-to-insulator transition and superconductivity, where most theories are built upon a <i:math xmlns:i="http://www.w3.org/1998/Math/MathML"> <i:mrow> <i:msub> <i:mi>d</i:mi> <i:mrow> <i:mi>x</i:mi> <i:mn>2</i:mn> <i:mo>−</i:mo> <i:mi>y</i:mi> <i:mn>2</i:mn> </i:mrow> </i:msub> <i:mtext>–</i:mtext> <i:msub> <i:mi>d</i:mi> <i:mrow> <i:mi>z</i:mi> <i:mn>2</i:mn> </i:mrow> </i:msub> </i:mrow> </i:math> two-band model.

  PublisherOA PDFDOI

• Probing the Wannier function of Crystalline Solids with Angle‐Resolved Photoemission Spectroscopy (Adv. Mater. Interfaces 4/2025)

  Advanced Materials Interfaces · 2025-02-01

  articleOpen accessSenior author

  Wannier Wave Function Probe Angle-resolved photoemission spectroscopy (ARPES) has been a widely adopted technique to investigate surface and shallow interface electron energy-momentum dispersion. The cover picture of article 2400427 by Charles H. Ahn and co-workers, proposes a new way of using ARPES to reconstruct the electron wave function on crystalline surfaces, via the dipole-transition matrix element effect and spectral sum rule.

  PublisherOA PDFDOI

• Interlayer couplings in cuprates: Structural origins, analytical forms, and structural estimators

  Physical review. B./Physical review. B · 2025-04-01 · 1 citations

  articleSenior author

  We quantitatively identify the multiple distinct microscopic mechanisms contributing to effective interlayer couplings (EICs) by performing first-principle calculations for two prototype superconducting cuprate families, pristine and doped ${\mathrm{Bi}}_{2}{\mathrm{Sr}}_{2}{\mathrm{CaCuO}}_{2}{\mathrm{O}}_{8+x}$ and ${\mathrm{Pr}}_{x}{\mathrm{Y}}_{1\ensuremath{-}x}{\mathrm{Ba}}_{2}{\mathrm{Cu}}_{3}{\mathrm{O}}_{7}$. The major mechanisms are mediated by interlayer oxygen ${p}_{\ensuremath{\sigma}}\text{\ensuremath{-}}{p}_{\ensuremath{\sigma}}$ and ${p}_{z}\text{\ensuremath{-}}{p}_{z}$ hoppings as well as interlayer copper ${d}_{3{z}^{2}\ensuremath{-}{r}^{2}}$-oxygen ${p}_{\ensuremath{\sigma}}$ hoppings. Furthermore, we show how EICs are closely related to structural distortions such as layer bucklings and bond length changes. This allows us to provide analytical formulas that permit direct estimation of the key interatomic hoppings and the EICs based only on the crystal structure. Finally, we benchmark our method on ${\mathrm{YBa}}_{2}{\mathrm{Cu}}_{3}{\mathrm{O}}_{7}$ to estimate the strength and anisotropy of the EIC.

  PublisherDOI

Awards & honors

• US Patent App. No.: PCT/US2010/002642 (2010)