About

Professor Jak Chakhalian is a member of the Department of Physics and Astronomy at Rutgers University, holding the Claud Lovelace Endowed Professorship of Physics. His research primarily involves the use of a High-Vacuum laser Molecular Beam Epitaxy (laser MBE) apparatus to deposit thin films on substrates by laser ablation of various targets. He utilizes techniques such as High-Pressure Reflection High-Energy Electron Diffraction (HP RHEED) to monitor and control epitaxial growth, enabling the systematic creation of artificial ultrathin films and superlattices with different growth parameters. His work focuses on controlling growth conditions to produce samples with atomic precision, which are used to explore novel quantum states and materials. Professor Chakhalian's group has contributed to the discovery of a new quantum state at the intersection of exotic materials and has used atomic engineering to realize a room temperature two-dimensional polar metal in superlattices. His research also extends to the development of synthetic quantum structures and the study of complex quantum phenomena in engineered materials.

Research topics

• Computer Science
• Artificial Intelligence
• Algorithm
• Physics
• Mathematics

Selected publications

• Ultrafast Terahertz Field Control of the Emergent Magnetic and Electronic Interactions at Oxide Interfaces

  Repository for Publications and Research Data (ETH Zurich) · 2026-01-05

  otherOpen access

  Ultrafast electric‐field control of emergent electronic and magnetic states at oxide interfaces offers exciting prospects for the development of the next generation of energy‐efficient devices. Here, it is demonstrated that the electronic structure and emergent ferromagnetic interfacial state in epitaxial LaNiO 3 /CaMnO 3 superlattices can be effectively controlled using intense, single‐cycle THz electric‐field pulses. A suite of advanced X‐ray spectroscopic techniques is employed to measure a detailed magneto‐optical profile and the thickness of the ferromagnetic interfacial layer. Then, a combination of time‐resolved and temperature‐dependent optical measurements is used to disentangle several correlated electronic and magnetic processes driven by ultrafast, high‐field THz pulses. Sub‐picosecond non‐equilibrium Joule heating of the electronic system is observed, ultrafast demagnetization of the ferromagnetic interfacial layer, and slower dynamics indicative of a change in the magnetic state of the superlattice due to the transfer of spin‐angular momentum to the lattice. These findings suggest a promising avenue for the efficient control of 2D ferromagnetic states at oxide interfaces using ultrafast electric‐field pulses.

  PublisherDOI

• Ultrafast Terahertz Field Control of the Emergent Magnetic and Electronic Interactions at Oxide Interfaces

  DESY Publication Database (PUBDB) (Deutsches Elektronen-Synchrotron) · 2025-01-01

  articleOpen access

  Ultrafast electric-field control of emergent electronic and magnetic states at oxide interfaces offers exciting prospects for the development of the next generation of energy-efficient devices. Here, it is demonstrated that the electronic structure and emergent ferromagnetic interfacial state in epitaxial LaNiO3/CaMnO3 superlattices can be effectively controlled using intense, single-cycle THz electric-field pulses. A suite of advanced X-ray spectroscopic techniques is employed to measure a detailed magneto-optical profile and the thickness of the ferromagnetic interfacial layer. Then, a combination of time-resolved and temperature-dependent optical measurements is used to disentangle several correlated electronic and magnetic processes driven by ultrafast, high-field THz pulses. Sub-picosecond non-equilibrium Joule heating of the electronic system is observed, ultrafast demagnetization of the ferromagnetic interfacial layer, and slower dynamics indicative of a change in the magnetic state of the superlattice due to the transfer of spin-angular momentum to the lattice. These findings suggest a promising avenue for the efficient control of 2D ferromagnetic states at oxide interfaces using ultrafast electric-field pulses.

  PublisherDOI

• Epitaxial Stabilization of a Pyrochlore Interface between Weyl Semimetal and Spin Ice

  Nano Letters · 2025-01-02 · 5 citations

  articleSenior authorCorresponding

  Pyrochlore materials are known for their exotic magnetic and topological phases arising from complex interactions among electron correlations, band topology, and geometric frustration. Interfaces between different pyrochlore crystals characterized by complex many-body ground states hold immense potential for novel interfacial phenomena due to the strong interactions between these phases. However, the realization of such interfaces has been severely hindered by limitations in material synthesis methods. In this study, we discover a robust synthesis method that produces the previously unexplored epitaxial pyrochlore interface between spin ice Dy2Ti2O7 and Weyl semimetal Eu2Ir2O7. The method relies on an ultrahigh supersaturation regime during deposition aided by directional IR-laser-driven thermal gradients, transforming amorphous covalent networks into nearly perfectly ordered, atomically sharp interfaces with a chemically ideal arrangement of ions. The novel pyrochlore interface enables the study of interactions between relativistic Weyl fermions and spin ice magnetic monopoles, opening a path to designing diverse pyrochlore interfaces.

  PublisherDOI

• Daniel Khomskii

  Physics Today · 2025-08-20

  article
  PublisherDOI

• Electronic anisotropy and rotational symmetry breaking at a Weyl semimetal/spin ice interface

  Science Advances · 2025-06-13 · 2 citations

  articleOpen accessSenior authorCorresponding

  In magnetic pyrochlore materials, the interplay of spin-orbit coupling, electronic correlations, and geometrical frustration gives rise to exotic quantum phases, including topological semimetals and spin ice. While these phases have been observed in isolation, the interface-driven phenomena emerging from their interaction have never been realized previously. Here, we report on the discovery of interfacial electronic anisotropy and rotational symmetry breaking at a heterostructure consisting of the Weyl semimetal Eu 2 Ir 2 O 7 and spin ice Dy 2 Ti 2 O 7 . Subjected to magnetic fields, we unveil a sixfold anisotropic transport response that is theoretically accounted by a Kondo-coupled heterointerface, where the spin ice’s field-tuned magnetism induces electron scattering in the Weyl semimetal’s topological Fermi-arc states. Furthermore, at elevated magnetic fields, we reveal a twofold anisotropic response indicative of the emergence of a symmetry-broken many-body state. This discovery showcases the potential of pyrochlore frustrated magnet/topological semimetal heterostructures in search of emergent interfacial phenomena.

  PublisherDOI

• Spectrally sharp magnetic excitations above the critical temperature in a frustrated Weyl semimetal

  Nature Communications · 2025-07-17 · 1 citations

  articleOpen accessSenior author

  The rare-earth α-pyrochlore iridates are a prospective class of conducting frustrated magnets where electronic correlations, large spin-orbit coupling, and geometrical frustration interplay, leading to a rich set of magnetic and electronic phases. Despite their intriguing properties, the magnetic order and excitations in this fundamental class of topological quantum materials remain poorly understood due to challenges in growing large single crystals and insufficient microscopic information on their temperature-dependent phases. Here, by combining state-of-the-art thin-film synthesis, resonant elastic and inelastic X-ray scattering, spin wave analysis, and dynamical spin susceptibility calculations, we unequivocally reveal the presence of spectrally sharp, gapped magnetic excitations in Y2Ir2O7 that surprisingly persist well above the Néel transition temperature, signaling the presence of a quasi-universal regime connected to fluctuations on frustrated lattices. This finding implies the existence of a highly unusual cooperative paramagnetic (CP) phase above the ordering temperature and offers an explanation for the puzzling high-temperature magnetic behavior observed across the family of metallic pyrochlore crystals. Understanding such magnetic excitations at technologically relevant temperatures opens up possibilities for novel topological spintronic devices. Cooperative paramagnetism refers to a strongly correlated state without long range magnetic order that occurs in frustrated magnetic systems between the Neel temperature and Curie-Weiss temperature. Here, using resonant elastic magnetic and inelastic x-ray scattering, Terilli et al find a spectrally sharp gapped magnetic excitations that persists above the Neel temperature in Y2Ir2O7, implying a cooperative paramagnetic phase.

  PublisherOA PDFDOI

• Large Topological Magnetic Optical Effects and Imaging of Antiferromagnetic Octupole Domains of an Altermagnet-like Weyl Semimetal Eu2Ir2O7

  Research Square · 2025-05-21

  preprintOpen accessSenior author
  PublisherOA PDFDOI

• Large Topological Magnetic Optical Effects and Imaging of Antiferromagnetic Octupole Domains of an Altermagnet-like Weyl Semimetal

  ArXiv.org · 2025-05-06

  preprintOpen access

  Pyrochlore iridates have attracted significant interest due to their complex phase behavior arising from the interplay among electron correlations, quantum metric in flat bands, geometrically frustrated lattices, and topology induced by strong spin-orbit coupling. In this study, we focus on Eu$_2$Ir$_2$O$_7$ thin films oriented along the (111) crystallographic direction. This quantum material, identified as an antiferromagnetic Weyl semimetal, exhibits a large anomalous Hall effect in transport experiments. Here we employ optical circular dichroism microscopy, to directly image ferroic octupole order and resolve all-in--all-out and all-out--all-in antiferromagnetic domains below the Néel temperature. Remarkably, despite the absence of a detectable net magnetic moment at zero applied magnetic field, we detected a large magnetic circular dichroism signal ($\sim 10^{-4}$) and Kerr effect ($\sim 10^{-4}$ radians) in zero magnetic field attributable to Berry curvature effects from Weyl nodes. Eu$_2$Ir$_2$O$_7$ is a non-collinear magnet with vanishing net moment and magnetic octupole order, similar to the recently proposed collinear d-wave altermagnets, allowing for magneto-optical responses and anomalous Hall effect. This finding likely represents the first demonstration of magnetic circular dichroism and Kerr effect in a topologically non-trivial quantum antiferromagnet with a vanishing net magnetization. Our work opens up the possibility of ultrafast domain switching in the terahertz frequency and the domain wall dynamics in the magnetic Weyl systems, which establishes the foundation for topological antiferromagnetic spintronics.

  PublisherOA PDFDOI

• Ultrafast Terahertz Field Control of the Emergent Magnetic and Electronic Interactions at Oxide Interfaces

  Advanced Materials · 2025-11-24 · 1 citations

  articleOpen access

  Abstract Ultrafast electric‐field control of emergent electronic and magnetic states at oxide interfaces offers exciting prospects for the development of the next generation of energy‐efficient devices. Here, it is demonstrated that the electronic structure and emergent ferromagnetic interfacial state in epitaxial LaNiO 3 /CaMnO 3 superlattices can be effectively controlled using intense, single‐cycle THz electric‐field pulses. A suite of advanced X‐ray spectroscopic techniques is employed to measure a detailed magneto‐optical profile and the thickness of the ferromagnetic interfacial layer. Then, a combination of time‐resolved and temperature‐dependent optical measurements is used to disentangle several correlated electronic and magnetic processes driven by ultrafast, high‐field THz pulses. Sub‐picosecond non‐equilibrium Joule heating of the electronic system is observed, ultrafast demagnetization of the ferromagnetic interfacial layer, and slower dynamics indicative of a change in the magnetic state of the superlattice due to the transfer of spin‐angular momentum to the lattice. These findings suggest a promising avenue for the efficient control of 2D ferromagnetic states at oxide interfaces using ultrafast electric‐field pulses.

  PublisherDOI

• Depth-Resolved Profile of the Interfacial Ferromagnetism in CaMnO₃/CaRuO₃ Superlattices

  Nano Letters · 2024-11-20 · 3 citations

  articleOpen access

  Emergent magnetic phenomena at interfaces represent a frontier in materials science, pivotal for advancing technologies in spintronics and magnetic storage. In this Letter, we utilize a suite of advanced X-ray spectroscopic and scattering techniques to investigate emergent interfacial ferromagnetism in oxide superlattices composed of antiferromagnetic CaMnO3 and paramagnetic CaRuO3. Our findings demonstrate that ferromagnetism exhibits an asymmetric profile and may extend beyond the interfacial layer into multiple unit cells of CaMnO3. Complementary density functional calculations reveal that the interfacial ferromagnetism is driven by the double exchange mechanism, facilitated by charge transfer from Ru to Mn ions. Additionally, defect chemistry, particularly the presence of oxygen vacancies, can play a crucial role in modifying the magnetic moments at the interface, possibly leading to the observed asymmetry between the top and bottom CaMnO3 interfacial magnetic layers. Our findings underscore the potential of manipulating interfacial ferromagnetism through point defect engineering.

  PublisherOA PDFDOI

Recent grants

• CAREER: Exploring Artificial Quantum Matter

  NSF · $411k · 2008–2013

Frequent coauthors

• M. Kareev

  Rutgers, The State University of New Jersey

  116 shared

• J. W. Freeland

  Argonne National Laboratory

  88 shared

• S. Middey

  Indian Institute of Science Bangalore

  70 shared

• Xiaoran Liu

  56 shared

• Yanwei Cao

  Chinese Academy of Sciences

  53 shared

• Jian Liu

  46 shared

• D. Meyers

  Oklahoma State University Oklahoma City

  44 shared

• Padraic Shafer

  Lawrence Berkeley National Laboratory

  36 shared

Labs

• KECK Center for Quantum MagnetismPI

Awards & honors

• Claud Lovelace Endowed Professor of Physics