About

Professor Jyoti Katoch is a principal investigator at the Katoch-Singh Lab, located in Wean Hall 6414. The research group led by Professor Katoch focuses on the field of low-dimensional solid state systems, exploring novel condensed matter systems and their atomically thin nanodevices. The group offers opportunities for graduate and undergraduate students to engage in advanced research areas including nanodevice fabrication, epitaxial material growth techniques, layer-by-layer assembly of van der Waals heterostructures, quantum magneto-transport, spintronics devices, optical and photo-emission spectroscopy, magnetization dynamics, and surface science techniques. Professor Katoch's lab actively recruits highly motivated and hard-working students interested in these cutting-edge topics in condensed matter physics.

Research topics

• Materials science
• Physics
• Condensed matter physics
• Quantum mechanics
• Nanotechnology
• Geometry
• Chemistry

Selected publications

• Visualization of Tunable Electronic Structure of Monolayer TaIrTe$_4$

  arXiv (Cornell University) · 2026-01-16

  preprintOpen accessSenior author

  Monolayer TaIrTe$_4$ has emerged as an attractive material platform to study intriguing phenomena related to topology and strong electron correlations. Recently, strong interactions have been demonstrated to induce strain and dielectric screening tunable topological phases such as quantum spin Hall insulator (QSHI), trivial insulator, higher-order topological insulator, and metallic phase, in the ground state of monolayer TaIrTe$_4$. Moreover, charge dosing has been demonstrated to convert the QSHI into a dual QSHI state. Although the band structure of monolayer TaIrTe$_4$ is central to interpreting its topological phases in transport experiments, direct experimental access to its intrinsic electronic structure has so far remained elusive. Here we report direct measurements of the monolayer TaIrTe$_4$ band structure using spatially resolved micro-angle-resolved photoemission spectroscopy (microARPES) with micrometre-scale resolution. The observed dispersions show quantitative agreement with density functional theory calculations using the Heyd-Scuseria-Ernzerhof hybrid functional, establishing the insulating ground state and revealing no evidence for strong electronic correlations. We further uncover a pronounced electron-hole asymmetry in the doping response. Whereas hole doping is readily induced by electrostatic gating, attempts to introduce electrons via gating or alkali metal deposition do not yield a rigid upward shift of the Fermi level. Fractional charge calculations demonstrate that added electrons instead drive band renormalization and shrink the band gap. Taken together, our experimental and theoretical results identify the microscopic mechanism by which induced charges reshape the band topology of monolayer TaIrTe$_4$, showing that doping can fundamentally alter the electronic structure beyond the rigid band behaviour that is typically assumed.

  PublisherDOI

• Visualization of Tunable Electronic Structure of Monolayer TaIrTe$_4$

  ArXiv.org · 2026-01-16

  articleOpen accessSenior author

  Monolayer TaIrTe$_4$ has emerged as an attractive material platform to study intriguing phenomena related to topology and strong electron correlations. Recently, strong interactions have been demonstrated to induce strain and dielectric screening tunable topological phases such as quantum spin Hall insulator (QSHI), trivial insulator, higher-order topological insulator, and metallic phase, in the ground state of monolayer TaIrTe$_4$. Moreover, charge dosing has been demonstrated to convert the QSHI into a dual QSHI state. Although the band structure of monolayer TaIrTe$_4$ is central to interpreting its topological phases in transport experiments, direct experimental access to its intrinsic electronic structure has so far remained elusive. Here we report direct measurements of the monolayer TaIrTe$_4$ band structure using spatially resolved micro-angle-resolved photoemission spectroscopy (microARPES) with micrometre-scale resolution. The observed dispersions show quantitative agreement with density functional theory calculations using the Heyd-Scuseria-Ernzerhof hybrid functional, establishing the insulating ground state and revealing no evidence for strong electronic correlations. We further uncover a pronounced electron-hole asymmetry in the doping response. Whereas hole doping is readily induced by electrostatic gating, attempts to introduce electrons via gating or alkali metal deposition do not yield a rigid upward shift of the Fermi level. Fractional charge calculations demonstrate that added electrons instead drive band renormalization and shrink the band gap. Taken together, our experimental and theoretical results identify the microscopic mechanism by which induced charges reshape the band topology of monolayer TaIrTe$_4$, showing that doping can fundamentally alter the electronic structure beyond the rigid band behaviour that is typically assumed.

  PublisherOA PDF

• Ultrafast Light-Induced Magnetoelectric Effect in van der Waals Magnetic Semiconductor Heterostructures

  ArXiv.org · 2026-04-21

  articleOpen access

  Atomic-scale heterostructures of van der Waals (vdW) magnets and semiconductors provide a unique environment for exploring magnetic dynamics. In contrast to typical photothermal excitation of precessional magnetization dynamics by a pump laser pulse, we find that ultrafast optical excitation of a WS$_2$/CrGeTe$_3$ (CGT) bilayer produces an opposite sign of magnetic torque compared to an isolated CGT film. Experimental observations by time-resolved magneto-optic Kerr effect (TR-MOKE) and theoretical analysis by density functional theory (DFT) and Landau-Lifshitz-Gilbert (LLG) simulations support a mechanism in which charge transfer of photoexcited carriers across the interface alters the perpendicular magnetic anisotropy, which in turn generates a torque on the magnetic layer to trigger precessional magnetization dynamics. These results provide new avenues for ultrafast manipulation of magnetization in vdW heterostructures with type-II band alignments. Lastly, we show that optically-generated spin currents from WS$_2$ into CGT can also trigger precessional dynamics via angular momentum transfer.

  PublisherOA PDF

• Ultrafast Light-Induced Magnetoelectric Effect in van der Waals Magnetic Semiconductor Heterostructures

  arXiv (Cornell University) · 2026-04-21

  preprintOpen access

  Atomic-scale heterostructures of van der Waals (vdW) magnets and semiconductors provide a unique environment for exploring magnetic dynamics. In contrast to typical photothermal excitation of precessional magnetization dynamics by a pump laser pulse, we find that ultrafast optical excitation of a WS$_2$/CrGeTe$_3$ (CGT) bilayer produces an opposite sign of magnetic torque compared to an isolated CGT film. Experimental observations by time-resolved magneto-optic Kerr effect (TR-MOKE) and theoretical analysis by density functional theory (DFT) and Landau-Lifshitz-Gilbert (LLG) simulations support a mechanism in which charge transfer of photoexcited carriers across the interface alters the perpendicular magnetic anisotropy, which in turn generates a torque on the magnetic layer to trigger precessional magnetization dynamics. These results provide new avenues for ultrafast manipulation of magnetization in vdW heterostructures with type-II band alignments. Lastly, we show that optically-generated spin currents from WS$_2$ into CGT can also trigger precessional dynamics via angular momentum transfer.

  PublisherDOI

• Magnetization Dependent In-plane Anomalous Hall Effect in a Low-dimensional System

  ArXiv.org · 2025-05-11

  preprintOpen access

  Anomalous Hall Effect (AHE) response in magnetic systems is typically proportional to an out-of-plane magnetization component because of the restriction imposed by system symmetries, which demands that the magnetization, applied electric field, and induced Hall current are mutually orthogonal to each other. Here, we report experimental realization of an unconventional form of AHE in a low-dimensional heterostructure, wherein the Hall response is not only proportional to the out-of-plane magnetization component but also to the in-plane magnetization component. By interfacing a low-symmetry topological semimetal (TaIrTe4) with the ferromagnetic insulator (Cr2Ge2Te6), we create a low-dimensional magnetic system, where only one mirror symmetry is preserved. We show that as long as the magnetization has a finite component in the mirror plane, this last mirror symmetry is broken, allowing the emergence of an AHE signal proportional to in-plane magnetization. Our experiments, conducted on multiple devices, reveal a gate-voltage-dependent AHE response, suggesting that the underlying mechanisms responsible for the Hall effect in our system can be tuned via electrostatic gating. A minimal microscopic model constrained by the symmetry of the heterostructure shows that both interfacial spin-orbit coupling and time-reversal symmetry breaking via the exchange interaction from magnetization are responsible for the emergence of the in-plane AHE. Our work highlights the importance of system symmetries and exchange interaction in low-dimensional heterostructures for designing novel and tunable Hall effects in layered quantum systems.

  PublisherOA PDFDOI

• Direct visualization of gate-tunable flat bands in twisted double bilayer graphene

  ArXiv.org · 2025-10-22

  preprintOpen accessSenior author

  The symmetry-broken correlated states in twisted double bilayer graphene (TDBG) can be tuned via several external knobs, including twist angle, displacement field, and carrier density. However, a direct, momentum-resolved characterization of how these parameters reshape the flat-band structure remains limited. In this study, we employ micro focused angle-resolved photoemission spectroscopy to investigate the flat-band dispersion of TDBG at a twist angle of 1.6, systematically varying the displacement field and carrier density via electrostatic gating. We directly observe multiple flat moir'e minibands near charge neutrality, including a flat remote valence band residing below the low-energy flat-band manifold. Furthermore, the dominant Coulomb repulsive energy over the flat- band bandwidth suggests favorable conditions for the emergence of interaction-driven correlated phenomena in TDBG. These findings establish that the formation and evolution of flat bands in TDBG arises from the interplay between the electron filling and the displacement field.

  PublisherOA PDFDOI

• Unconventional unidirectional magnetoresistance in heterostructures of a topological semimetal and a ferromagnet

  Nature Materials · 2025-03-21 · 13 citations

  article
  PublisherDOI

• Quantum Sensing of Spin Dynamics Using Boron-Vacancy Centers in Hexagonal Boron Nitride

  Physical Review Letters · 2024-10-17 · 13 citations

  article

  Spin defects embedded in solid-state systems are appealing for quantum sensing of materials and for quantum science and engineering. The spin-sensitive photoluminescence of optically active spin defects in Van der Waals based materials, such as the boron-vacancy (V_{B}^{-}) center in hexagonal boron nitride, enables its application as a quantum sensor to detect weak, spatially localized magnetic static and dynamic fields. However, the utility of V_{B}^{-} centers to probe spin dynamics in magnetic systems has yet to be demonstrated; this is essential to establish the V_{B}^{-} as a modular sensing platform that can be seamlessly integrated with emergent quantum materials to probe a wide range of static and dynamic phenomena. Here, we use V_{B}^{-} centers to experimentally probe uniform mode magnon dynamics and optically perform ferromagnetic resonance spectroscopy on a thin magnetic film.

  PublisherDOI

• Revealing the EuCd₂As₂ Semiconducting Band Gap via n-Type La-Doping

  Chemistry of Materials · 2024-07-24 · 5 citations

  preprintOpen access

  EuCd2As2 has attracted considerable interest as one of the few magnetic Weyl semimetal candidate materials, although recently, there have been emerging reports that claim it to have a semiconducting electronic structure. To resolve this debate, we established the growth of n-type EuCd2As2 crystals to directly visualize the nature of the conduction band using angle-resolved photoemission spectroscopy (ARPES). We show that La-doping leads to n-type transport signatures in both thermopower and Hall effect measurements, in crystals with n-type doping levels of 2–6 × 1017 cm–3. Both p- and n-type-doped samples exhibit antiferromagnetic ordering at 9 K. ARPES experiments at 6 K clearly show the presence of the conduction band minimum at 0.8 eV above the valence band maximum, which is further corroborated by the observation of a 0.71–0.72 eV band gap in room temperature diffuse reflectance absorbance measurements. Together, these findings unambiguously show that EuCd2As2 is indeed a semiconductor with a substantial band gap and not a topological semimetal.

  PublisherOA PDFDOI

• Optically induced trion formation and its control in a MoS₂/graphene van der Waals heterostructure

  Nanoscale · 2024-01-01 · 6 citations

  article

  Monolayer 2D transition metal dichalcogenides are sensitive to charge transfer leading to modified optoelectronic properties.

  PublisherDOI

Frequent coauthors

• Simranjeet Singh

  Carnegie Mellon University

  92 shared

• Søren Ulstrup

  Aarhus University

  73 shared

• Eli Rotenberg

  Lawrence Berkeley National Laboratory

  69 shared

• Chris Jozwiak

  69 shared

• Aaron Bostwick

  68 shared

• Roland J. Koch

  Lawrence Berkeley National Laboratory

  67 shared

• Ryan Muzzio

  National Renewable Energy Laboratory

  64 shared

• B. T. Jonker

  61 shared

Labs

• KATOCH-SINGH LABPI

Education

• Ph.D.

  University of Central Florida

  2014

• B.S., Physics, Mathematics and Chemistry

  Panjab University (India)

  2004

Awards & honors

• DOE Early Career Research Award (2019)