About

Javier D. Sanchez-Yamagishi is an Assistant Professor of Physics and Astronomy at UCI. His research focuses on condensed matter physics, specifically on 2-dimensional materials such as graphene, electronic transport, nanoscale magnetometry, and quantum phenomena. He completed his Ph.D. at the Massachusetts Institute of Technology in 2015 and was a Postdoctoral Fellow at the Harvard Quantum Optics Center. His educational background includes a B.S. in Physics from Rutgers, The State University of New Jersey, obtained in 2008. His work involves exploring the electronic and magnetic properties of low-dimensional materials, contributing to the understanding of quantum effects at the nanoscale.

Research topics

• Materials science
• Condensed matter physics
• Physics
• Nanotechnology
• Optoelectronics

Selected publications

• Van der Waals injection-molded crystals

  npj 2D Materials and Applications · 2025-12-11 · 1 citations

  articleOpen accessSenior author

  Abstract Shaping low-dimensional crystals into precise geometries with low disorder is an outstanding challenge. Here, we present a method to grow single crystals of arbitrary geometry within van der Waals (vdW) materials. By injecting molten material between atomically flat vdW layers within an SiO 2 mold, we produce ultraflat and thin crystals of bismuth, tin, and indium that are shaped as hallbars, rings, and nanowires. The crystals are grown fully encapsulated in hexagonal boron nitride, a vdW material, providing protection from oxidation. Varying the depth of the mold allows us to control the crystal thickness from ten to a hundred nanometers. Structural measurements demonstrate large single crystals encompassing the entire mold geometry, while transport measurements show reduced disorder scattering. This approach offers a means to produce complex single-crystal nanostructures without the disorder introduced by post-growth nanofabrication.

  PublisherOA PDFDOI

• Metals squeezed to thickness of just two atoms

  Nature · 2025-03-12 · 3 citations

  article1st authorCorresponding
  PublisherDOI

• Van der Waals vacuum cells for confining atoms and crystals

  2025-03-19

  article1st authorCorresponding
  PublisherDOI

• Manipulating moires by controlling heterostrain in van der Waals devices

  arXiv (Cornell University) · 2024-09-11

  preprintOpen accessSenior author

  Van der Waals (vdW) moires offer tunable superlattices that can strongly manipulate electronic properties. We demonstrate the in-situ manipulation of moire superlattices via heterostrain control in a vdW device. By straining a graphene layer relative to its hexagonal boron nitride substrate, we modify the shape and size of the moire. Our sliding-based technique achieves uniaxial heterostrain values exceeding 1%, resulting in distorted moires that are larger than those achievable without strain. The stretched moire is evident in transport measurements, resulting in shifted superlattice resistance peaks and Landau fans consistent with an enlarged superlattice unit cell. Electronic structure calculations reveal how heterostrain shrinks and distorts the moire Brillouin zone, resulting in a reduced electronic bandwidth as well as the appearance of highly anisotropic and quasi-1-dimensional Fermi surfaces. Our heterostrain control approach opens a wide parameter space of moire lattices to explore beyond what is possible by twist angle control alone.

  PublisherOA PDFDOI

• Manipulating Moirés by Controlling Heterostrain in van der Waals Devices

  Nano Letters · 2024-11-25 · 7 citations

  articleSenior authorCorresponding

  manipulation of moiré superlattices via heterostrain control in a vdW device. By straining a graphene layer relative to its hexagonal boron nitride substrate, we modify the shape and size of the moiré. Our sliding-based technique achieves uniaxial heterostrain values exceeding 1%, resulting in distorted moirés values that are larger than those achievable without strain. The stretched moiré is evident in transport measurements, resulting in shifted superlattice resistance peaks and Landau fans, consistent with an enlarged superlattice unit cell. Electronic structure calculations reveal how heterostrain shrinks and distorts the moiré Brillouin zone, resulting in a reduced electronic bandwidth as well as the appearance of highly anisotropic and quasi-one-dimensional Fermi surfaces. Our heterostrain control approach opens a wide parameter space of moiré lattices to explore beyond what is possible by twist angle control alone.

  PublisherDOI

• Electrically driven amplification of terahertz acoustic waves in graphene

  Nature Communications · 2024-03-21 · 15 citations

  articleOpen accessSenior author

  In graphene devices, the electronic drift velocity can easily exceed the speed of sound in the material at moderate current biases. Under these conditions, the electronic system can efficiently amplify acoustic phonons, leading to an exponential growth of sound waves in the direction of the carrier flow. Here, we show that such phonon amplification can significantly modify the electrical properties of graphene devices. We observe a superlinear growth of the resistivity in the direction of the carrier flow when the drift velocity exceeds the speed of sound - resulting in a sevenfold increase over a distance of 8 µm. The resistivity growth is observed at carrier densities away from the Dirac point and is enhanced at cryogenic temperatures. We develop a theoretical model for the resistivity growth due to the electrical amplification of acoustic phonons - reaching frequencies up to 2.2 THz - where the wavelength is controlled by gate-tunable transitions across the Fermi surface. These findings provide a route to on-chip high-frequency sound generation and detection in the THz frequency range.

  PublisherOA PDFDOI

• Exceptional electronic transport and quantum oscillations in thin bismuth crystals grown inside van der Waals materials

  Nature Materials · 2024-05-13 · 30 citations

  articleOpen accessSenior author
  PublisherOA PDFDOI

• Controllable strain-driven topological phase transition and dominant surface-state transport in HfTe5

  Nature Communications · 2024-01-06 · 18 citations

  articleOpen access

  Abstract The fine-tuning of topologically protected states in quantum materials holds great promise for novel electronic devices. However, there are limited methods that allow for the controlled and efficient modulation of the crystal lattice while simultaneously monitoring the changes in the electronic structure within a single sample. Here, we apply significant and controllable strain to high-quality HfTe 5 samples and perform electrical transport measurements to reveal the topological phase transition from a weak topological insulator phase to a strong topological insulator phase. After applying high strain to HfTe 5 and converting it into a strong topological insulator, we found that the resistivity of the sample increased by 190,500% and that the electronic transport was dominated by the topological surface states at cryogenic temperatures. Our results demonstrate the suitability of HfTe 5 as a material for engineering topological properties, with the potential to generalize this approach to study topological phase transitions in van der Waals materials and heterostructures.

  PublisherOA PDFDOI

• Electrically-driven amplification of terahertz acoustic waves in graphene

  Institutional Repositories DataBase (IRDB) · 2023-10-18

  preprintOpen accessSenior author

  In graphene devices, the electronic drift velocity can easily exceed the speed of sound in the material at moderate current biases. Under this condition, the electronic system can efficiently amplify acoustic phonons, leading to the exponential growth of sound waves in the direction of the carrier flow. Here, we demonstrate that such phonon amplification can significantly modify the electrical properties of graphene devices. We observe a super-linear growth of the resistivity in the direction of the carrier flow when the drift velocity exceeds the speed of sound, causing up to a 7 times increase over 8 micrometers. The resistance growth is observable for carrier densities away from the Dirac point and is enhanced at cryogenic temperatures. These observations are explained by a theoretical model for the electrical-amplification of acoustic phonons, which reach frequencies up to 2.2 terahertz with the nanoscale wavelength set by gate-tunable ~kF transitions across the Fermi surface. These findings offer a route to high-frequency on-chip sound generation and detection, which can be used to modulate and probe electronic physics in van der Waals heterostructures in the terahertz frequency range.

  PublisherDOI

• Mechanically reconfigurable van der Waals devices via low-friction gold sliding

  Science Advances · 2023-04-07 · 16 citations

  articleOpen accessSenior authorCorresponding

  Interfaces of van der Waals (vdW) materials, such as graphite and hexagonal boron nitride (hBN), exhibit low-friction sliding due to their atomically flat surfaces and weak vdW bonding. We demonstrate that microfabricated gold also slides with low friction on hBN. This enables the arbitrary post-fabrication repositioning of device features both at ambient conditions and in situ to a measurement cryostat. We demonstrate mechanically reconfigurable vdW devices where device geometry and position are continuously tunable parameters. By fabricating slidable top gates on a graphene-hBN device, we produce a mechanically tunable quantum point contact where electron confinement and edge-state coupling can be continuously modified. Moreover, we combine in situ sliding with simultaneous electronic measurements to create new types of scanning probe experiments, where gate electrodes and even entire vdW heterostructure devices can be spatially scanned by sliding across a target.

  PublisherOA PDFDOI

Recent grants

• CAREER: Manipulating Topology and Correlations in 2D Heterostructures by Dynamic Structural Control

  NSF · $735k · 2021–2027

Frequent coauthors

• Pablo Jarillo‐Herrero

  45 shared

• Kenji Watanabe

  National Institute for Materials Science

  42 shared

• Takashi Taniguchi

  36 shared

• Jing Kong

  Beijing Aerospace Flight Control Center

  12 shared

• Vitor R. Manfrinato

  10 shared

• Hongkun Park

  Harvard University

  10 shared

• Jason Luo

  10 shared

• Leonardo C. Campos

  Universidade Federal de Minas Gerais

  10 shared

Labs

• Condensed Matter PhysicsPI

Education

• Phd, Physics

  Massachusetts Institute of Technology

  2015