About

Zhi-Xun Shen is the Paul Pigott Professor in the Physical Sciences at Stanford University, where he holds positions in Applied Physics, Physics, and Photon Science. His research focuses on condensed matter physics, particularly quantum many-body physics in strongly-correlated electron systems and other novel quantum systems. His work includes the study of high-temperature superconductors, Fe-pnictide superconductors, topological quantum matter, density wave materials, and quantum systems with constrained dimensions such as monolayer superconductivity and transition metal dichalcogenides. Shen employs high-resolution angle-resolved photo-emission spectroscopy as his main investigative tool, complemented by other photon-based techniques like resonance x-ray scattering, inelastic x-ray scattering, and microwave impedance microscopy. His research also involves developing and optimizing synchrotron radiation-based photoemission experiments, including spin-resolved spectroscopy and time-resolved photo-emission using UV lasers, as well as soft x-ray scattering using facilities like the LCLS. Additionally, Shen's work in nanoscience and quantum engineering includes developing AFM-based near-field microwave microscopy to measure electrical properties at nanometer resolution, studying physics and material science problems at mesoscopic length scales, and investigating the physics and applications of diamondoids and related materials, which combine diamond structures with nanometer-scale properties.

Research topics

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

Selected publications

• Thermal Hall conductivity of electron-doped cuprates

  Physical review. B./Physical review. B · 2022 · 21 citations

  • Condensed matter physics
  • Physics
  • Quantum mechanics

  Measurements of the thermal Hall conductivity in hole-doped cuprates have shown that phonons acquire chirality in a magnetic field both in the pseudogap phase and in the Mott insulator state. The microscopic mechanism at play is still unclear. A number of theoretical proposals are being considered including skew scattering of phonons by various defects, the coupling of phonons to spins, and a state of loop-current order with the appropriate symmetries, but more experimental information is required to constrain theoretical scenarios. Here we present our study of the thermal Hall conductivity ${\ensuremath{\kappa}}_{\mathrm{xy}}$ in the electron-doped cuprates ${\mathrm{Nd}}_{2\ensuremath{-}x}{\mathrm{Ce}}_{x}{\mathrm{CuO}}_{4}$ and ${\mathrm{Pr}}_{2\ensuremath{-}x}{\mathrm{Ce}}_{x}{\mathrm{CuO}}_{4}$ for dopings across the phase diagram, from $x=0$ in the insulating antiferromagnetic phase up to $x=0.17$ in the metallic phase above optimal doping. We observe a large negative thermal Hall conductivity at all dopings in both materials. Since heat conduction perpendicular to the ${\mathrm{CuO}}_{2}$ planes is dominated by phonons, the large thermal Hall conductivity we observe in electron-doped cuprates for a heat current in that direction must also be due to phonons, as in hole-doped cuprates. However, the degree of chirality, measured as the ratio $|{\ensuremath{\kappa}}_{\mathrm{xy}}/{\ensuremath{\kappa}}_{\mathrm{xx}}|$ where ${\ensuremath{\kappa}}_{\mathrm{xx}}$ is the longitudinal thermal conductivity, is much larger in the electron-doped cuprates. We discuss various factors that may be involved in the mechanism that confers chirality to phonons in cuprates, including short-range spin correlations.

  PublisherOA PDFDOI

• Evidence for quantum spin liquid behaviour in single-layer 1T-TaSe2 from scanning tunnelling microscopy

  Nature Physics · 2021 · 159 citations

  • Condensed matter physics
  • Physics
  DOI

• Quantum Photonic Interface for Tin-Vacancy Centers in Diamond

  Physical Review X · 2021 · 106 citations

  • Physics
  • Condensed matter physics
  • Optoelectronics

  The realization of quantum networks critically depends on establishing efficient, coherent light-matter interfaces. Optically active spins in diamond have emerged as promising quantum nodes based on their spin-selective optical transitions, long-lived spin ground states, and potential for integration with nanophotonics. Tin-vacancy (SnV -) centers in diamond are of particular interest because they exhibit narrow-linewidth emission in nanostructures and possess long spin coherence times at temperatures above 1 K. However, a nanophotonic interface for SnV -centers has not yet been realized. Here, we report cavity enhancement of the emission of SnV -centers in diamond. We integrate SnV -centers into onedimensional photonic crystal resonators and observe a 40-fold increase in emission intensity. The Purcell factor of the coupled system is 25, resulting in a channeling of the majority of photons (90%) into the cavity mode. Our results pave the way for the creation of efficient, scalable spin-photon interfaces based on SnV -centers in diamond.

  DOI

• Imaging spinon density modulations in a 2D quantum spin liquid

  arXiv (Cornell University) · 2020 · 5 citations

  • Condensed matter physics
  • Physics
  • Quantum mechanics

  Two-dimensional triangular-lattice antiferromagnets are predicted under some conditions to exhibit a quantum spin liquid ground state whose low-energy behavior is described by a spinon Fermi surface. Directly imaging the resulting spinons, however, is difficult due to their fractional, chargeless nature. Here we use scanning tunneling spectroscopy to image spinon density modulations arising from a spinon Fermi surface instability in single-layer 1T-TaSe$_2$, a two-dimensional Mott insulator. We first demonstrate the existence of localized spins arranged on a triangular lattice in single-layer 1T-TaSe$_2$ by contacting it to a metallic 1H-TaSe$_2$ layer and measuring the Kondo effect. Subsequent spectroscopic imaging of isolated, single-layer 1T-TaSe$_2$ reveals long-wavelength modulations at Hubbard band energies that reflect spinon density modulations. This allows direct experimental measurement of the spinon Fermi wavevector, in good agreement with theoretical predictions for a 2D quantum spin liquid. These results establish single-layer 1T-TaSe$_2$ as a new platform for studying novel two-dimensional quantum-spin-liquid phenomena.

  PublisherOA PDF

• Synergistic enhancement of electrocatalytic CO2 reduction to C2 oxygenates at nitrogen-doped nanodiamonds/Cu interface

  Nature Nanotechnology · 2020 · 261 citations

  • Materials science
  • Chemical engineering
  • Nanotechnology
  DOI

• Strong correlations and orbital texture in single-layer 1T-TaSe2

  Nature Physics · 2020 · 225 citations

  • Condensed matter physics
  • Physics
  • Quantum mechanics
  DOI

Recent grants

• Scanning Microwave Microscopy Study of Complex Quantum Matter

  NSF · $390k · 2009–2013

• Microwave Impedance Microscopy Study of Topological Structures of Quantum Materials

  NSF · $860k · 2013–2019

Frequent coauthors

• Alex Frañó

  University of California, San Diego

  8 shared

• S. W. Huang

  8 shared

• Yi Zhang

  King University

  8 shared

• Z. Hussain

  Hohai University

  7 shared

• Miguel M. Ugeda

  Donostia International Physics Center

  6 shared

• Feng Wang

  University of California, Berkeley

  6 shared

• Michael F. Crommie

  Kavli Energy NanoScience Institute

  6 shared

• Yu-Cheng Shao

  Lawrence Berkeley National Laboratory

  6 shared

Labs

• Shen LaboratoryPI

Education

• Ph.D., Applied Physics

  Stanford University

  1994

• B.S., Physics

  University of Science and Technology of China

  1989

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