About

Professor Richard Averitt is a Professor of Physics at the University of California, San Diego since 2014. Prior to this, he served as an Adjunct Professor of Physics at Boston University from 2014 to 2016, Associate Professor from 2010 to 2013, and Assistant Professor from 2006 to 2010. Before his academic appointments, he was a Staff Scientist at Los Alamos National Laboratory from 2001 to 2006 and a Director's Postdoctoral Fellow there from 1999 to 2001. He earned his PhD in Applied Physics from Rice University in 1998. His research focuses on the optical and electronic properties of quantum materials. He utilizes time-resolved optical spectroscopy techniques spanning from the far-infrared through the visible spectrum to explore the fundamental properties of quantum materials, with an emphasis on their dynamics and control. Additionally, he has long-standing interests in metamaterials and plasmonics. His work aims to understand and manipulate the behavior of complex condensed matter systems using advanced spectroscopic methods.

Research topics

• Physics
• Optics
• Optoelectronics
• Chemistry
• Computational physics
• Materials science

Selected publications

• Subgap pumping of antiferromagnetic Mott insulators: photoexcitation mechanisms and applications

  Reports on Progress in Physics · 2026-05-19

  preprintOpen access

  We study the behavior of the 2D repulsive Hubbard model on a square lattice at half filling, under strong driving with ac electric fields, by employing a time-dependent Gaussian variational approach. Within the same theoretical framework, we analytically obtain the conventional Keldysh crossover between multiphoton and tunneling photoexcitation mechanisms, as well as two new regimes beyond the Keldysh paradigm. We discuss how dynamical renormalization of the Mott-Hubbard gap feeds back into the photoexcitation process, modulating the carrier generation rate in real time. The momentum distribution of quasiparticle excitations immediately after the drive is calculated, and shown to contain valuable information about the generation mechanism. Finally, we discuss experimental probing of the pump-induced nonequilibrium electronic state.

  PublisherDOI

• Reconfigurable Quasi‐BIC Terahertz Metasurfaces Through MEMS‐Induced Symmetry Breaking (Advanced Optical Materials 9/2026)

  Advanced Optical Materials · 2026-03-01

  article

  Reconfigurable Quasi-BIC Terahertz Metasurfaces The cover image depicts a MEMS-enabled bimaterial cantilever metasurface supporting reconfigurable terahertz quasi–bound states in the continuum (quasi-BICs) via controlled symmetry breaking. In-plane mirror symmetry is broken through lateral resonator asymmetry, while MEMS-actuated cantilever tilting introduces dynamic out-of-plane asymmetry. Together, these mechanisms enable independent control of radiative and intrinsic losses, allowing active tuning of resonance linewidth and quality factor. More details can be found in the Research Article by Richard D. Averitt, Xin Zhang, and co-workers (DOI: 10.1002/adom.202503164).

  PublisherDOI

• Reconfigurable Quasi‐BIC Terahertz Metasurfaces Through MEMS‐Induced Symmetry Breaking

  Advanced Optical Materials · 2025-12-26

  articleCorresponding

  Abstract Symmetry‐protected bound states in the continuum (BICs) support high‐quality factor (Q) resonances. As a result, realizing tunable devices based on these states requires approaches that break the symmetry. Tunable mode leakage in terahertz BIC metasurfaces is demonstrated through structural symmetry breaking of an in‐plane mirror symmetry. Specifically, a leaky quasi‐BIC mode is created through the introduction of lateral asymmetry of the in‐plane resonator geometry and through asymmetric out‐of‐plane tilting using MEMS cantilever actuation. This provides fine‐tuned and reconfigurable control of the radiative leakage. Although out‐of‐plane deformation can, in principle, induce a BIC‐to‐quasi‐BIC transition, the study focuses on quasi‐BIC‐to‐quasi‐BIC modulation in order to clearly demonstrate leakage control and to facilitate modal analysis. Experimental measurements supported with full‐wave simulations and coupled‐mode theory (CMT) reveal distinct leakage and mode behavior for in‐plane and out‐of‐plane symmetry breaking. Importantly, control experiments using symmetrically tilted cantilevers confirm that radiative leakage to the far‐field arises from symmetry breaking rather than deformation alone. The dual symmetry‐breaking approach enables control over radiative and intrinsic loss through in‐plane and out‐of‐plane symmetry breaking, providing a robust and scalable route toward reconfigurable high‐Q terahertz metasurfaces.

  PublisherDOI

• Terahertz nonlinear and parametric dynamics in quantum materials

  2025-09-17

  article1st authorCorresponding

  Coherent terahertz pulses are a powerful probe of low-energy electrodynamics in quantum materials. This includes materials such as superconductors and charge density wave materials since ~0.1-10 THz is the appropriate energy scale to access electrodynamic signatures associated with condensate responses. In this contribution, we focus on coherent coherent terahertz dynamics in the putative excitonic insulator tantalum nickel selenide (TNS). We observe a broad reflectivity enhancement (~0.5 - 7 THz) that serves as a reporter of a condensate-like behavior in TNS which is difficult to otherwise detect. More broadly, our results highlight that nonlinear terahertz techniques enable characterization of subtle interactions in quantum materials. In particular, quantum materials can exhibit strong nonlinear and parametric light-matter interactions that encode information the many-body interactions.

  PublisherDOI

• Picosecond volume expansion drives a later-time insulator–metal transition in a nano-textured Mott insulator

  Nature Physics · 2024-02-09 · 16 citations

  articleOpen access
  PublisherOA PDFDOI

• Nonresonant nonlinear magnonics in an antiferromagnet

  arXiv (Cornell University) · 2024-11-15

  preprintOpen accessSenior author

  Antiferromagnets exhibit rapid spin dynamics in a net zero magnetic background which enables novel spintronic applications and interrogation of many-body quantum phenomena. The layered antiferromagnet Sr$_2$IrO$_4$ hosts an exotic spin one-half Mott insulating state with an electronic gap arising from on-site Coulomb repulsion and strong spin-orbit coupling. This makes Sr$_2$IrO$_4$ an interesting candidate to interrogate dynamical attributes of the magnetic order using ultrafast laser pulses. We investigate the magnetization dynamics of Sr$_2$IrO$_4$ following circularly-polarized photoexcitation with below-gap mid-infrared (mid-IR -- 9 $μm$) and above-gap near-infrared (near-IR -- 1.3 $μm$) pulses. In both cases, we observe excitation of a zone-center coherent magnon mode featuring a 0.5 THz oscillation in the pump-induced Kerr-rotation signal. However, only below-gap excitation exhibits a helicity dependent response and linear (quadratic) scaling of the coherent magnon amplitude with excitation fluence (electric field). Moreover, below-gap excitation has a magnon generation efficiency that is at least two orders of magnitude greater in comparison to above-gap excitation. Our analysis indicates that the helicity dependence and enhanced generation efficiency arises from a unique one-photon two-magnon coupling mechanism for magnon generation. Thus, preferential spin-photon coupling without photoexcitation of electrons permits extremely efficient magnon generation. Our results reveal new possibilities for ultrafast control of antiferromagnets.

  PublisherOA PDFDOI

• Photonic time-crystalline behaviour mediated by phonon squeezing in Ta2NiSe5

  Nature Communications · 2024-04-29 · 8 citations

  articleOpen access

  Abstract Photonic time crystals refer to materials whose dielectric properties are periodic in time, analogous to a photonic crystal whose dielectric properties is periodic in space. Here, we theoretically investigate photonic time-crystalline behaviour initiated by optical excitation above the electronic gap of the excitonic insulator candidate Ta 2 NiSe 5 . We show that after electron photoexcitation, electron-phonon coupling leads to an unconventional squeezed phonon state, characterised by periodic oscillations of phonon fluctuations. Squeezing oscillations lead to photonic time crystalline behaviour. The key signature of the photonic time crystalline behaviour is terahertz (THz) amplification of reflectivity in a narrow frequency band. The theory is supported by experimental results on Ta 2 NiSe 5 where photoexcitation with short pulses leads to enhanced THz reflectivity with the predicted features. We explain the key mechanism leading to THz amplification in terms of a simplified electron-phonon Hamiltonian motivated by ab-initio DFT calculations. Our theory suggests that the pumped Ta 2 NiSe 5 is a gain medium, demonstrating that squeezed phonon noise may be used to create THz amplifiers in THz communication applications.

  PublisherOA PDFDOI

• Inhomogeneous Photosusceptibility of <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:msub><mml:mrow><mml:mrow><mml:mi>VO</mml:mi></mml:mrow></mml:mrow><mml:mn>2</mml:mn></mml:msub></mml:mrow></mml:math> Films at the Nanoscale

  Physical Review Letters · 2024-05-03 · 11 citations

  article

  Pump-probe nano-optical experiments were used to study the light-induced insulator to metal transition (IMT) in thin films of vanadium dioxide (VO_{2}), a prototypical correlated electron system. We show that inhomogeneous optical contrast is prompted by spatially uniform photoexcitation, indicating an inhomogeneous photosusceptibility of VO_{2}. We locally characterize temperature and time dependent variations of the photoexcitation threshold necessary to induce the IMT on picosecond timescales with hundred nanometer spatial resolution. We separately measure the critical temperature T_{L}, where the IMT onsets and the local transient electronic nano-optical contrast at the nanoscale. Our data reveal variations in the photosusceptibility of VO_{2} within nanoscopic regions characterized by the same critical temperature T_{L} where metallic domains can first nucleate.

  PublisherDOI

• Terahertz Metamaterial Renormalization of Superconducting Josephson Plasmons in La$_{1.85}$Sr$_{0.15}$CuO$_4$

  arXiv (Cornell University) · 2024-03-18

  preprintOpen accessSenior author

  We investigate light-matter coupling in the cuprate superconductor La$_{1.85}$Sr$_{0.15}$Cu0$_4$ (LSCO), accomplished by adhering metamaterial resonator arrays (MRAs) to a c-axis oriented single crystal. The resonators couple to the Josephson Plasma Mode (JPM) which manifests as a plasma edge in the terahertz reflectivity in the superconducting state. Terahertz reflectivity measurements at 10K reveal a renormalization of the JPM frequency, $ω_{jpm}$, from 1.7 THz for the bare crystal to $\sim$1 THz with the MRAs. With increasing temperature, the modified $ω_{jpm}$ redshifts as expected for decreasing superfluid density, vanishing above T$_{c}$. The modification of the electrodynamic response arises from resonator induced screening of the longitudinal polariton response, reminiscent of plasmon-phonon coupling in doped semiconductors. Modeling reveals that the electrodynamic response is fully interpretable using classical electromagnetism. Future studies will have to contend with the large effects we observe which could obscure subtle changes that may indicate cavity-based manipulation of superconductivity. Finally, we note that our MRA/LSCO structure is a tunable epsilon-near-zero (ENZ) metamaterial that exhibits a nonlinear response arising from the c-axis Josephson tunneling coupled with the local fields of the resonators.

  PublisherOA PDFDOI

• Probing and controlling dynamics in quantum materials with terahertz light waves

  2024-01-01

  article1st authorCorresponding

  Coherent terahertz waves enable investigations of nonlinear many-body dynamics in quantum materials. Our recent work in this area has focused on condensates in superconductors and excitonic insulators.

  PublisherDOI

Frequent coauthors

• Antoinette J. Taylor

  Center for Integrated Nanotechnologies

  167 shared

• Inge Dittmer

  Stanford University

  121 shared

• Ralf B. Wehrspohn

  Martin Luther University Halle-Wittenberg

  121 shared

• Zhiyuan Li

  121 shared

• Hatice Altug

  École Polytechnique Fédérale de Lausanne

  121 shared

• Sjef Öllers

  University of Illinois Urbana-Champaign

  121 shared

• Mark L. Brongersma

  Stanford University

  121 shared

• Peter Günter

  École Polytechnique Fédérale de Lausanne

  121 shared

Labs

• Averitt Research GroupPI

  Quantum materials, time-resolved optical spectroscopy, metamaterials, plasmonics

Education

• Other

  UC San Diego

  1991

• Ph.D., Applied Physics

  Rice University

  1998