More Like this

1. Analysis and applications of a heralded electron source

   https://doi.org/10.1088/1367-2630/ada8d0  

   Koppell, Stewart; Simonaitis, John; Krielaart, Maurice; Berggren, Karl_K; Keathley, Phillip_D; Putnam, William (January 2025, New Journal of Physics)

   Abstract We analytically describe the noise properties of a heralded electron source made from a standard electron gun, a weak photonic coupler, a single photon counter, and an electron energy filter. We describe the sub-Poissonian statistics of the source, the engineering requirements for efficient heralding, and several potential applications. We use simple models of electron beam processes to demonstrate advantages which are situational, but potentially significant in electron lithography and scanning electron microscopy. 

   more » « less
2. Superconductor to exciton condensate transition in a model copper-oxide material

   https://doi.org/10.1088/1367-2630/ad9cb4  

   Schouten, Anna_O; Sager-Smith, LeeAnn_M; Mazziotti, David_A (December 2024, New Journal of Physics)

   Abstract Superconductivity and exciton condensation are fundamental phenomena in condensed matter physics, associated with the condensation of electron–electron and electron–hole pairs, respectively, into coherent quantum states. In this study, we present evidence of a superconductor to exciton condensate transition within the context of the three-band Hubbard model of copper-oxide-like materials. As the electron–electron repulsion increases, the superconducting phase is superseded by exciton condensation. In support of theoretical predictions—not yet realized experimentally—we observe the coexistence of the two condensates in the vicinity of the transition where the quantum states become a superposition of electron–electron and electron–hole condensates. Coexistence is rigorously computed from large eigenvalues and their eigenvectors in both the two-electron reduced density matrix (2-RDM) and the particle-hole RDM, which we obtain from a direct variational ground-state energy minimization with respect to the 2-RDM by semidefinite programming. We further discern that adjacentdorbitals and interveningporbitals facilitate electron–electron pairing between copper orbitals, thereby supporting the superexchange mechanism for superconductivity. These observations suggest the feasibility of witnessing a superconductor to exciton condensate transition in copper-oxide analogs, bearing significant implications for identifying materials conducive to efficient transport processes. 

   more » « less
3. Parametric dependence of hot electron relaxation timescales on electron-electron and electron-phonon interaction strengths

   https://doi.org/10.1038/s42005-020-00442-x  

   Wilson, Richard B.; Coh, Sinisa (December 2020, Communications Physics)

   null (Ed.)

   Abstract Understanding how photoexcited electron dynamics depend on electron-electron (e-e) and electron-phonon (e-p) interaction strengths is important for many fields, e.g. ultrafast magnetism, photocatalysis, plasmonics, and others. Here, we report simple expressions that capture the interplay of e-e and e-p interactions on electron distribution relaxation times. We observe a dependence of the dynamics on e-e and e-p interaction strengths that is universal to most metals and is also counterintuitive. While only e-p interactions reduce the total energy stored by excited electrons, the time for energy to leave the electronic subsystem also depends on e-e interaction strengths because e-e interactions increase the number of electrons emitting phonons. The effect of e-e interactions on energy-relaxation is largest in metals with strong e-p interactions. Finally, the time high energy electron states remain occupied depends only on the strength of e-e interactions, even if e-p scattering rates are much greater than e-e scattering rates. 

   more » « less
4. Electron-only reconnection and associated electron heating and acceleration in PHASMA

   https://doi.org/10.1063/5.0082633  

   Shi, Peiyun; Srivastav, Prabhakar; Barbhuiya, M. Hasan; Cassak, Paul A.; Scime, Earl E.; Swisdak, M.; Beatty, Cuyler; Gilbert, Tyler; John, Regis; Lazo, Matthew; et al (March 2022, Physics of Plasmas)

   Using incoherent Thomson scattering, electron heating and acceleration at the electron velocity distribution function (EVDF) level are investigated during electron-only reconnection in the PHAse Space MApping (PHASMA) facility. Reconnection arises during the merger of two kink-free flux ropes. Both push and pull type reconnection occur in a single discharge. Electron heating is localized around the separatrix, and the electron temperature increases continuously along the separatrix with distance from the X-line. The local measured gain in enthalpy flux is up to 70% of the incoming Poynting flux. Notably, non-Maxwellian EVDFs comprised of a warm bulk population and a cold beam are directly measured during the electron-only reconnection. The electron beam velocity is comparable to, and scales with, electron Alfvén speed, revealing the signature of electron acceleration caused by electron-only reconnection. The observation of oppositely directed electron beams on either side of the X-point provides “smoking-gun” evidence of the occurrence of electron-only reconnection in PHASMA. 2D particle-in-cell simulations agree well with the laboratory measurements. The measured conversion of Poynting flux into electron enthalpy is consistent with recent observations of electron-only reconnection in the magnetosheath [Phan et al., Nature 557, 202 (2018)] at similar dimensionless parameters as in the experiments. The laboratory measurements go beyond the magnetosheath observations by directly resolving the electron temperature gain. 

   more » « less
5. Evidence of a coupled electron-phonon liquid in NbGe2

   https://doi.org/10.1038/s41467-021-25547-x  

   Yang, Hung-Yu; Yao, Xiaohan; Plisson, Vincent; Mozaffari, Shirin; Scheifers, Jan P.; Savvidou, Aikaterini Flessa; Choi, Eun Sang; McCandless, Gregory T.; Padlewski, Mathieu F.; Putzke, Carsten; et al (September 2021, Nature Communications)

   Abstract Whereas electron-phonon scattering relaxes the electron’s momentum in metals, a perpetual exchange of momentum between phonons and electrons may conserve total momentum and lead to a coupled electron-phonon liquid. Such a phase of matter could be a platform for observing electron hydrodynamics. Here we present evidence of an electron-phonon liquid in the transition metal ditetrelide, NbGe₂, from three different experiments. First, quantum oscillations reveal an enhanced quasiparticle mass, which is unexpected in NbGe₂with weak electron-electron correlations, hence pointing at electron-phonon interactions. Second, resistivity measurements exhibit a discrepancy between the experimental data and standard Fermi liquid calculations. Third, Raman scattering shows anomalous temperature dependences of the phonon linewidths that fit an empirical model based on phonon-electron coupling. We discuss structural factors, such as chiral symmetry, short metallic bonds, and a low-symmetry coordination environment as potential design principles for materials with coupled electron-phonon liquid. 

   more » « less