Phasonic degrees of freedom are unique to quasiperiodic structures and play a central role in poorly understood properties of quasicrystals from excitation spectra to wave function statistics to electronic transport. However, phasons are challenging to access dynamically in the solid state due to their complex long-range character and the effects of disorder and strain. We report phasonic spectroscopy of a quantum gas in a one-dimensional quasicrystalline optical lattice. We observe that strong phasonic driving produces a nonperturbative high-harmonic plateau strikingly different from the effects of standard dipolar driving. Tuning the potential from crystalline to quasicrystalline, we identify spectroscopic signatures of quasiperiodicity and interactions and map the emergence of a multifractal energy spectrum, opening a path to direct imaging of the Hofstadter butterfly.
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http://dx.doi.org/10.1103/PhysRevLett.123.223201 | DOI Listing |
ACS Nano
July 2024
The Molecular Foundry, Lawrence Berkeley National Laboratory, Berkeley, California 94720, United States.
Stacking van der Waals crystals allows for the on-demand creation of a periodic potential landscape to tailor the transport of quasiparticle excitations. We investigate the diffusion of photoexcited electron-hole pairs, or excitons, at the interface of WS/WSe van der Waals heterostructure over a wide range of temperatures. We observe the appearance of distinct interlayer excitons for parallel and antiparallel stacking and track their diffusion through spatially and temporally resolved photoluminescence spectroscopy from 30 to 250 K.
View Article and Find Full Text PDFNat Mater
April 2023
Department of Physics, University of Illinois at Urbana-Champaign, Urbana, IL, USA.
The lowest-lying fundamental excitation of an incommensurate charge-density-wave material is believed to be a massless phason-a collective modulation of the phase of the charge-density-wave order parameter. However, long-range Coulomb interactions should push the phason energy up to the plasma energy of the charge-density-wave condensate, resulting in a massive phason and fully gapped spectrum. Using time-domain terahertz emission spectroscopy, we investigate this issue in (TaSe)I, a quasi-one-dimensional charge-density-wave insulator.
View Article and Find Full Text PDFJ Phys Condens Matter
June 2020
Indian Institute of Science Education and Research Thiruvananthapuram (IISER-TVM), Maruthamala P.O. Vithura, Kerala 695551, India.
We provide spectroscopic evidence for the charge density wave (CDW) phason mode at ≈0.93 THz in the two-leg, spin-1/2 ladders of SrCuO using terahertz time-domain spectroscopy. We find that annealing in an oxygen atmosphere or doping with a low concentration of Co (≾1%) does not affect the CDW phason mode.
View Article and Find Full Text PDFPhys Rev Lett
November 2019
Department of Physics, University of California, Santa Barbara, California 93106, USA.
Phasonic degrees of freedom are unique to quasiperiodic structures and play a central role in poorly understood properties of quasicrystals from excitation spectra to wave function statistics to electronic transport. However, phasons are challenging to access dynamically in the solid state due to their complex long-range character and the effects of disorder and strain. We report phasonic spectroscopy of a quantum gas in a one-dimensional quasicrystalline optical lattice.
View Article and Find Full Text PDFNat Commun
May 2017
Peter Grünberg Institut (PGI-7) and JARA-FIT, Forschungszentrum Jülich GmbH, 52425 Jülich, Germany.
Since their discovery, quasicrystals have attracted continuous research interest due to their unique structural and physical properties. Recently, it was demonstrated that dodecagonal quasicrystals could be used as bandgap materials in next-generation photonic devices. However, a full understanding of the formation mechanism of quasicrystals is necessary to control their physical properties.
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