A5088472564- Quantum and electron transport phenomena
- Terahertz technology and applications
- Physics of Superconductivity and Magnetism
- Semiconductor Quantum Structures and Devices
- Perovskite Materials and Applications
- Mechanical and Optical Resonators
- Topological Materials and Phenomena
- Quantum Information and Cryptography
- Photonic and Optical Devices
- Surface and Thin Film Phenomena
- Near-Field Optical Microscopy
- Superconducting and THz Device Technology
- Quantum optics and atomic interactions
- Plasmonic and Surface Plasmon Research
- Gyrotron and Vacuum Electronics Research
- Atomic and Subatomic Physics Research
- Molecular Junctions and Nanostructures
- Quantum, superfluid, helium dynamics
- Chalcogenide Semiconductor Thin Films
- Quantum Mechanics and Non-Hermitian Physics
- Quantum Dots Synthesis And Properties
- Advanced Semiconductor Detectors and Materials
- Photorefractive and Nonlinear Optics
- Electronic and Structural Properties of Oxides
- 2D Materials and Applications
Iowa State University
2019-2025
Ames National Laboratory
2019-2025
Government of the United States of America
2024
United States Department of Energy
2020
Seoul National University
2018
We report terahertz (THz) light-induced second harmonic generation, in superconductors with inversion symmetry that forbid even-order nonlinearities. The THz emission vanishes above the superconductor critical temperature and arises from precession of twisted Anderson pseudospins at a multicycle, driving frequency is not allowed by equilibrium symmetry. explain microscopic physics dynamical breaking principle sub-THz-cycle using quantum kinetic modeling interplay between strong THz-lightwave...
Abstract The Higgs mechanism, i.e., spontaneous symmetry breaking of the quantum vacuum, is a cross-disciplinary principle, universal for understanding dark energy, antimatter and materials, from superconductivity to magnetism. Unlike one-band superconductors (SCs), conceptually distinct amplitude mode can arise in multi-band, unconventional via strong interband Coulomb interaction, but yet be accessed. Here we discover such hybrid demonstrate its control by light iron-based high-temperature...
Abstract The demand for disorder-tolerant quantum logic and spin electronics can be met by generating controlling dissipationless currents protected topology. Dirac fermions with helical spin-locking surface transport offer a way of achieving such goal. Yet, surface-bulk coupling lead to strong electron scattering bulk carriers phonons as well impurities, assisted dissipative channel, which results in “topological breakdown”. Here, we demonstrate that coherent lattice vibrations periodically...
We have developed a versatile near-field microscopy platform that can operate at high magnetic fields and below liquid-helium temperatures. use this to demonstrate an extreme terahertz (THz) nanoscope operation obtain the first cryogenic magneto-THz time-domain nano-spectroscopy/imaging temperatures as low 1.8 K, of up 5 T, with 0-2 THz. Our Cryogenic Magneto-Terahertz Scattering-type Scanning Near-field Optical Microscope (or cm-THz-sSNOM) instrument is comprised three main equipment: (i) T...
A light-induced phase transition in a Dirac material offers insight into how these materials respond to periodic driving (that is, quantum back-and-forth motion), information necessary for topology-based computation and topological transistors.
We discover hidden Rashba fine structure in CH$_3$NH$_3$PbI$_3$ and demonstrate its quantum control by vibrational coherence through symmetry-selective vibronic (electron-phonon) coupling. Above a critical threshold of single-cycle terahertz pump field, Raman phonon mode distinctly modulates the middle excitonic states with {\em persistent} for more than ten times longer ones on two sides that predominately couple to infrared phonons. These beats, together first-principles modeling...
Emerging topological semimetals offer promise of realizing electronics enabled by terahertz (THz) current persistent against impurity scattering. Yet most fundamental issues remain on how to image nanoscale conductivity inhomogeneity. Here we show noninvasive and contactless mapping at THz-nm limit electronic heterogeneity nanostrip junctions in a Dirac material ZrTe5. A clear Fermion density transition, manifested as the exclusive THz contrast, is quantitatively analyzed profiled both sides...
We conducted a comprehensive study of the non-equilibrium dynamics Cooper pair breaking, quasiparticle (QP) generation, and relaxation in niobium (Nb) cut from superconducting radio-frequency (SRF) cavities, as well various Nb resonator films transmon qubits. Using ultrafast pump–probe spectroscopy, we were able to isolate coherence pair-breaking responses. Our results reveal both similarities notable differences temperature- magnetic-field-dependent SRF cavity thin-film samples. Moreover,...
Two-level atoms ultrastrongly coupled with single-mode cavity photons are predicted to exhibit a quantum phase transition, entering in which both the atomic polarization and photonic field finite even without external driving. However, this phenomenon, superradiant transition (SRPT), is forbidden by no-go theorem due existence of diamagnetic term. Here, we present spectroscopic evidence for magnonic SRPT ErFeO 3 , where role mode (two-level atoms) played an Fe 3+ magnon (Er spins). The...
Direct visualization and quantitative evaluation of charge filling in grain boundary (GB) traps hybrid metal halide perovskites require dynamic conductivity imaging simultaneously at the terahertz (THz) frequency nanometer (nm) spatial scales not accessible by conventional transport methods used thus far. Here, we apply a THz near-field nanoconductivity mapping to archetypal perovskite photovoltaic films demonstrate that it is powerful tool reveal distinct dielectric heterogeneity due...
Superconducting quantum circuits (SQC) are one of the most promising hardware platforms for computing, yet their performance is currently limited by presence various structural defects inside circuit's structure. Despite impressive progress in past decade, a precise understanding origin these from fabrication processes and impact on coherence still lacking. In this study, we performed comprehensive investigation microstructure, superconductivity, resonator quality factor Nb films deposited...
Tunneling is the most fundamental quantum mechanical phenomenon with wide-ranging applications. Matter waves such as electrons in solids can tunnel through a one-dimensional potential barrier, e.g. an insulating layer sandwiched between conductors. A general approach to control tunneling currents apply voltage across barrier. Here, we form closed loops of barriers exposed external optical manipulate ultrafast electrons. Eddy induced by incoming electromagnetic pulses project upon ring,...
We report the discovery of helicity-dependent ultrafast photocurrent generation in organic-inorganic perovskite by measuring terahertz (THz) electric field emissions time-domain. find signatures circular photogalvanic effect (CPGE) where right circularly polarized light and left lead to different generation. The direction is also resolved polarization emitted THz pulses. Furthermore, we observe distinct wavelength-dependent, coherent phonon dynamics using pump-induced differential...
The fundamental challenge underlying superconducting quantum computing is to characterize heterogeneity and disorder in the circuits. These nonuniform distributions often lead local electric field concentration, charge scattering, dissipation ultimately decoherence. It particularly challenging probe deep sub-wavelength distribution under electromagnetic wave coupling at individual nano-junctions correlate them with structural imperfections from interface boundary, ubiquitous Josephson...
Two-level atoms coupled with single-mode cavity photons are predicted to exhibit a quantum phase transition when the coupling strength exceeds critical value, entering in which atomic polarization and photonic field finite even at zero temperature without external driving. However, this phenomenon, superradiant (SRPT), is forbidden by no-go theorem due existence of diamagnetic term Hamiltonian. Here, we present spectroscopic evidence for magnonic SRPT ErFeO$_3$, where role mode (two-level...
Abstract The challenge underlying superconducting quantum computing is to remove materials bottleneck for highly coherent devices. nonuniformity and complex structural components in the circuits often lead local electric field concentration, charge scattering, dissipation ultimately decoherence. Here we visualize interface dipole heterogeneous distribution of individual Al/AlO x /Al junctions employed transmon qubits by broadband terahertz scanning near-field microscopy that enables...
<title>Abstract</title> Two-level atoms coupled with single-mode cavity photons are predicted to exhibit a quantum phase transition when the coupling strength exceeds critical value, entering in which atomic polarization and photonic field finite even at zero temperature without external driving. However, this phenomenon, superradiant (SRPT), is forbidden by no-go theorem due existence of diamagnetic term Hamiltonian. Here, we present spectroscopic evidence for magnonic SRPT...
One manifestation of light-Weyl fermion interaction is the emergence chiral magnetic effects under fields. Probing real space responses at terahertz (THz) scales challenging but highly desired, as local are less affected by topologically trivial inhomogeneity that ubiquitous in spatially averaged measurements. Here, we implement a cryogenic THz microscopy instrument field environment—a task only recently achieved. We explore technical approach this system and characterize field’s influence...
Superconducting quantum circuits (SQC) are one of the most promising hardware platforms for computing, yet their performance is currently limited by presence various structural defects inside circuit's structure. Despite impressive progress in past decade, a precise understanding origin these from fabrication processes and impact on coherence still lacking. In this study, we performed comprehensive investigation microstructure, superconductivity, resonator quality factor Nb films deposited...
We conducted a comprehensive study of the non-equilibrium dynamics Cooper pair breaking, quasiparticle (QP) generation, and relaxation in niobium (Nb) cut from superconducting radio-frequency cavities, as well various Nb resonator films transomon qubits. Using ultrafast pump-probe spectroscopy regime minimal condensate depletion, we were able to isolate coherence pair-breaking responses. Our results reveal both similarities notable differences temperature- magnetic field-dependent samples....
Abstract Probing the time evolution of terahertz electric field within subwavelength dimensions plays a crucial role in observing nanoscale lightwave interactions with fundamental excitations condensed-matter systems and artificial structures, such as metamaterials. Here, we propose novel probing method for measuring potentials across nanogaps using combination optical pulse excitations. To achieve this, employ ring-shaped that enclose metallic island, allowing us to capture tunneling...