Phys.org March 14, 2024 Direct observation of the relevant interplay of the electronic structure of a single defect with other microscopic elementary excitations on their intrinsic length, time and energy scales has not been achieved. Researchers in Germany directly resolved in space, time, and energy how a spin–orbit-split energy level of an isolated selenium vacancy in a moiré-distorted WSe2 monolayer evolved under the controlled excitation of lattice vibrations. By locally launching a phonon oscillation and taking ultrafast energy-resolved snapshots of the vacancy’s states faster than the vibration period, they directly measured the impact of electron–phonon coupling in an isolated single-atom […]
Tag Archives: Quantum materials
Materials research explores design rules and synthesis of quantum memory candidates
Phys.org March 11, 2024 Stoichiometric Eu3+ compounds have recently shown promise for building dense, optically addressable quantum memory as the cations’ long nuclear spin coherence times and shielded 4f electron optical transitions provide reliable memory platforms but finding rare linewidth behavior within a wide range of potential chemical spaces remains difficult. Researchers at the University of Illinois, Urbana─Champaign, have found density functional theory (DFT) procedures that reliably reproduce known phase diagrams and correctly predict two experimentally realized quantum memory candidates. They synthesized the double perovskite halide Cs2NaEuF6 which is an air-stable compound with a calculated band gap of 5.0 eV […]
Widely tunable terahertz lasers boost photo-induced superconductivity in K₃C₆₀
Phys.org October 12, 2023 Photoexcitation at terahertz and mid-infrared frequencies has emerged as an effective way to manipulate functionalities in quantum materials, in some cases creating non-equilibrium phases that have no equilibrium analogue. In K3C60, a metastable zero-resistance phase was observed that has optical properties, nonlinear electrical transport, and pressure dependencies compatible with non-equilibrium high-temperature superconductivity. An international team of researchers (Germany, Switzerland, Italy, UK) demonstrated a two-orders-of-magnitude increase in photo-susceptibility near 10 THz excitation frequency. At these drive frequencies, a metastable superconducting-like phase was observed up to room temperature. The discovery of a dominant frequency scale sheds light on the […]
Physicists coax superconductivity and more from quasicrystals
Phys.org September 28, 2023 Owing to their complexity and scarcity, quasicrystals are underexplored relative to periodic and amorphous structures. An international team of researchers (USA – MIT, Japan, Israel) introduced a new type of highly tunable quasicrystal easily assembled from periodic components. By twisting three layers of graphene with two different twist angles, they formed two mutually incommensurate moiré patterns. In contrast to many common atomic-scale quasicrystals, the quasiperiodicity in their system was defined on moiré length scales of several nanometres. This ‘moiré quasicrystal’ allowed them to tune the chemical potential and thus the electronic system between a periodic-like regime […]
Physicists discover first transformable nanoscale electronic devices
Phys.org April 17, 2023 Interfaces of van der Waals (vdW) materials, such as graphite and hexagonal boron nitride (hBN), exhibit low friction sliding due to their atomically flat surfaces and weak vdW bonding. An international team of researchers (UC Irvine, Japan) has demonstrated that microfabricated gold also slides with low friction on hBN. This enables the arbitrary post-fabrication repositioning of device features both at ambient conditions and in situ to a measurement cryostat. They demonstrated mechanically reconfigurable vdW devices where device geometry and position are continuously tunable parameters. By fabricating slidable top gates on a graphene-hBN device, they produced a […]
Breakthrough discovery in materials science challenges current understanding of photoemission
Phys.org March 14, 2023 Currently existing photocathodes are based on conventional metals and semiconductors that were discovered six decades ago with sound theoretical underpinnings. An international team of researchers (China, Japan, USA- Northeastern University) has observed unusual photoemission properties of a reconstructed surface of SrTiO3(100) single crystals. Unlike other positive-electron-affinity (PEA) photocathodes, their PEA SrTiO3 surface produced discrete secondary photoemission spectra at room temperature, characteristic of the efficient negative-electron-affinity photocathode materials. Using several photon energies they were able to produce a very intense coherent secondary photoemission. According to the researchers the observed emergence of coherence in secondary photoemission points to […]
Magnetism fosters unusual electronic order in quantum material
Phys.org March 13, 2023 Various correlated electronic phases have been discovered in kagome lattice materials, including magnetism, charge density waves, nematicity and superconductivity. Recently, a charge density wave was discovered in the magnetic kagome FeGe, providing a platform for understanding the interplay between charge order and magnetism in kagome materials. An internationl team of researchers (USA – Rice University, UC Berkeley, University of Washington, University, SLAC National Acclerator Laboratory, Oak Ridge National Laboratory, Lawrence Berkeley Laboratory, Israel, China) observed all three electronic signatures of the kagome lattice in FeGe using angle-resolved photoemission spectroscopy. They showed that the presence of van […]
The quantum twisting microscope: A new lens on quantum materials
Science Daily February 23, 2023 An international team of researchers (Israel, Japan) developed and demonstrated conceptually, a new type of tool — the quantum twisting microscope (QTM) — that could create novel quantum materials while simultaneously gazing into the most fundamental quantum nature of their electrons. It is capable of performing local interference experiments at its tip. The QTM is based on a unique van der Waals tip, allowing the creation of pristine two-dimensional junctions, which provide a multitude of coherently interfering paths for an electron to tunnel into a sample. With the addition of a continuously scanned twist angle […]
New instrument measures supercurrent flow; data has applications in quantum computing
Phys.org December 5, 2022 To understand the inner workings of quantum computing and enable supercomputing a team of researchers in the US (Iowa State University, University of Alabama at Birmingham, University of Wisconsin-Madison, Madison, Florida State University, Ames National Laboratory) built a Cryogenic Magneto-Terahertz Scanning Near-field Optical Microscope (cm-SNOM). It comprises three main equipment: i) a 5 T split pair magnetic cryostat with a custom made insert for mounting SNOM inside; ii) an atomic force microscope (AFM) unit that accepts ultrafast THz excitation and iii) a MHz repetition rate, femtosecond laser amplifier for high-field THz pulse generation and sensitive detection. […]
Researcher is studying materials whose traits resemble those of the human brain
Phys.org August 3, 2022 An international team of researchers (USA – Purdue University, New York University, UC San Diego, University of Chicago, Argonne National Laboratory, Northwestern, UC Santa Barbara, NIST, UC Davis, Brookhaven National Laboratory, France) summarizes and reflects on efforts to find “quantum materials” that can mimic brain function. CMOS has been engineered to keep different information states well-separated. It is not very well-designed for doing things where there is a lot of randomness and fluctuations. The human brain, on the other hand, can easily handle such tricky tasks while consuming dramatically less energy than modern computers. According to […]