Welcome to the UC Berkeley Atomic, Nanoscale,
and Quantum Characterization Facility (ANQCF)
Research activities ongoing at the ANQCF cover five major focus areas, delineated below (ANQCF faculty investigator names are marked in bold):
1. Carbon Nanostructures (Crommie, Siddiqi, Shen, Wang, Zettl)
Carbon nanostructures comprised of covalently bonded carbon atoms display an amazing variety of geometries (such as buckyballs, nanotubes, and graphene sheets) with an equally amazing variety of physical properties. Fundamental questions being asked by ANQCF researchers in this area include the following: What limits electron mobility, mechanical strength, and thermal conductivity in graphitic carbon nanostructures? How do electrons, phonons, and photons couple within these structures, and how do they manifest differently in structures of differing dimensions? To what degree can the tunable nature of these nanostructures be exploited to create new nanodevices that are faster, more sensitive, and more energy efficient than current technology?
These questions are being addressed by several ANQCF investigators. The Zettl group has pioneered the study of carbon nanostructures and their use in a wide variety of prototypical “nanomachine” devices. Crommie has studied the molecular charging effects in doped C60 while Wang has focused optical probes onto individual carbon nanotubes to discover novel excitonic behavior. Graphene is being investigated collaboratively by Zettl, who has discovered novel graphene behavior in transmission electron microscopy (TEM) studies, by Crommie, who has used scanning tunneling microscopy (STM) to image defect states in graphene and to perform spectroscopy on back-gated graphene sheets, and by Wang, who has coupled electronic, optical, and mechanical excitations in graphene-based multilayers. New applications of graphene in superconducting devices are being investigated by Siddiqi and Zettl.
2. Quantum Fluids (Stamper-Kurn, Packard)
Quantum fluids, which include superfluid 4He and 3He and also gaseous BEC’s and degenerate Fermi gases, have unusual properties that push the boundaries of our under¬stan¬ding of matter. Fundamental questions being asked by ANQCF researchers in this area include the following: How do macroscopic quantum phenomena arise under differing interparticle inter¬actions? Do stable, equilibrated supersolids exist? Can the quantum coherence of such fluids enable new precise and ultra-sensitive detectors?
Current ANQCF projects aimed at answering these questions include explorations of mag¬netic order in dipolar atomic gases and of spontaneous symmetry breaking in magnetic superfluids (Stamper-Kurn). In the area of superfluid helium, ANQCF researchers are investigating 4He and 3He weak links, phase slip gyroscopes, and superfluid quantum inter¬ference devices (Packard).
3. Nanomagnetism (Qiu, Hellman, Crommie, Siddiqi)
Nanomagnetism is the study of spin behavior in confined geometries and small length scales. Quantum spin systems include magnetic molecules, thin films, and magnetic atoms trapped at a surface. Fundamental questions being asked by ANQCF researchers in this area include the following: What spin correlations arise due to varying spin-spin interactions in nanoscale magnetic systems? How do nanoscale magnets behave on surfaces? Can the microscopic and emergent properties of nanomagnetic structures be controlled, detected at the single-spin level, and used for spintronic devices?
Activities by ANQCF researchers addressing these questions include explorations of striped mag¬netic phases and magnetic quantum-well states in ultra-thin metal films (Qiu), of giant magnetoresistance and interface effects in magnetic multilayers (Hellman), of magnetic phase transitions in ultra-thin doped magnetic oxide films (Hellman), and of spin dynamics in single magnetic molecules (Siddiqi). Spin-polarized STM of atomic-scale mag¬netism on surfaces is also being developed to study spin-spin exchange coupling in atomically fabricated spin complexes (Crommie).
4. Quantum Information and Quantum-Based Precision Measurement (Clarke, Siddiqi, Häffner, Müller, Stamper-Kurn)
Researchers at the ANQCF and elsewhere have made enormous progress in controlling and measuring the phase-coherent properties of complex quantum systems, allowing for deep investigations into quantum phenomena and the development of quantum technologies for information processing and precision measurement. ANQCF researchers are investigating fundamental questions in this area such as the following: What are the fundamental mechanisms by which the environment strips a quantum state of its coherence? How do coupled quantum systems make the transition from quantum to classical behavior? Can large-scale atomic or solid-state quantum systems be engineered so as to protect quantum entanglement and make quantum computation and other advanced quantum technologies possible? Can long-lived quantum coherences and refined quantum-state manipulation techniques be exploited to measure fundamental physical parameters with unprecedented precision?
Current ANQCF projects addressing these issues involve the development of low-noise, non-dissipative Josephson junction-based amplifiers capable of quantum-limited measurement with high gain (Siddiqi), and of noise-resistant symmetric networks of superconducting qubits (Clarke, Siddiqi). In atomic physics, ANQCF researchers are studying quantum entanglement and state engineering of collective states of atomic motion using chip-based atom traps and optical resonators (Stamper-Kurn), and a new form of quantum electronics based on trapped ions interfaced with solid-state systems (Häffner).
5. Biophysical Nanomachines (Bustamante, Liphardt, Yildiz)
Currently the most sophisticated nanotechnology occurs naturally in biological organisms. Cells have evolved complex molecular devices that behave as nanomachines and that operate with clockwork precision. Fundamental questions remain regarding the mechanisms by which these biomotors operate, e.g. how is chemical energy from ATP molecules converted into mechanical force and how does the structure of such biomotors yield such well-regulated means to transport molecular cargo within cells? Can biomotors be combined with artificial structures to create higher-performance nanomachines?
Current ANQCF investigations into these questions include the development of powerful optical methods, based on observing plasmon resonances of interacting metallic nanoparticles (Liphardt) and on high-efficiency detection of single-molecule fluorescence (Yildiz), to resolve spatially the dynamical functions of biological nanomachines; and also single-molecule investigation of how viruses mechanically pack DNA strands into different microscopic configurations (Bustamante).