18 research outputs found
Probing quantum spin liquids with a quantum twisting microscope
The experimental characterization of quantum spin liquids poses significant
challenges due to the absence of long-range magnetic order, even at absolute
zero temperature. The identification of these states of matter often relies on
the analysis of their excitations. In this paper, we propose a method for
detecting the signatures of the fractionalized excitations in quantum spin
liquids using a tunneling spectroscopy setup. Inspired by the recent
development of the quantum twisting microscope, we consider a planar tunneling
junction, in which a candidate quantum spin liquid material is placed between
two graphene layers. By tuning the relative twist angle and voltage bias
between the leads, we can extract the dynamical spin structure factor of the
tunneling barrier with momentum and energy resolution. Our proposal presents a
promising tool for experimentally characterizing quantum spin liquids in
two-dimensional materials.Comment: 18 pages, 3 figure
Collective Wigner crystal tunneling in carbon nanotubes
The collective tunneling of a a Wigner necklace - a crystalline state of a
small number of strongly interacting electrons confined to a suspended nanotube
and subject to a double well potential - is theoretically analyzed and compared
with experiments in [Shapir , Science , 870
(2019)]. Density Matrix Renormalization Group computations, exact
diagonalization, and instanton theory provide a consistent description of this
very strongly interacting system, and show good agreement with experiments.
Experimentally extracted and theoretically computed tunneling amplitudes
exhibit a scaling collapse. Collective quantum fluctuations renormalize the
tunneling, and substantially enhance it as the number of electrons increases.Comment: 10 pages, 9 figure
The Quantum Twisting Microscope
The invention of scanning probe microscopy has revolutionized the way
electronic phenomena are visualized. While present-day probes can access a
variety of electronic properties at a single location in space, a scanning
microscope that can directly probe the quantum mechanical existence of an
electron at multiple locations would provide direct access to key quantum
properties of electronic systems, so far unreachable. Here, we demonstrate a
conceptually new type of scanning probe microscope - the Quantum Twisting
Microscope (QTM) - 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 2D 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 between the tip and sample, this microscope
probes electrons in momentum space similar to the way a scanning tunneling
microscope probes electrons in real space. Through a series of experiments, we
demonstrate room temperature quantum coherence at the tip, study the twist
angle evolution of twisted bilayer graphene, directly image the energy bands of
monolayer and twisted bilayer graphene, and finally, apply large local
pressures while visualizing the evolution of the flat energy bands of the
latter. The QTM opens the way for novel classes of experiments on quantum
materials