Atomic-scale strain manipulation of a charge density wave

A charge density wave (CDW) is one of the fundamental instabilities of the Fermi surface occurring in a wide range of quantum materials. In dimensions higher than one, where Fermi ...

Electric switching of magnetism in 2D

News and Views: Electric switching of magnetism in 2D Combined electrostatic gating and magnetic fields switch a 2D atomic crystal from an antiferromagnetic to a ferromagnetic state.

Controlling Magnetic and Optical Properties of a van der Waals Crystal

Magnetic van der Waals (vdW) materials are the centerpiece of atomically thin devices with spintronic and optoelectronic functions. Exploring new chemistry paths to tune their magnetic and optical properties enables ...

Customizable message area. Check the theme option page to configure this.

Posted by Kenneth Burch On July - 1 - 2018 Comments Off on Atomic-scale strain manipulation of a charge density wave

A charge density wave (CDW) is one of the fundamental instabilities of the Fermi surface occurring in a wide range of quantum materials. In dimensions higher than one, where Fermi surface nesting can play only a limited role, the selection of the particular wavevector and geometry of an emerging CDW should in principle be susceptible to controllable manipulation. In this work, we implement a simple method for straining materials compatible with low-temperature scanning tunneling microscopy/spectros- copy (STM/S), and use it to strain-engineer CDWs in 2H-NbSe2. Our STM/S measurements, combined with theory, reveal how small strain-induced changes in the electronic band  [ Read More ]

Posted by Kenneth Burch On June - 5 - 2018 Comments Off on Electric switching of magnetism in 2D

News and Views: Electric switching of magnetism in 2D Combined electrostatic gating and magnetic fields switch a 2D atomic crystal from an antiferromagnetic to a ferromagnetic state.

Posted by Kenneth Burch On May - 6 - 2018 Comments Off on Controlling Magnetic and Optical Properties of a van der Waals Crystal

Magnetic van der Waals (vdW) materials are the centerpiece of atomically thin devices with spintronic and optoelectronic functions. Exploring new chemistry paths to tune their magnetic and optical properties enables significant progress in fabricating heterostructures and ultracompact devices by mechanical exfoliation. The key parameter to sustain ferromagnetism in 2D is magnetic anisotropy—a tendency of spins to align in a certain crystallographic direction known as easy‐axis. In layered materials, two limits of easy‐axis are in‐plane (XY) and out‐of‐plane (Ising). Light polarization and the helicity of topological states can couple to magnetic anisotropy with promising photoluminescence or spin‐orbitronic functions. Here, a unique  [ Read More ]

Posted by Kenneth Burch On February - 12 - 2018 Comments Off on Possible structural transformation and enhanced magnetic fluctuations in exfoliated α-RuCl3

We present Raman spectroscopy experiments on exfoliated α-RuCl3, from tens of nm thick down to single layers. Besides unexpectedly finding this material to be air stable, in the thinnest layers we observe the appearance with decreasing temperature of a symmetry-forbidden mode in crossed polarization, along with an anomalous broadening of a mode at 164 cm−1 that is known to couple to a continuum of magnetic excitations. This may be due to an enhancement of magnetic fluctuations and evidence for a distorted honeycomb lattice in single- and bilayer samples. Journal of Physics and Chemistry of Solids 

Posted by Kenneth Burch On May - 6 - 2017 Comments Off on Andreev Reflection without Fermi Surface Alignment

We address the controversy over the proximity effect between topological materials and high-T csuperconductors. Junctions are produced between Bi2Sr2CaCu2O and materials with different Fermi surfaces (Bi2Te3 and graphite). Both cases reveal tunneling spectra that are consistent with Andreev reflection. This is confirmed by a magnetic field that shifts features via the Doppler effect. This is modeled with a single parameter that accounts for tunneling into a screening supercurrent. Thus the tunneling involves Cooper pairs crossing the heterostructure, showing that the Fermi surface mismatch does not hinder the ability to form transparent interfaces, which is accounted for by the extended Brillouin zone and different lattice  [ Read More ]