Riddle of the Kondo effect solved with an artificial atom and a 1D wire

A team of physicists at the University of Cologne has solved a long-standing problem of condensed matter physics: they have directly observed the Kondo effect (the re-grouping of electrons in a metal caused by magnetic impurities) visible in a single artificial atom. This has not been done successfully in the past, since the magnetic orbitals of atoms usually cannot be directly observed with most measurement techniques. However, the international research team led by Dr. Wouter Jolie at the University of Cologne's Institute for Experimental Physics used a new technique to observe the Kondo effect in an artificial orbital inside a one-dimensional wire floating above a metallic sheet of graphene. They report their discovery in the article "Modulated Kondo screening along magnetic mirror twin boundaries in monolayer MoS2" published in Nature Physics. When electrons moving through a metal encounter a magnetic atom, they are affected by the atom's spin—the magnetic pole of elementary particles. In trying to screen the effect of the atomic spin, the electron sea groups together close to the atom, forming a new many-body state which is called the Kondo resonance.

Semiconductor lattice marries electrons and magnetic moments

A model system created by stacking a pair of monolayer semiconductors is giving physicists a simpler way to study confounding quantum behavior, from heavy fermions to exotic quantum phase transitions.

The group's paper, "Gate-Tunable Heavy Fermions in a Moiré Kondo Lattice," published March 15 in Nature. The lead author is postdoctoral fellow Wenjin Zhao in the Kavli Institute at Cornell.

The project was led by Kin Fai Mak, professor of physics in the College of Arts and Sciences, and Jie Shan, professor of applied and engineering physics in Cornell Engineering and in A&S, the paper's co-senior authors. Both researchers are members of the Kavli Institute; they came to Cornell through the provost's Nanoscale Science and Microsystems Engineering (NEXT Nano) initiative.

The team set out to address what is known as the Kondo effect, named after Japanese theoretical physicist Jun Kondo. About six decades ago, experimental physicists discovered that by taking a metal and substituting even a small number of atoms with magnetic impurities, they could scatter the material's conduction electrons and radically alter its resistivity.

U.S. and European physicists have demonstrated a new method for predicting whether metallic compounds are likely to host topological states that arise from strong electron interactions.

Physicists from Rice University, leading the research and collaborating with physicists from Stony Brook University, Austria's Vienna University of Technology (TU Wien), Los Alamos National Laboratory, Spain's Donostia International Physics Center and Germany's Max Planck Institute for Chemical Physics of Solids, unveiled their new design principle in a study published online today in Nature Physics.

The team includes scientists at Rice, TU Wien and Los Alamos who discovered the first strongly correlated topological semimetal in 2017. That system and others the new design principle seeks to identify are broadly sought by the quantum computing industry because topological states have immutable features that cannot be erased or lost to quantum decoherence.

"The landscape of strongly correlated topological matter is both large and largely uninvestigated," said study co-author Qimiao Si, Rice's Harry C. and Olga K. Wiess Professor of Physics and Astronomy. "We expect this work will help guide its exploration."

Kondo physics in antiferromagnetic Weyl semimetal films

Emerging quantum materials can be defined by topology and strong electron correlations, although their applications in experimental systems are relatively limited. Weyl semimetals incorporating magnetism offer a unique and fertile platform to explore emerging phenomena in developing topological matter and topological spintronics. The triangular antiferromagnet Mn3Sn exhibits many exotic physical properties as an antiferromagnetic (AFM) Weyl semimetal (WSM), including an attractively large spontaneous Hall effect.

The spontaneous Hall effect was discovered more than a century ago and understood in terms of time-reversal symmetry breaking by the internal spin structure of antiferromagnetic, ferromagnetic or skyrmionic (small swirling topological defects in the magnetization) forms.

In a new report now published on Science Advances, Durga Khadka and a team of scientists in physics, materials science, neutron research and engineering in the U.S. reported the synthesis of epitaxial Mn3+xSn1−x films with compositions similar to bulk samples. When they replaced the tin (Sn) atoms with magnetic manganese (Mn) atoms in the samples, they noted the Kondo effect; a celebrated example of strong correlations to emerge, then develop coherence and induce a hybridization energy gap. The process of magnetic doping and gap opening facilitated rich extraordinary properties for the new materials.

It's time to get your Spring Clean on. You know, that whole “Flip in Fall, spin in Spring” mattress technique that Mom taught you? Well, it's that time of year ...

[vc_row][vc_column][vc_column_text]It’s time to get your Spring Clean on. You know, that whole “Flip in Fall, spin in Spring” mattress technique that Mom taught you? Well, it’s that time of year for the annual Spring clean and declutter followed by the much anticipated neighborhood yard sale. Much of the art of decluttering your mind stems from decluttering your space – your sanctuary à la casa.…