Office of Research, UC Riverside
Vivek Aji
Associate Professor
Physics and Astronomy
vivekj@ucr.edu
(951) 827-7302


Novel Phenomena in spin orbit coupled systems

AWARD NUMBER
007718-005
FUND NUMBER
33194
STATUS
Active
AWARD TYPE
3-Grant
AWARD EXECUTION DATE
7/10/2017
BEGIN DATE
9/15/2015
END DATE
8/31/2018
AWARD AMOUNT
$2,000

Sponsor Information

SPONSOR AWARD NUMBER
1506707
SPONSOR
NATIONAL SCIENCE FOUNDATION
SPONSOR TYPE
Federal
FUNCTION
Organized Research
PROGRAM NAME

Proposal Information

PROPOSAL NUMBER
15040430
PROPOSAL TYPE
New
ACTIVITY TYPE
Basic Research

PI Information

PI
Aji, Vivek
PI TITLE
Other
PI DEPTARTMENT
Physics and Astronomy
PI COLLEGE/SCHOOL
College of Nat & Agr Sciences
CO PIs

Project Information

ABSTRACT

NONTECHNICAL SUMMARY

This award supports theoretical research and education to study new states of electronic matter with novel functionalities in many body systems. The PI will investigate states involving a large number of electrons in materials that arise from the interplay of two ingredients: 1) the interaction between pairs of electrons, and 2) strong spin-orbit interaction which quantifies the influence of an electron's spin, a fundamentally quantum mechanical phenomenon in which an electron appears to spin like a top, on its motion. Over the last decade a number of new phases of matter have been theoretically proposed and experimentally discovered. In many cases, their unique characteristics can be described with the help of concepts from the branch of mathematics dealing with shape, deformation and topology. The intersection of topology, spin-orbit coupling and many body physics is a rich and current area of study that may lead to new device technologies.

The PI will focus investigation on two specific kinds of materials systems. The first kind is comprised of the two-dimensional transition metal dichalcogenides. These are materials that are essentially a single atomic layer thick, made from a transition metal such as the elements Tungsten or Molybdenum, and a chalcogen such as the elements Sulphur or Selenium. The projects explore: i) how the coupling of spin and electron motion can lead to new magnetic properties with the potential for device applications; ii) what new magnetic states of matter are possible due to the interactions; and iii) whether consequences of topology allow for new ways of controlling device characteristics using circularly polarized light. The second kind is comprised of the topological semimetals, which are intermediate between a metal and a semiconductor. The PI will map out the possible phases and phenomena supported in these systems, and in parallel use the lessons learned to develop a better understanding of materials with strong spin-orbit interactions.

The research team will include one graduate student who will be trained in the needed technical expertise, and in developing an understanding of real materials. The award will help support an outreach effort at University of California-Riverside, by providing stipends for high school teachers to attend a week long Summer Academy for Teachers hosted by the Physics and Astronomy department.


TECHNICAL SUMMARY

This award supports theoretical research and education to study new states of electronic matter with novel functionalities in many body systems. The PI aims to discover and design new states of matter and associated properties arising from the interplay of spin-orbit coupling and interactions in many-body systems. Topologically nontrivial states such as topological insulators and Weyl semimetals arise in non-interacting systems. Natural questions that arise are: What happens when interactions are included? Do the topological aspects survive? Are new correlated phases realized which allow new functionalities? The PI will address these questions in the context of two-dimensional dichalcogenides and three-dimensional Weyl semimetals.

The projects on two dimensional dichalcogenides aim to characterize new magnetic phenomena that arise due to unique band structure afforded by spin-orbit coupling. For example the nature of the Kondo effect, where an impurity spin is screened by the host electrons, will be established. Opto-electronic coupling with spin specificity provides a new probe to test and manipulate this correlated phase which will be theoretically analyzed. Nontrivial topology also has potential application in spintronics due to the anomalous velocity acquired by the electrons in external electric fields. The PI will explore these new functionalities and the viability of a nonlocal spin-valve device, and whether these phenomena can be further enhanced in proximity to a magnetic insulator.

Weyl semimetals are topological yet possess no energy gap in the bulk. This is due to the topological protection of the band crossings and only interactions that couple nodes with opposite topological charge can open a gap. The PI will characterize the excitonic phases and their properties that arise due to electron-electron Coulomb repulsion. A combination of symmetry considerations, field theoretic techniques, and computation will be utilized to achieve the broad objectives of the program.

The research team will include one graduate student who will be trained in the needed technical expertise, and in developing an understanding of real materials. The award will help support an outreach effort at University of California-Riverside, by providing stipends for high school teachers to attend a week long Summer Academy for Teachers hosted by the Physics and Astronomy department.
(Abstract from NSF)