O.M. Stewart Colloquium Series presents: Dr. Saurabh Maiti

Tuesday, February 13, 2018 4:00pm

Physics Bldg. Library, Rm. 223A


physics bldg

MU Physics & Astronomy Department's O. M. Stewart Colloquium Series presents, "The Nature of Collective Phenomenon in Spin-orbit Coupled Fermions," Tuesday, February 13, 4:00 p.m.

Dr. Saurabh Maiti, University of Massachusetts, writes, "When a correlated system responds to an external perturbation in a collective manner, it can do so coherently by forming a collective mode. Such an excitation, being bosonic in nature, can be macroscopically populated, and hence dominate the signal from any probe that couples to it. In a magnetic system (or in a system with an external field), one type of collective excitation is a spin-wave which has been exceptionally useful by allowing accurate g-factor determination and forming the basis of the futuristic efficient technology: Spintronics/Magnonics. This has led researchers to search for new structures/materials to better control and propagate spin-waves.

In this talk, I add a new dimension to the above search by presenting a novel collective mode that can be found in an interacting, spin-orbit coupled 2D electron gas:  the chiral-spin wave (CSW). The spin-orbit interaction lends such a mode some peculiar properties with the most glaring one being: it exists in non-magnetic systems, but can be tuned by applying an external field. The CSW also exhibits a very characteristic polarization. I will present how, because of spin-orbit coupling, it couples unusually to optical probes and will demonstrate a couple of recent experiments (on a quantum well and a topological insulator) showing behavior consistent with that of a CSW.  I will also indicate other candidate solid state systems that can host CSWs."