CENTER FOR QUANTUM MATERIALS AND CONDENSED MATTER PHYSICS SEMINARS

NEWS: The CQM Distinguished Lecture series has been established  in the Fall of 2015 to bring to Stony Brook University the renown experts in the physics of quantum matter.

The lectures in this series will attract a broad audience of physicists from SBU and BNL,
and SBU graduate students.

September – December 2019

Sep
27
Fri
Reza Farhadifar (Flatiron Institute)
Sep 27 @ 1:30 pm – 2:30 pm

host: Jin Wang

Oct
4
Fri
Sasha Abanov (Stony Brook)
Oct 4 @ 1:30 pm – 2:30 pm
Oct
11
Fri
Riley Hanus (Northwestern U and ORNL)
Oct 11 @ 1:30 pm – 2:30 pm

host: Phil

Oct
18
Fri
Mehdi Jadidi (Columbia)
Oct 18 @ 1:30 pm – 2:30 pm

Title:  Optical Control of Chiral Charge Pumping in a Topological Weyl Semimetal

host: Dima Kharzeev

Abstract: Solids with topologically robust electronic states exhibit unusual electronic and optical transport properties that do not exist in other materials. A particularly interesting example is chiral charge pumping, the so-called chiral anomaly, in recently discovered topological Weyl semimetals, where simultaneous application of parallel DC electric and magnetic fields creates an imbalance in the number of carriers of opposite topological charge (chirality). Here, using time-resolved terahertz measurements on the Weyl semimetal TaAs in a magnetic field, we optically interrogate the chiral anomaly by dynamically pumping the chiral charges and monitoring their subsequent relaxation. Theory based on Boltzmann transport shows that the observed effects originate from an optical nonlinearity in the chiral charge pumping process. Our measurements reveal that the chiral population relaxation time is much greater than 1 ns. The observation of terahertz-controlled chiral carriers with long coherence times and topological protection suggests the application of Weyl semimetals for quantum optoelectronic technology.
Oct
25
Fri
Laszlo Forro (EPFL, Lausanne)
Oct 25 @ 1:30 pm – 2:30 pm

host: Laszlo Mihaly

Nov
1
Fri
Vidvuds Ozolins (Yale)
Nov 1 @ 1:30 pm – 2:30 pm

host: Phil Allen

Nov
8
Fri
Anderson Janotti (University of Delaware)
Nov 8 @ 1:30 pm – 2:30 pm

Title: Emergent Phenomena at the Interface of Complex Oxides

Host: Cyrus Dreyer

Progress in epitaxial growth of complex oxides have led to heterostructures with exquisite physical phenomena, such as the formation of a high-density two-dimensional electron gas (2DEG) at the interface between two normally insulating materials—e.g. SrTiO3/LaAlO3. Superconductivity and magnetic ordering have been demonstrated in these systems, sparking the interest in novel device applications. The formation of a 2DEG at the interface between SrTiO3 and Mott insulators, such as GdTiO3, has also been demonstrated, with electron densities that are over an order of magnitude higher than those realized with conventional semiconductors. Charge transport in these systems exhibit intriguing behavior, varying drastically from metal to insulator depending on the thickness of the building-block layers. Intensive research efforts in the last decade have raised questions regarding the origin of the excess charge, the mechanisms that determine the density of the 2DEG, and fundamental properties of the 2DEG. In this presentation, we will discuss how computer simulations can provide insights into the origin and nature of the 2DEG. Based on results of first-principles calculations we will discuss electron correlation effects and how the electronic structure of these heterostructures can be drastically altered, turning from metallic into insulating, through charge localization in ultrathin layers. Finally, we will address the interplay between orbital, charge, and spin in the manipulation of the magnetic ordering observed in some of these heterostructures.

Nov
15
Fri
Peter W. Stephens (SBU P&A)
Nov 15 @ 1:30 pm – 2:30 pm

title: Manganese Cyanide Tinkertoys

Dec
6
Fri
Justin Wilson (Rutgers)
Dec 6 @ 1:30 pm – 2:30 pm

Host: Jen Cano