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.

October 2012 – October 2013

Oct
12
Fri
Dr Alessandro Cunsolo, Brookhaven National Laboratory
Oct 12 @ 9:30 am – 10:30 am

The Intriguing Dynamic Behavior of Water Unveiled by High-Frequency Inelastic Spectroscopies

Nearly two decades of Inelastic X Ray and Neutron Scattering investigations on water will be reviewed. They evidenced an extremely reach phenomenology, which was in the focus of a lively debate: from the so called “fast sound” phenomenon, revealing the presence of a structural relaxation, to the anomalous pressure behavior of microscopic diffusion and the onset of shear waves in the spectrum. It will be shown that these effects are intimately related to the existence of a hydrogen bond network. Finally, the new scenarios opened up by the development of next-generation spectrometers will be briefly outlined.

Nov
9
Fri
From turbine engines to hip implants: Designing multifunctional ceramic coatings. Speaker: Molly M. Gentleman, SBU Mat. Sci.
Nov 9 @ 8:30 am – 9:30 am

The use of ceramic coatings for thermal and environmental protection in high temperature turbine applications has become the industry standard over the past several decades. As a result, the drive to improve the efficiency of these systems through the development of sensors, improved chemical stability and mechanical behavior, and development of other functional properties has lead to an ever increasing range of applications where ceramic coatings can be beneficial. In this talk, the modification and control of the physical properties of the constituent ceramics in conjunction with deposition processes will be described as the basis for the expansion of the uses of thermal sprayed ceramic coatings to include superhydrophobic, antifouling, and biological applications.  Specifically, work on the development of ferroelastically toughened ceramics, and low surface energy ceramics will be discussed.  Examples will be given of the development of new high toughness thermal barrier coatings, erosion-reducing coatings for steam turbines, and improved cell growth rates for biological implants.

Dr. Gentleman received a BS in Metallurgical and Materials Engineering from Illinois Institute of Technology in Chicago in 2001.  Following that she received her PhD in Materials from the University of California, Santa Barbara in 2006.  She then went on to take a position as a materials scientist at GE Global Research Center in Niskayuna, NY where she worked as a member of the Coatings and Surface Technology Laboratory and the Nanotechnology Advanced Technology program.  Her work at GE resulted in twelve currently issued patents as lead inventor and thirteen pending patent applications on wetting resistant materials and environmental barrier coatings.  She was an assistant professor in the Mechanical Engineering Department of Texas A&M from 2010-2012 and serves as a visiting fellow at NIST in the Center for Nanaoscale Science and Technology.  Dr. Gentleman joined the Materials Scinece and Engineering Department of Stony Brook University this year.

Mar
1
Fri
Roxana Margine, SUNY Binghamton: Development of advanced computational methods for description of superconductors.
Mar 1 @ 1:30 pm – 2:30 pm

Prediction of key superconducting properties such as the critical temperature and the superconducting energy gap remains one of the outstanding challenges in modern electronic structure theory. Up till now, estimation of the critical temperature in conventional superconductors has been done primarily with the semiempirical McMillan’s approach [1]. This approximation relies on the averaged-out strength of the electron-phonon coupling making it unsuitable for studying emerging classes of layered and low-dimensional superconductors.
I have recently developed a computational method that combines the anisotropic Migdal-Eliashberg formalism [2] with electron-phonon interpolation based on maximally-localized Wannier functions [3] allowing a proper treatment of the anisotropic effects at a remarkably low computational cost [4]. In this talk I will overview the theoretical background and performance of the method for two prototypical superconductors, Pb and MgB2. The developed computational tool has been implemented in EPW and will be released as an open-source code within the QUANTUM ESPRESSO package [5].
[1] W. L. McMillan, Phys. Rev. 167, 331 (1968).
[2] P. A. Allen and B. MitrovÍc, Solid State Phys. 37, 1 (1982).
[3] N. Marzari, A. A. Mostofi, J. R. Yates, I. Souza, D. Vanderbilt, Rev. Mod. Phys. 84, 1419 (2012)
[4] E. R. Margine and F. Giustino, Phys. Rev. B 87, 024505 (2013).
[5] http://epw.org.uk/; http://www.quantum-espresso.org

Apr
12
Fri
Andreas Ruediger (INRS, Quebec): Tip-enhanced Raman spectroscopy – breaking the diffraction limit towards the nanoworld
Apr 12 @ 1:30 pm – 2:45 pm

Andreas Ruediger
Nanoelectronics-Nanophotonics
Institut National de la Recherche Scientifique – Énergie, Matériaux et Télécommunications, Université du Québec
1650 Boulevard Lionel-Boulet, J3X1S2 Varennes, Québec, Canada
ruediger@emt.inrs.ca

Optical spectroscopy is among the most versatile tools in physics, chemistry, material and life science covering a large spectral range and therefore a variety of light-matter interactions, both linear and non-linear. But regardless of whether the technique is absorption, fluorescence, elastic and inelastic scattering, second harmonic generation only to mention a few and regardless of the use of lasers for scanning techniques: the diffraction limit as quantified in the 19th century remains a limitation for the spatial resolution to the order of the excitation wavelength. This corresponds to several hundred nanometers for visible light and used to be a roadblock for the application in nanoscience. Complementary nano-characterization techniques including electron microscopy and scanning probe microscopy pushed the resolution limit to the atomic level, however at the price of severe limitations to the chemical and structural information as compared to optical techniques.
In very recent years, the combination of scanning probe techniques such as scanning tunneling and atomic force microscopy (STM and AFM respectively) with confocal laser scanning microscopy has pushed the limits of optical spectroscopy to new horizons. The concept relies on the use of a scanning probe tip to act as a local near-field amplifier (‘nano-antenna’) in the focus of a confocal laser-scanning microscope. The enhancement and confinement of the electromagnetic field is typically achieved through the resonant excitation of surface plasmons in noble-metal tips.
The proof of concept for this technique was delivered about a decade ago [1] and provided evidence for single-molecule sensitivity in resonant-Raman spectroscopy. With dedicated experimental setups, tip-enhanced Raman spectroscopy has achieved spatial resolution of 10 nm and less while preserving most of the spectral information of conventional Raman spectroscopy. The experimental key challenge remains in the reproducible fabrication of resonating tips and their mid-term stability.
This presentation will briefly revisit some merits of conventional spectroscopy in physics and material science before introducing the basics of tip-enhanced spectroscopy. We report on a tip-enhanced Raman experiment for non-transparent, isolating samples as frequently encountered in oxide nanoelectronics, one of the research focuses of our team. We achieved a spatial resolution of 14 nm FWHM on carbon nanotubes [2]. Our latest results on lead titanate (PbTiO3) nanoislands grown by a template approach show that we achieve tip-enhanced Rayleigh and Raman scattering, the latter with an unprecedented spatial resolution of about 6 nm. Tip-enhanced optical spectroscopy thus clearly is a promising contender for future generations of surface characterization techniques and the new limits for optical resolution are yet to be determined.

[1] B. Pettinger, B. Ren, G. Picardi, R. Schuster, G. Ertl, ‘Nanoscale Probing of Adsorbed Species by tip-enhanced Raman spectroscopy’, Physical Review Letters, 92 (2004) 096101
[2] M. Nicklaus, C. Nauenheim, A. Krayev, V. Gavrilyuk, A. Belyaev, A. Ruediger, ‘Tip-enhanced Raman spectroscopy with objective scanner on opaque samples’, Review of Scientific Instruments, 83 (2012) 066102

Apr
26
Fri
Seamus Davis, Cornell and BNL: Visualizing Creation, Destruction and Pairing of Heavy Fermions @ B-131, Physics
Apr 26 @ 1:30 pm – 2:30 pm

Visualizing Creation, Destruction and Pairing of Heavy Fermions

J. C. Séamus Davis

Cornell University & Brookhaven National Laboratory

 

We recently introduced spectroscopic imaging scanning tunnelling microscopy (SI-STM) – a technique for simultaneously imaging electronic structure in real-space (r-space) and momentum-space (k-space) – to the study of ‘heavy fermion’ materials. SI-STM is particularly powerful approach in this case because the genesis of heavy fermions is hybridization between electrons localized in r-space and those delocalized in k-space. Using SI-STM, we achieved the first observation of splitting of a light k-space band into two new heavy fermion bands due to the r-space hybridization process (Nature 465, 570 (2010) i.e. visualization of the creation of heavy fermions. More recently we imaged the electronic structure of a Kondo-hole – a spinless atom substituted for magnetic atom in the heavy fermion compound. By introducing another new approach, the ‘hybridization gapmap’, to heavy fermion studies, we discovered intense nanoscale heterogeneity of hybridization due to Kondo-hole doping (PNAS 108, 18233 (2011)). Finally, I will discuss the exciting prospects for visualising Cooper pairing of heavy fermions and thus for identifying the mechanism of heavy fermion superconductivity. A very rapid uptake of these SI-STM approaches to visualizing electronic structure of heavy fermions is now occurring across this research community.

May
10
Fri
SEMINAR CANCELLED
May 10 @ 1:30 pm – 2:30 pm

CANCELLED TALK

Aug
23
Fri
V. Perebeinos (IBM): Carbon based electronics and photonics @ C-133
Aug 23 @ 1:30 pm – 2:45 pm

Joint Nuclear/CM seminar at 1 pm in C-133

Graphene and carbon nanotubes have remarkable electronic and optical properties.
There is strong interest in taking advantage of these properties in technology. In this
talk, I will first address the physics of the excited states dynamics, including radiative
and non-radiative decays in carbon nanotubes. Then I will review some of the intrinsic
transport properties of graphene and how they are affected by environmental interactions,
including substrate surface polar phonons, surface steps and changes in layer thickness
in epitaxial graphene films on SiC, graphene wrinkles in CVD graphene, metal-graphene
junctions and quantum interference effects, lateral transport in misoriented bilayer
graphene, and their possible impacts on electronics based on other two-dimensional
materials.

Sep
3
Tue
Prof. Michele Modugno, University of the Basque Country, Bilbao (Spain). Tight binding models for ultracold atoms in optical lattices @ AMO seminar room
Sep 3 @ 11:00 am – 12:00 pm

I will discuss how to construct tight-binding models for ultracold atoms in optical lattices, by means of the maximally localized Wannier functions for composite bands. Specific examples will be given for the case graphene-like potentials with two degenerate minima per unit cell, where a tight-binding model with up to third-nearest neighbors is capable to reproduce the structure of the Dirac points in a range of typical experimental parameters (see the recent experiment by Tarruell et al., Nature 483, 302 (2012)). I will also briefly review other recent theoretical results, including anomalous Bloch oscillations, shortcuts to adiabaticity, and quantum backflow.

Sep
6
Fri
Dmitri Kharzeev, Stony Brook University. Title: Presentation of the Center for Quantum Matterials at Stony Brook University @ B-131 Physics
Sep 6 @ 1:30 pm – 2:30 pm

The Center for Quantum Materials (CQM) is the new multi-institutional, inter-disciplinary research center that includes Stony Brook University, MIT, University of Manchester, University of Chicago, University of Massachusetts, University of Illinois, UC San Diego, and 6 leading Russian institutes. The Center is funded by the Skolkovo Institute of Science and Technology that is being created in Moscow with the help of MIT.

Stony Brook University is the leading institution of the international part of the Center. CQM combines the efforts of over 30 world’s leading scientists (including the Nobel prize winners Andre Geim and Frank Wilczek) and engineers, including the director of MIT Center for Electronic Materials Lionel Kimerling, director of MIT Center for Graphene Devices Tomas Palacios, associate director of MIT Research Laboratory of Electronics Marc Baldo, director of MIT Microsystems Technology Laboratory Vladimir Bulovic, and others.

As the leader of this large-scale international enterprise, Stony Brook University has founded the Stony Brook Center for Quantum Materials that will promote the cross-disciplinary collaboration at SBU, support a vigorous seminar, workshop and visitor program, and educate graduate students in this important field.

The goal of this talk will be to describe the program of the Center and to initiate an open discussion on how to use it to catalyze the cross-disciplinary interactions among the Stony Brook research groups working in the broad field of quantum materials.

Oct
4
Fri
Xu Du (Stony Brook University): Graphene hybrid devices
Oct 4 @ 1:30 pm – 2:30 pm

I will give a brief review on our recent works on graphene hybrid devices, including graphene-superconductor junctions and graphene-ferroelectric field effect transistors. Through fabrication of suspended graphene-NbN weak links, we were able to achieve the highest mobility in graphene Josephson devices. This allows study of the intrinsic superconducting proximity effect in a Dirac fermion system. Another type of device, a graphene-superconductor tunnel junction, have been studied as an sensitive bolometer, utilizing graphene’s ultra-small heat capacity, low resistivity and low electron thermal condutance . We characterize the bolometric response in these devices which allows us to study electron-phonon scattering at low temperatures. In the graphene-ferroelectric devices, we study the interplay between ferroelectric switching and charge trapping in graphene-STO/PTO superlattice field effect transistors. This provides a deeper understanding of the charge transfer and the impact of various charge trapping sources (including surface absorbates and oxygen deficiency) at the graphene-ferroelectric interface.