Day 3 :
Keynote Forum
Ivan Božović
Brookhaven National Laboratory, USA
Keynote: On the road to room-temperature superconductivity?
Biography:
Ivan Bozovic received his PhD in Solid State Physics from Belgrade University, Yugoslavia, where he was later elected a professor and the Physics Department Head. After moving to the USA in 1985 he worked at Stanford University, the Varian Research Center, and 1999-2002 in Oxxel, Bremen, Germany. Since 2003, he is the MBE Group Leader at Brookhaven National Laboratory, and since 2014 also an Adjunct Professor of Applied Physics at Yale University. He is a Member of European Academy of Sciences, Foreign Member of the Serbian Academy of Science and Arts, Fellow of APS, and Fellow of SPIE. He received the Bernd Matthias Prize for Superconducting Materials, SPIE Technology Award, the M. Jaric Prize, the BNL Science, and Technology Prize, was Max Planck and Van der Waals Lecturer and is a Gordon and Betty Moore Foundation PI. His research interests include basic physics of condensed states of matter, novel electronic phenomena including unconventional superconductivity, innovative methods of thin film synthesis and characterization, and nanoscale physics. He has published 11 research monographs and over 280 research papers, including 25 in Science and Nature journals.
Abstract:
Superconductivity in cuprates has many mysterious facets, but the most important question is why the critical temperature (Tc ) is so high. Our experiments target this question. We use atomic-layer-by-layer molecular beam epitaxy to synthesize atomically perfect thin films and multilayers of cuprates and other complex oxides. By atomic-layer engineering, we optimize the samples for a particular experiment. I will present the results of a focused and comprehensive study that took twelve years and over two thousand cuprate samples, perhaps without precedence in Condensed Matter Physics. We have measured the key physical parameters of the normal and superconducting states and established their precise dependence on doping, temperature, and external fields. This large data basis contains a wealth of information and constraints tightly the theory. One striking conclusion is that superconducting state cannot be described by the standard Bardeen-Cooper-Schrieffer theory, anywhere in the phase diagram. Next, the rotational symmetry of the electron fluid in the normal metallic state above Tc is always spontaneously broken-the so-called “electronic nematicity”-unlike in standard metals that behave like Fermi Liquids. Finally, the insulating state on the underdoped side is also unusual, with mobile charge clusters formed by localized pairs. All these features are quite exceptional, paint a new picture of high-Tc superconductivity in cuprates, and point to a new direction in search of new high-Tc superconductors.
Keynote Forum
Gennadiy Filippov
Chuvash State Pedagogical University, Russia
Keynote: Passage of accele4rated high charged ions through a system of parallel thin films
Time : 16:45-17:10
Biography:
Gennadiy Filippov has his expertise in particle-solid interaction physics. He has completed his PhD at the age of 54 years from Tomsk State University (Russia). He is head of the Laboratory of Biophysics and Bio-nanotechnology in the Chuvash State Agricultural Academy and Professor in the Chuvash State Pedagogical University in Cheboksary, Russian Federation.
Abstract:
The passage of charged projectiles through the porous structure is investigated for the goal of calculation the forced action of a wave packet (or the classical particle bunch) on the porous walls. An analysis of the passage of quantum particles is performed by numerically solving the Schrödinger equation. In the framework of classical electrodynamics, the polarization force acting on the charge is calculated. In the problem of the passage of ions with large values of charges through ultrathin carbon films, the possibility of pore performing in the films is analyzed. In order to understand the process more clearly, a mathematical modeling of the film is performed, accompanied by a clarification of the most important polarization properties. Calculations showed the possibility of perforating the film due to the influence of ponderomotive forces generated by the strong polarization field of the wave packet of the passing ion.
Keynote Forum
Joseph Poon
University of Virginia, USA
Keynote: Amorphous magnetic films for spintronics
Biography:
Joseph Poon is William Barton Rogers Professor of Physics at the University of Virginia. He received his BS and PhD from Caltech and was did postdoc work at Stanford University. He has published 200+ papers. His current research is on magnetic films and thermoelectric materials. He previously worked on metallic glasses and quasicrystals.
Abstract:
Spintronics (SPIN TRansfer elecTRONICS) was introduced by SA Wolf in 1996 as the name of a DARPA project to develop both a non-volatile magnetoresistive random access memory (MRAM) and also magnetic sensors for specialized applications. Today, spintronics has already shown promise in ultra-low power and non-volatile information processing and data storage technology. A recent advance in spintronic material systems will be reviewed. For the rest of my talk, I will focus on amorphous rare-earth-transition-metal (a-RE-TM) thin films that exhibit perpendicular magnetic anisotropy (PMA). a-RETM are ferrimagnets with two ferromagnetic RE and TM sublattices that interact via antiferromagnetic exchange coupling. These amorphous ferromagnetic films exhibit large coercivity fields of several Tesla and moderate anisotropy energy ~106 erg/ cm. The magnetization of the sublattices compensates each other at the compensation temperature (Tcomp). The spin structure and atomic-scale structure support ultrafast magnetic switching and ultra-small ~5-10 nm skyrmions. These materials are being studied for high-density ultrafast nanoelectronics. Self-exchange bias can be obtained by appropriately configuring the nanoscale structure. The mechanisms are verified by micromagnetic and atomistic simulations. Measurements include magnetization, MOKE, MFM, Hall effect, and magneto-resistance. The ability to control these new properties in amorphous films without the need for epitaxial growth could open a new avenue for enhancing the functionalities of spin-based materials.
Session Introduction
I Chávez
Universidad Nacional Autónoma de México, México
Title: Cooper pairs in superconductivity in a generalized BEC theory
Biography:
I Chávez MS and BS have completed his Doctoral degree in the Material Sciences and Engineering Research Graduate Program at the National Autonomous University of Mexico (UNAM, in Spanish) with the thesis titled “A new dimensionless coupling constant in superconductivity.” He is also a Laboratory Assistant at the School of Sciences at UNAM.
Abstract:
The generalized Bose-Einstein condensation (GBEC) theory subsumes as special cases both BCS and BEC, among other theories. It hinges on three separate new ingredients: i) treating Cooper pairs (CPs) as actual bosons as distinct from BCS pairs which strictly speaking are not bosons; ii) inclusion of two-hole Cooper pairs (2hCPs) on an equal footing with the usual two-electron ones (2eCPs); and iii) incorporating in the resulting ideal ternary boson-fermion (BF) gas specific vertex interactions that drive formation/dis-integration processes of both kinds of CPs. Here we extend the BCS-Bose crossover theory by explicitly including 2hCPs. This leads to a phase diagram with two pure phases, one with 2eCPs and the other with 2hCPs, plus a mixed phase with arbitrary proportions of both. The special-case phase with a 50-50 mixture of both 2e/2hCPs gives the usual unextended BCS-Bose crossover theory. Furthermore, if Tc and TF are respectively the critical and the Fermi temperatures, it predicts Tc /TF values for the elemental superconductors Al, In, Sn, Pb, Hg, and Nb comparing quite well with experiment and notably much better than BCS predictions. Also shown is a phase diagram of the dimensionless energy gap at zero-temperature Δ(0)/EF vs n/nf , where EF =kB TF is the Fermi energy. We do this for the 50-50 case as well as for the pure 2eCPs and 2hCPs cases separately. It is thus unequivocally shown that if one ignores 2hCPs the energy gap lies substantially below the 50-50 case which already roughly reproduces the data.
Moussab Harb
King Abdullah University of Science and Technology, Saudi Arabia
Title: Toward rational design of new photocatalytic materials for solar fuel generation using density functional theory
Biography:
Moussab Harb has completed his PhD in 2008 at the age of 25 years from Light-Matter Institute (ILM) at Claude Bernard University (UCBL-France). Until 2014, he has completed several Postdoctoral research studies from Multidisciplinary Research Institute on Environment and Materials (IPREM-France), French Petroleum Institute (IFPEN-France) and KAUST Catalysis Center (KCC-KSA). He is currently a Research Scientist in Computational Physical Chemistry for solar Energy Conversion at KAUST University working on the Design of new potential and efficient 3D and 2D materials for visible-light-driven photocatalytic water-splitting and photovoltaic devices using accurate first-principles quantum calculations. He has published more than 50 papers in peer-reviewed journals and has been serving as a member of ACS, APS, AIP and MRS societies and reviewer of many relevant scientific journals.
Abstract:
Solar hydrogen production through the challenging photocatalytic water splitting using powder semiconductor materials still remains a promising technology due to the low cost required. Designing new potential absorber semiconducting materials used in visible-lightdriven photocatalytic water splitting cells requires the appropriate determination of different components that will be assembled in the final device. In addition to the required good chemical stability in aqueous solution, high crystallinity and adequate band gap energy of the prepared material (greater than 1.23eV and near 2.0eV) to absorb a wide range of photons in the visible region, which counts for 43% of the solar spectrum, other specific intrinsic parameters directly involved in the processes must be properly tuned. They include the solar light absorption intensity, exciton binding energy, the possibility of charge carrier diffusion throughout the crystal structure to the surface and their interaction with the solution. Experimentally, previous works on semiconductors widely used in photovoltaic devices revealed that high dielectric constant is needed to obtain a good ability for exciton dissociation into free holes and electrons at room temperature. A delocalization orbital character of photogenerated charge carriers is also required to give low effective masses and help for their good transport to the surface by minimizing the electron-hole pairs recombination. Moreover, suitable valence band (VB) and conduction band (CB) edge positions with respect to water redox potentials are also needed to give the driving force to the photogenerated holes and electrons to oxidize water and to reduce H+. To design and characterize new materials for solar energy conversion applications, the density functional theory (DFT) has emerged as a valuable computational tool to quantify these key intrinsic parameters because of the difficulties to their direct experimental measurement. Achieving accurate DFT computations is thus particularly relevant, and this is known to be in strong correlation with the type of the exchange-correlation functional used to describe the various electron-electron interactions. In previous theoretical studies on largely utilized semi-conducting materials in photocatalytic water splitting and photovoltaics, we have shown that the intrinsic parameters mentioned above can be predicted with good accuracy using DFT along with the screened Coulomb hybrid Heyd−Scuseria−Ernzerhof (HSE06) functional. Following this robust computational protocol, we have shown suitable band edge positions for visible-light-driven overall water splitting of (Ta3-xN5-5x)O5x (x≥0.16) compounds. Besides, we have predicted interesting dielectric, charge carrier transport and redox features of (Ta1-xNbx )ON solid solution materials (0.25≤x≤0.5) for water splitting while they revealed almost UV light absorption features due to their large predicted direct bandgaps in the 2.8-3.0eV range. Recently, we have predicted Ta0.75V0.25ON as a promising photocatalyst for splitting of water driven by solar light, with an adequate band gap of 2.0eV, high absorption efficiency, a static dielectric constant greater than 10, smaller hole and electron effective masses than 0.5 m0 along the [001] and [010] crystallographic directions respectively, binding energy of the exciton lower than 25meV, and suitable energy levels of band edges for water splitting limits. The obtained solar energy absorption and redox features of Ta0.75V0.25ON were clearly better than those acquired for Ta3 N5 , which is the most common semiconductor photocatalyst used in visible-light-driven water splitting. In my talk, I will first show how DFT can greatly help the experimentalists for a rational design of new photocatalytic materials for solar energy conversion by giving relevant information on key and recent examples. Secondly, I will present a deep DFT-based computational study successfully achieved recently in combination with experiment aiming to understand the nature of the trap states that are significantly decreased upon hydrogen treatment and explain the electronic origin of the charge carrier lifetime enhancement in bismuth vanadate (BiVO4 ) through mild hydrogen treatment. Overall, these findings provide further insights into the interplay between defect modulation and carrier transport in metal oxides, which benefit the development of low-cost and highly-efficient solar energy conversion devices.
Sabur Abiodun Ayinde
The Federal Polytechnic, Nigeria
Title: Fabrication and characterization of copper doped cadmium sulphide thin film solar cell
Biography:
Sabur Abiodun Ayinde is a PhD student at Obafemi Awolowo University where he had his masters in Engineering Physics in 2015. He is a 33 years academic staff of The Federal Polytechnic, Ede, Nigeria. He has worked in a manufacturing industry after the graduation of his first degree and has spent the past 7 years of his life as a polytechnic teacher. He has attended a series of conferences and has published more than 8 papers in reputed journals. In his quest to know how things work, he likes to solve challenging problems in materials and solid state electronics. He is happily married with a kid and has always had the desire to render community services to the people.
Abstract:
The fabrications of electronic components, especially solid-state devices and microelectronic integrated circuits, have undoubtedly found the widest and most demanding applications for thin-film depositions. With a view to fabricating a solar cell, a prepared precursor of Copper Cadmium dithiocarbamate was used for the deposition of CuCdS thin films at 420o C on ITO coated glass substrate by MOCVD technique as the absorber layer. Aluminium doped Zinc Oxide (AZO) was also deposited by spray pyrolysis at 350o C as the window layer on the deposited absorber layer. Silver paste was drop-dried on the deposited window layer as the ohmic contact. The result of the deposited layered thin films and the solar cell were analyzed using Rutherford Backscattering Spectroscopy and Energy Dispersive X-ray (EDX), UV Visible spectrophotometer, Keithley fourpoint probe instrument, and I-V analysis. The RBS analysis of the deposited CuCdS film revealed the percentage composition of Cu=4.20%, Cd=10.77%, S=33.74%, and O=51.27%. Film thicknesses of 133nm and 889nm were recorded for AZO and CuCdS thin film respectively as obtained from the RBS analysis. The composition of AZO as observed by EDX is Al=1.13%, Zn=66.40%, and O=21.61%. The UV-visible analysis of AZO film revealed that the film had an optical transmittance of 60% in the visible portion of the spectrum with a direct bandgap of 3.25eV, while bandgap of CuCdS is 2.41eV. The absorbance of the CuCdS film was observed to be low in the VIS/NIR regions and high in UV region. The sheet resistance and resistivity of AZO film are 9.58×106 Ω/square and 1.27×10-2 Ωcm respectively, while 1.17×109 Ω/square and 10.40Ωcm were obtained as the sheet resistance and resistivity of CuCdS film respectively. The I-V analysis of the fabricated solar cell showed that, under dark condition, it behaves like a diode or semiconductor current rectifier. The fill factor as extracted from the device and its corresponding conversion efficiency are 0.6911 and 4.38% respectively
Ogundola Sunday
Federal College of Education, Nigeria
Title: Determination of mechanical, structural and thermodynamic properties of halfheusler compound (Zirconium Lead Palladium) in solid state physics
Biography:
Ogundola Sunday hails from Irele LGA, Ondo State of Nigeria. He bags BSc Ed in physics from Obafemi Awolowo University, Ile-Ife, Nigeria. He has MSc in Theoretical Physics from University of Benin, Nigeria. He has written some reputed the University-based journals in Nigeria. He is currently a Physics Lecturer at Federal College of Education, Eha-Amufu, Enugu state, Nigeria. He is eagerly opting for his PhD in University of Benin, Nigeria. He is happily married with three children.
Abstract:
Half-Heusler compounds are promising semi-conductors which are environmentally friendly and of low-cost thermoelectric materials. They have a high figure of merit. Half-Heusler (HH) alloys are among the most promising novel thermoelectric (TE) materials intended for mid-to-high temperature power generation applications. They are members of the vast family of Heusler alloys with the general composition X2 YZ, consisting of three interpenetrating face-centered cubics (fcc) sub-lattices (Wang et al., 2016). Zirconium Lead Palladium (ZrPdPb) is one of the examples of the Half-Heusler alloy that crystalizes in the face-centered cubic structure with the space group F4-3m (Koller et al., 2009).In this work, the structural, mechanical and thermodynamic properties of ZrPdPb were investigated by the first-principle calculations using Quantum Espresso that implements the Density Functional Theory (DFT). The results indicate that all Half-Heusler compounds are narrow-gap semiconductors. The results of Young’s modulus, elastic constants C11, C12 and C44, Shear modulus, and Lattice constants, Bulk modulus and pressure derivative which constitute the mechanical and structural properties respectively of ZrPdPb are in good agreement with the results in the literature. The thermodynamic properties of ZrPdPb such as Heat capacity, internal energy, entropy, free energy, Debye temperature etc. were calculated using Quantum Espresso. It is seen that at room temperature i.e. 300k, the internal energy is 23.15kJ/(molk), and the heat capacity is 72.27kJ/(molk). The Debye temperature is found to be 365.3K. From 500K and above, the heat capacity approaches an asymptotic value of 37J/mol/K and obeys DulongPetit law which states that at high-temperature Specific heat capacity of a substance remains constant. Also, at sufficiently low temperature, the specific heat capacity is proportional to T3 . The heat capacity of ZrPdPb shows that the Half-Heusler alloy has little electrical and thermal conductivity as greater heat energy is required to break the intermolecular forces. The mechanical properties ZrPdPb show that the material is not stable under heavy vibration. Suggestions were made to improve the mechanical and thermodynamic properties. Other properties like the magnetic and optical properties of ZrPdPb should be studied. The electrical, mechanical and structural properties of ZrPdPb should be studied by alloying. The electronic, mechanical, structural, magnetic properties of ZrPdPb should also be studied under pressure.
Biography:
Dieter M Gruen received his PhD at the University of Chicago in Chemical Physics. He is an Argonne Distinguished Fellow, Emeritus and President of Dimerond Technologies LLC. He is an internationally recognized scientist and innovator with more than 400 publications.
Abstract:
The conversion of light to electricity can be done indirectly by first converting light to high-temperature heat and then heat to electricity or directly using solar cells. These processes are today carried out on a large scale in physically separate solar plants. The indirect process is limited by the thermodynamically dictated Carnot efficiency while the direct conversion efficiency has an upper bound the Shockley-Queisser limit. Is there a way to overcome these efficiency limitations without violating physical laws? Clearly, a way dramatically to lower solar electricity costs would be to combine both processes in a single solar power plant facility without substantially increasing its capital cost. Such a hybrid procedure would effectively double the conversion efficiency but it would require the use of solar cells that operate at 400 Centigrade or above. Such cells do not exist today and therefore this attractive approach cannot be implemented. This presentation focuses on recent breakthrough developments in condensed matter physics and chemistry that are anticipated to lead to the creation of a new generation of high-temperature solar cells. Spectacular advances have occurred in the synthesis and nanophotonics of wide band-gap (WBG) semiconductors as well as in understanding the unique quantum electrodynamic properties of graphene for which the 2010 Nobel Prize in Physics was awarded. The p/n heterojunctions between these two materials are predicted to allow very effective separation of electron/hole pairs formed in graphene by the absorption of the total solar spectrum waveguided along the length of the WBG nanowires. These materials were selected because their electronic structures are influenced only minimally by increasing temperature and because these materials are not resource limited as well as being environmentally benign.
Eugene Stephane Mananga
The City University of New York, USA
Title: Using the floquet-magnus and the Fer expansion approaches to control the spin dynamics in solid-state nuclear magnetic resonance and beyond
Biography:
Eugene Stephane Mananga is the Deputy Executive Director of The CUNY ACADEMY FOR HUMANITIES AND SCIENCES, and a member in the Board of Directors-at-Large of The ACADEMY. He is a Faculty Member in the Physics & Chemistry Doctorate Programs at the Graduate Center of the City University of New York. He is an Assistant Professor of Physics and Nuclear Medicine at BCC of CUNY, and an Adjunct Professor of Applied Physics at New York University. He completed his Ph. D in Physics from the Graduate Center of the City University of New York, and holds 6 additional graduate degrees and training from various institutions including Harvard University, Massachusetts General Hospital, and City College of New York.
Abstract:
The topic of the talk opens a way to an infinite number of suggestions. However, it is very important to remember that the spin dynamics have recently found new major areas of applications such as topological materials. Researchers, dealing with those new applications, are not usually acquainted with the achievements of the magnetic resonance theory, where those methods were developed more than thirty years ago. They repeat the same mistakes that were made when the methods of spin dynamics and thermodynamics were developed in the past. This talk focused on the spin dynamics in solid-state nuclear magnetic resonance (NMR) and beyond. This presentation is very useful not only for the NMR, physical, and chemical physics communities but for the new communities in several younger fields. It will be very useful for scientists working in different directions. In this talk, I will present the use of the Floquet-Magnus expansion and the Fer expansion approaches for the calculation of effective Hamiltonians and propagators in solid-state NMR. These approaches are very important and contribute theoretically and numerically in the general field of spin dynamics and chemical physics.
- Condensed Matter Physics | Superconductivity and Superfluidity | Solid State Physics | Materials Physics Session Chai
Location: Los Angeles
Chair
I Chávez
Universidad Nacional Autónoma de México, México
Co-Chair
Moussab Harb
King Abdullah University of Science and Technology, Saudi Arabia