CM/BIO/ECE Seminars

The combined Condensed Matter/Biological Physics/Electrical and Computer Engineering Seminars take place every Wednesday at 4 PM in the Physics Library (rm 223A, Physics Bldg.)

Date Speaker/Title/Abstract
4/17/24 Dr Damon Farmer
CM Seminar
4/16/24 Dr Damon Farmer
CM Seminar
12/6/23 Dr Sheng Ran
CM Seminar
11/8/23 Professor Tara Finegan
CM Seminar
10/18/23 Dr. Didarul Alam, University of Missouri
Electron Correlation Effects in Solid-state High Harmonic Generation with First-Principles Calculations

High harmonic generation (HHG) is an extreme non-linear phenomenon where strong laser-field pulses interact with a medium to produce coherent and high-frequency harmonics of the incident light.  Since its first observation in solids in 2011, pioneering theoretical studies have clarified some of the details of the microscopic mechanism behind this phenomenon, like the role of intra- and inter-band transitions, the contribution of the transition dipole moments to the even and odd harmonic peaks, effects of broken symmetry, etc. However, the role of electron correlation effects in the HHG in strongly correlated materials is much less understood. This talk will discuss the role of these effects in the high-harmonic (HH) spectra of solids, using time-dependent density-functional theory and dynamical mean-field theory, for the examples of semiconductor ZnO, perovskites BaTiO3 and BiFeO3 and transition-metal oxide VO2. It is found that correlation effects significantly modify the HH spectrum of all systems, in particular through the ultrafast modification of the electronic spectrum in ZnO. In the case of BaTiO3, correlation effects generate "super-harmonics" – periodic enhancements and suppressions of specific harmonic orders that depend on the correlation strength. Memory effects in HHG were found to lead to a further extension of the harmonic cutoff. For the HH spectrum of VO2,  we find correlation-induced higher harmonics, in good agreement with experimental data. The obtained results shed light on the role of electron correlations in the HH spectrum in complex materials and may help pave the way for future advancements in the field of ultrafast science and attosecond physics.

11/2/22 Prof. Yew San Hor, Missouri S&T
Search for New Quantum Materials

Quantum materials such as topological, 2D and nanostructured materials have attracted tremendous attention due to their exotic quantum properties. In this presentation, we will talk about our findings of chemical doping effect in inducing magnetism and superconductivity in chalcogenide compounds. Several interesting physical properties have been observed such as the anomalous Hall effect in Cr-doped Sb2Te3, metamagnetic behavior in Fe-doped Bi2Se3, and the coexistence of ferromagnetism and superconductivity in Nb-doped Bi2Se3 single crystals. We will also present results of the synthesis and characterization of superconducting TaS2 nanowires. Our approach includes the synthesis of 1D charge-density-wave (CDW) TaS3 nanostructure precursors followed by the nondestructive and controlled adjustment of the S composition. TaS3 nanowires show the canonical CDW behavior, but the converted TaS2 nanowires show superconductivity and vortex avalanche behaviors at temperatures below its Tc ~ 3.8 K, which is about three times higher than that of 2D bulk TaS2 crystals. Physical properties of polycrystalline Zn1-xCrxTe samples will also be presented. The samples show metallicity and ferromagnetic behavior for higher Cr doping concentration. Furthermore, optical transparency in the visible light range of these polycrystalline ferromagnetic Zn1-xCrxTe was found to be 40% - 85% for Cr doping concentration up to x = 0.18.