Seminars & Colloquia

Using Quantum Mechanics Change-of-Basis Problems to Explore Students’ Meta-Representational Competence
Idris Malik

Ph.D. Candidate,
Physics, NDSU

Monday, April 7, 3:00-4:00pm, South Engineering 208

Refreshments at 2:30, South Engineering 208 (for online link contact Alexander Wagner)

Abstract:

Meta-Representational Competence (MRC) is a theoretical framework that is used to analyze how people create and interact with external representations. Here, we refer to “MRC” as the theoretical framework and “MRC concepts” as statements or ideas that we analyze under the theoretical framework. While the MRC framework has been extensively used in Research in Undergraduate Mathematics Education, it has not been widely leveraged outside its home discipline. We highlight a potential for MRC to lead to productive research study designs and analysis of data involving MRC concepts, using our study, which is rooted in the MRC framework.

Within Quantum Mechanics, problems may be approached or perceived differently based on the notation used (either Dirac, Matrix, or Spinor notation) in the problem statement or by the person working on the problem. Semi-structured interviews were conducted to present physics students with change-of-basis content problems. These content questions were used to ask students about MRC concepts directly. Student statements were coded to revise previously identified facets of MRC and define novel facets present in our data. Our analysis of three student interviews demonstrates an array of utility of MRC concepts in students, solidifies MRC as a useful lens for investigating student thinking, and suggests that specific instruction on MRC concepts could be worthwhile for expert-like skill development and conceptual understanding.

Author bio:

Idris Malik is a 2nd year Ph.D. student in the Physics and Discipline-Based Education Research program at NDSU. He received his BS in Physics at The Ohio State University, where he did quantitative work with Dr. Andrew Heckler. Idris now works on qualitative research with Dr. Warren Christensen at the boundary of Math and Physics. Current projects include investigating how students think and talk about Calculus topics in Calc-Based Intro-Physics courses, and designing modular curricular materials for middle-division math topics used in upper-division physics. He is also involved in collaborative projects in the NDSU DBER community. Beyond NDSU, Idris serves as the Graduate Student Representative and Physics Education Research Consortium of Graduate Students (PERCoGS) Liaison for the Physics Education Research Leadership and Organizing Council (PERLOC).

Phonon-Mediated Relaxation from Including Non-adiabatic Couplings of Time-domain DFT in Kadanoff-Baym-Keldysh Technique
Hadassah Griffin

Ph.D. Candidate,
Physics, NDSU

Monday, December 2, 3:00-4:00pm, South Engineering 208

Refreshments at 2:30, South Engineering 208 (online visit)

Abstract:

Applications of heterostructured nanomaterials, such as Janus semiconductor nanocrystals (NCs), require a quantitative understanding of their photoexcited properties. Here, we study photoexcited state time evolution of a Si QD, a reference PbSe NC, and several 1.9 nm Janus NCs made of Cd, Pb, and Se by employing the Boltzmann transport equation (BE), which allows for competition between different relaxation channels such as phonon-mediated carrier thermalization, exciton transfer, and exciton multiplication and recombination. BE collision integrals are computed using finite-temperature many-body perturbation theory (sometimes called Kadanoff-Baym-Keldysh (KBK) technique) based on density functional theory (DFT) simulations. Exciton effects are included by solving the Bethe-Salpeter equation, with additional simplifying approximations, and incorporating exciton energies and states into the collision integrals. Phonon-mediated relaxation is included by utilizing on-the-fly nonadiabatic coupling data from DFT-based finite-temperature molecular dynamics simulations in the KBK technique. Rates calculated from the collision integrals can be used to calculate internal quantum efficiency (the number of excitons generated from a single absorbed energetic photon).

Author bio:

Hadassah Griffin is a PhD student at the North Dakota State University Department of Physics. Her research advisor is Dr. Andrei Kryjevski. She started her B. S. Physics degree at Brigham Young University in Provo and completed it at Brigham Young University---Idaho in 2021. She obtained her M.S. in Physics from North Dakota State University in May 2024.

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