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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 721 records · Page 40
All sourcesNASA NTRSDOE OSTI
DOE OSTI2022

Magnetic Control of Soft Chiral Phonons in PbTe

We report PbTe crystals have a soft transverse optical phonon mode in the terahertz frequency range, which is known to efficiently decay into heat-carrying acoustic phonons, resulting in anomalously low thermal conductivity. Here, we studied this phonon via polarization-dependent terahertz spectroscopy. We observed softening of this mode with decreasing temperature, indicative of incipient ferroelectricity, which we explain through a model including strong anharmonicity with a quartic displacement term. In magnetic fields up to 25 T, the phonon mode splits into two modes with opposite handedness, exhibiting circular dichroism. Their frequencies display Zeeman splitting together with an overall diamagnetic shift with increasing magnetic field. Using a group-theoretical approach, we demonstrate that these observations are the result of magnetic field-induced morphic changes in the crystal symmetries through the Lorentz force exerted on the lattice ions. Thus, our Letter reveals a novel process of controlling phonon properties in a soft ionic lattice by a strong magnetic field.

36 MATERIALS SCIENCE↗
DOE OSTI2024

Directed Flow and the Chiral Magnetic Effect in Ultrarelativistic Collisions with CMS at the LHC (Final Technical Report for DOE Grant # DE-SC0021080)

This Final Technical Report covers the years of activity for the Grant DE-SC0021080. It reflects the efforts of Alice Mignerey, the PI, Timothy Koeth, the co-PI, graduate students Eric Adams and Samuel Lascio, and undergraduates Alyssa Marinelli and Max Bernard. Results from three separate aspects of the project are presented: 1) understanding the radiation damage of the positive and negative sides of the Spectator Reaction Plane detector (SRPD) for data from the 2018 PbPb run at the CERN LHC. 2) Results of the directed flow in PbPb collisions at $\sqrt{SNN}$ = 5.02 TeV. 3) Activation studies of the sectors of the positive side of the SRPD and radiation damage studies on fused quartz using the Maryland 4-MeV electron accelerator. The most significant result is that the reaction plane derived directed flow for both participant and spectator reaction planes is many times larger than that obtained by ALICE.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2024

Directed Flow and the Chiral Magnetic Effect in Ultrarelativistic Collisions with CMS at the LHC (Final Technical Report for DOE Grant # DE-SC0021080)

This Final Technical Report covers the years of activity for the Grant DE-SC0021080. It reflects the efforts of Alice Mignerey, the PI, Timothy Koeth, the co-PI, graduate students Eric Adams and Samuel Lascio, and undergraduates Alyssa Marinelli and Max Bernard. Results from three separate aspects of the project are presented: 1) understanding the radiation damage of the positive and negative sides of the Spectator Reaction Plane Detector (SRPD) for data from the 2018 PbPb run at the CERN LHC. 2) Results of the directed flow in PbPb collisions at √sN N = 5.02 TeV. 3) Activation studies of the sectors of the positive side of the SRPD and radiation damage studies on fused quartz using the Maryland 4-MeV electron accelerator. The most significant result is that the reaction plane derived directed flow for both participant and spectator reaction planes is many times larger than that obtained by ALICE.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗