What is the minimal condition for a phonon to couple to a magnetic field and bend its trajectory?

• Grant number: 24/16100-9
• Support Opportunities: Regular Research Grants
• Start date: December 01, 2024
• End date: November 30, 2029
• Field of knowledge: Physical Sciences and Mathematics - Physics - Condensed Matter Physics
• Principal Investigator: Valentina Martelli
• Grantee: Valentina Martelli
• Host Institution: Instituto de Física (IF). Universidade de São Paulo (USP). São Paulo , SP, Brazil

Abstract

The thermal Hall effect (THE) is the thermal analogue of the Hall effect, where a charge flow changes the trajectory because of the Lorentz force by applying a perpendicular magnetic field. Compared to the Electronic Hall effect, which has been investigated in depth and is frequently employed to detect exotic electronic states, THE is still not understood from a fundamental standpoint despite having been observed in a growing number of materials. When the THE is observed in an insulator, phonons (or possibly any other neutral heat carriers), which are charge-less and spin-less excitations, are said to acquire handedness. Both intrinsic (thermal carriers coupled to field-sensitive mechanism) and extrinsic mechanisms (impurities and defects) have been put forward to explain this phenomenon. Exotic chargeless excitations (ex. Majorana fermions), which are expected to open a gap in their bands under the effect of a magnetic field, were predicted to show a peculiar signature on THE. In this project, we will perform a systematic investigation of THE down to low temperatures (1.5-300K) and under a magnetic field up to 9T on a series of naturally occurring crystals with a controlled degree of impurities, of sample crystallinity, and structural chirality. The experiments will be carried out on home-made platforms and are expected to provide new relevant insights and advance the understanding of the minimal conditions needed for a phonon to bend in the presence of a magnetic field. (AU)

Scientific publications

(References retrieved automatically from Web of Science and SciELO through information on FAPESP grants and their corresponding numbers as mentioned in the publications by the authors)

HENRIQUES, ALEXANDRE; LIMA, MARIANA S. L.; NILSEN, GORAN J.; GUTMANN, MATTHIAS J.; WIRTH, STEFFEN; BRITO, WALBER H.; MARTELLI, VALENTINA. Anomalous Glassy Thermal Conductivity in a Perovskite Bismuthate Induced by Structural Dynamic Instability. ADVANCED SCIENCE, v. N/A, p. 10-pg., 2025-06-04. (21/00989-9, 24/00177-2, 22/01742-0, 22/14202-3, 18/19420-3, 18/08845-3, 19/17874-0, 24/16100-9)