Banca de DEFESA: LUCAS RODRIGUES DELGADO DE FREITAS

Uma banca de DEFESA de MESTRADO foi cadastrada pelo programa.
STUDENT : LUCAS RODRIGUES DELGADO DE FREITAS
DATE: 26/03/2021
TIME: 10:00
LOCAL: Plataforma Google Meet
TITLE:

Gapless excitations in Kitaev materials with defects

KEY WORDS:

Kitaev model, quantum spin liquids, Majorana fermions, mean field, nuclear relaxation rate.

PAGES: 61
BIG AREA: Ciências Exatas e da Terra
AREA: Física
SUMMARY:

A quantum spin liquid is a magnetic phase of matter remarkable for its ground state long-range entanglement and fractional excitations. A quantum spin liquid appears in the well-known Kitaev honeycomb spin-half model. In a magnetic field, there is a phase transition to a topological phase with an energy gap in the bulk and chiral Majorana fermions at the edge However, recent nuclear magnetic resonance experiments suggest excitations without a gap in this phase, signalled by a power-law dependence of the spin-lattice relaxation rate at low temperatures. In this work, I propose a mechanism to account for this experimental result. I use the localization of chiral Majorana modes in defects to explain the presence of gapless modes in the bulk. Treating the weak interaction between the chiral modes in the defects within a mean-field approximation, I find that these modes remain gapless when the interaction is below a critical value that depends on the magnetic field strength. I used the effective low-energy theory to calculate the spin-lattice relaxation rate and found a behavior that agrees with the experimental result.

BANKING MEMBERS:
Externo à Instituição - EDUARDO MIRANDA - UNICAMP
Interno - 2411793 - LEONARDO DANTAS MACHADO
Presidente - 1313663 - RODRIGO GONCALVES PEREIRA