ELFT HÍRADÓ

[Andras Palyi <palyi AT mail.bme.hu>]

Dear Colleagues,

Next Monday György Frank will give a talk at the BME Exotic Quantum Phases 
seminar:

Speaker: György Frank (BME)
Title: Magnetic degeneracy points in interacting two-spin systems: 
geometrical patterns, topological charge distributions, and their stability
Time: Mar 9, 2020, Monday, 14:00 (sharp)
Location: seminar room of the theory department (Department of Theoretical 
Physics, Building F, stairway III., 1111 Budapest, Budafoki ut 8.)

Abstract: "Spin systems are described by the exchange interaction between the 
spins, the Zeeman interaction with an external magnetic field, and the 
spin-orbit interaction. In these systems we can often find magnetic field 
values where the ground state is degenerate. Often these are described as 
Weyl points or diabolical points, and they carry topological charge. We point 
out that in general, the number of these points can depend on the system 
parameters [1], moreover, the degeneracies are not necessarily isolated 
points, but can also form a closed curve or a closed surface [2]. We give an 
analytical formula for the locations of the ground-state degeneracies, and we 
calculate the topological charge distributions of the possible geometrical 
patterns, and investigate their stability. Our findings are relevant for spin 
qubit control and readout in double (or multiple) quantum dot systems.

[1] Z. Scherübl et al., Comms. Phys. 2, 108 (2019).
[2] Gy. Frank et al., https://arxiv.org/abs/1910.02831”

Best regards,
Andras Palyi