ELFT HÍRADÓ

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

Dear Colleagues,

Next Monday Zoltán Okvátovity will give a talk at the BME Exotic Quantum 
Phases seminar:

Speaker: Zoltán Okvátovity (BME)
Title: Out-of-time-ordered commutators in Dirac--Weyl systems
Time: Mar 2, 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: "Quantum information stored in local operators spreads over other 
degrees of freedom of the system during time evolution, known as scrambling. 
This process is conveniently characterized by the out-of-time-order 
commutators (OTOC), whose time dependence reveals salient aspects of the 
system's dynamics. Here we study the spatially local spin correlation 
function i.e., the expectation value of spin commutator and the corresponding 
OTOC of Dirac--Weyl systems in 1, 2 and 3 spatial dimensions. The OTOC can be 
written as the square of the expectation value of the commutator and the 
variance of the commutator. The problem features only two energy scales, the 
chemical potential, and the high energy cutoff, therefore the time evolution 
is separated into three different regions. The spin correlation function 
grows linearly with time initially and decays in a power-law fashion for 
intermediate and late times. The OTOC reveals a universal t^2 initial growth 
from both the commutator and the variance. Its intermediate and late time 
power-law decays are identical and originate from the variance of the 
commutator. These results indicate that Dirac--Weyl systems are slow 
information scramblers and are essential when additional channels for 
scrambling, i.e. interaction or disorder are analyzed. Reference: 
https://arxiv.org/abs/1909.09376";

Best regards,
Andras Palyi