BEGIN:VCALENDAR
VERSION:2.0
PRODID:Icfo
X-PUBLISHED-TTL:P1W
BEGIN:VEVENT
UID:69d4b3c5a8982
DTSTART:20250611T080000Z
SEQUENCE:0
TRANSP:OPAQUE
LOCATION:ICFO Auditorium
SUMMARY:ICFO | EMMANUEL BAFFU AMUAH
CLASS:PUBLIC
DESCRIPTION:Strongly-correlated materials have emerged as one of the most a
 ctive areas of research in Condensed Matter Physics. Interests in these ma
 terials arise mainly from the pliability of their properties\, offering th
 e possibility of tailoring these materials for specific applications. This
  is\, in turn\, due to the rich interplay of interactions between electron
 ic\, orbital and lattice degrees of freedom. This complex coupling of the 
 different degrees of freedom\, on the other hand\, makes strongly-correlat
 ed materials difficult to understand.\nUltrafast spectroscopy offers the p
 ossibility of resolving this bottleneck and provides insight into aspects 
 of correlated materials crucial for enhancing our understanding of these m
 aterials. One such aspect is photoinduced phase transitions\, where light 
 drives a symmetry change in a material. To date\, research has focused on 
 using light to force materials to cross a single structural transition. In
  this work\, we investigate the possibility of making multiple phase jumps
  with a single pulse of light. A suitable system for such study is the man
 ganite\, Pr0.5Ca1.5Mn04\, which despite its prospects remains less explore
 d. This layered manganite exhibits multiple phase transitions of electroni
 c\, orbital and structural origins\, as a function of temperature. The pre
 sence of more than one phase transition in Pr0.5Ca1.5Mn04 allows us to exa
 mine the possibility and mechanism of multi-phase transition\, an aspect o
 f photoinduced phase transition that has hitherto not received much attent
 ion. The physics of the manganites is strongly dictated by the dynamics of
  Jahn-Teller phonons\, which occur at a very high frequency (&gt\;15 THz).
  Studies involving these phonons thus call for setups with a very high tim
 e resolution.\nThis thesis first discusses the construction of a novel set
 up that makes use of few-cycle pulses from the visible to the near infrare
 d wavelength regions. Then\, leveraging on the capabilities of this setup\
 , we undertake ultrafast measurements on Pr0.5Ca1.5Mn04 in two parts: the 
 linear and nonlinear pumping regimes. In the linear regime\, we perform br
 oadband\, low-fluence measurements to characterize the sample. From this\,
  we identify key structural and electronic changes that occur during the t
 hermal transition pathway\, allowing us to map out the sample into differe
 nt symmetry regions\, in agreement with literature. In the nonlinear pumpi
 ng regime\, we study the fluence dependence of the changes identified from
  the linear regime. By analyzing the coherent lattice response\, we find i
 ndications of both single and double phase transitions occurring.\n&nbsp\;
 \nWednesday June 11\, 10:00 h. ICFO Auditorium \nThesis Directors: Prof. D
 r. Simon Elliot Wall and Dr. Allan Stewart Johnson
DTSTAMP:20260407T073533Z
END:VEVENT
END:VCALENDAR