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SUMMARY:IMX Colloquium - Time domain THz spectroscopy: a powerful tool to 
 study magnets and superconductors
DTSTART:20260323T131500
DTEND:20260323T141500
DTSTAMP:20260430T181903Z
UID:72a2f45368fcb3b1febf6d24ad455d79fdc12c35897c00258ad4072d
CATEGORIES:Conferences - Seminars
DESCRIPTION:Prof. Chiara Ciccarelli\, University of Cambridge\, UK\nI wil
 l divide my talk into two parts\, which illustrate the main scientific que
 stions we are tackling by using time domain THz spectroscopy.\n\n1) Genera
 ting ultra-fast spin currents is important in the context of ultra-fast ma
 gnetic memories. In the first part of the talk I will discuss our work on 
 using antiferromagnets as efficient emitters of sub-picosecond spin curren
 t pulses\, despite the net-zero magnetisation. I will present our work on 
 the optically induced picosecond spin transfer from magnetically compensat
 ed magnets\, including antiferromagnets and ferromagnetic alloys\, to Pt u
 sing time-domain THz emission spectroscopy. We will focus on three studies
  in antiferromagnetic insulators KCoF3 and KNiF3 [1]\, in antiferromagnet
 ic metal FeRh [2]\, and rare earth-transition metal alloy CoGd [3]. Throug
 h our studies\, we are able to shed light on the microscopy of spin transf
 er at picosecond timescales and identify key figures of merit for its effi
 ciency.\n\n[1] Nature Communications 14\, 538 (2023)\n\n[2] Nature Communi
 cations 15\, 4958 (2024)\n\n[3] Advanced Optical Materials 2500056 (2025)\
 n\n \n\n2)The ambition of superconducting spintronics is to integrate mag
 netic and superconducting elements in a unique device that combines perman
 ent storage and low power logic characteristics. Recently\, new discoverie
 s have shown new routes for superconductivity and magnetism to co-operate\
 , enabling novel device concepts based on the interplay between spin\, cha
 rge and superconducting phase coherence. [1]. Understanding the timescales
  of this interplay is extremely important. For this reason\, the first que
 stion we are trying to answer is how fast a superconductor responds to a f
 ast perturbation\, such as spin or charge injection or a fast electric fie
 ld or magnetic field pulse. In this part of the talk I will discuss our ve
 ry recent experiments in which we apply THz time domain spectroscopy to st
 udy the dynamics of NbN superconducting thin films after pumping with a fe
 mtosecond IR pulse. Our measurements uncover a pronounced lengthening of t
 he superconductivity quenching time when the absorbed optical energy is cl
 ose to the condensation energy\, which constitutes a non-equilibrium analo
 gue of critical slowing down [2].\n\n[1] Nature Materials 17\, 499 (2018)\
 n\n[2] arXiv:2603.12473\n\nBio: Chiara Ciccarelli is Professor of Physics
  at the Cavendish Laboratory\, University of Cambridge. She completed her
  undergraduate and master studies at Tor Vergata University in Rome. After
  her PhD in Cambridge she held a Junior Research Fellowship at Gonville an
 d Caius College. In 2017 she started her research group at the Cavendish L
 aboratory with a Winton Advanced Research Fellowship. She is a Royal Socie
 ty University Research Fellow since October 2017. In 2023 she was nominate
 d Wohlfarth Lecturer by the Institute of Physics and has been awarded an E
 RC consolidator grant. 
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STATUS:CONFIRMED
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