BEGIN:VCALENDAR
VERSION:2.0
PRODID:-//Dirac Materials - ECPv4.9.6//NONSGML v1.0//EN
CALSCALE:GREGORIAN
METHOD:PUBLISH
X-WR-CALNAME:Dirac Materials
X-ORIGINAL-URL:http://diracmaterials.org
X-WR-CALDESC:Events for Dirac Materials
BEGIN:VTIMEZONE
TZID:"Europe/Stockholm"
BEGIN:DAYLIGHT
TZOFFSETFROM:+0100
TZOFFSETTO:+0200
TZNAME:CEST
DTSTART:20190331T010000
END:DAYLIGHT
BEGIN:STANDARD
TZOFFSETFROM:+0200
TZOFFSETTO:+0100
TZNAME:CET
DTSTART:20191027T010000
END:STANDARD
END:VTIMEZONE
BEGIN:VEVENT
DTSTART;TZID="Europe/Stockholm":20191107T140000
DTEND;TZID="Europe/Stockholm":20191107T150000
DTSTAMP:20260404T105416
CREATED:20191106T115507Z
LAST-MODIFIED:20191106T115507Z
UID:1584-1573135200-1573138800@diracmaterials.org
SUMMARY:Whiteboard discussion - Dirac Materials group & Xiao-Jia
DESCRIPTION:
URL:http://diracmaterials.org/calendar2/whiteboard-discussion-dirac-materials-group-xiao-jia/
CATEGORIES:Meeting
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID="Europe/Stockholm":20191107T150000
DTEND;TZID="Europe/Stockholm":20191107T160000
DTSTAMP:20260404T105416
CREATED:20191106T115721Z
LAST-MODIFIED:20191106T115721Z
UID:1586-1573138800-1573142400@diracmaterials.org
SUMMARY:[Colloqium] David Cassidy - Recent experimental progress in positronium-laser physics
DESCRIPTION:Speaker: David Cassidy from the University College London. \nTitle: Recent experimental progress in positronium-laser physics \nTime and place: Thursday November 7 at 15.15 (coffee and tea from 15.00) in the Oskar Klein auditorium FR4. \nAbstract:\nThe field of experimental positronium physics has advanced significantly in recent years\, in many cases by employing new techniques for trapping and manipulating positrons using Surko-type buffer gas traps [1]. These devices capture and store positrons\, allowing for the production of high quality DC beams\, or high intensity pulsed beams. The latter approach can be used to create an instantaneous cloud of Ps atoms that can be probed with standard ns pulsed lasers. This allows for the optical production of excited Ps states\, ranging from 2P levels\, which decay back to the ground state in 3.2 ns\, to metastable 2S states\, that cannot decay radiatively\, but will self-annihilate (in 1.1 microseconds)\, to long-lived Rydberg states\, that do not annihilate at all and\, for easily produced states\, may have radiative lifetimes of hundreds of microseconds [2]. The ability to generate Ps atoms in excited states facilitates numerous experimental programs [3]\, including precision optical and microwave spectroscopy and the application of Stark deceleration methods to guide\, decelerate and focus Rydberg Ps beams. In this talk I will discuss recent examples of such experiments and what may be possible in the near future. \nReferences\n[1] Plasma and trap-based techniques for science with positrons\, J. R. Danielson\, D. H. E. Dubin\, R. G. Greaves\, and C. M. Surko\, Rev. Mod. Phys. 87\, 247 (2015).\n[2] Measurement of Rydberg positronium fluorescence lifetimes\, A. Deller\, A. M. Alonso\, B. S. Cooper\, S. D. Hogan\, and D. B. Cassidy\, Phys. Rev. A 93\, 062513 (2016).\n[3] Experimental progress in positronium laser physics\, D. B. Cassidy\, Eur. Phys. J. D 72\, 53 (2018). \n
URL:http://diracmaterials.org/calendar2/colloqium-david-cassidy-recent-experimental-progress-in-positronium-laser-physics/
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID="Europe/Stockholm":20191107T161500
DTEND;TZID="Europe/Stockholm":20191107T164500
DTSTAMP:20260404T105416
CREATED:20191106T115210Z
LAST-MODIFIED:20191106T115210Z
UID:1580-1573143300-1573145100@diracmaterials.org
SUMMARY:Ren-Shu Wang - Exploring superconductivity in organobismuth molecules
DESCRIPTION:\nExploring superconductivity in organobismuth molecules\n \nRen-Shu Wang\nCenter for High Pressure Science and Technology Advanced Research\, Shanghai 201203\, China\n \nRecently\, novel quantum phenomena such as topological insulators and superconductors were suggested in organometallic materials. Three different types of organobismuth molecules\, including triphenylbismuth (TPB)\, tri-p-tolylbismthine (p-TTB)\, and tri-o-tolylbismthine (o-TTB)\, were investigated to explore organic superconductivity by alkali metal doping. The target organic molecules have similar structures\, expect for the type and the position of the functional group. The dc and ac magnetic susceptibility\, and electrical resistivity measurements reveal that all these doped molecules exhibit superconductivity\, and their Tc’s vary from 3.5 (and/or 7.2) to 3.6 (and/or 5.3) and 3.6 K for K-doped TPB\, p-TTB\, and o-TTB\, respectively. The shield fractions (SFs) of the main superconducting phases at 1.8 K are 3.74%\, 18%\, and 17% for K-doped TPB\, p-TTB\, and o-TTB\, respectively. In comparison with TPB\, adding the -CH3 groups in p-TTB and o-TTB do not make much difference for Tc of main phase rather than bringing about the increase of the SF\, indicating that the simple addition of functional groups is an effective way to tune (super)conductivity in such materials. The main superconducting phases and their composition in these molecules are determined by combined studies of X-ray diffraction and theoretical calculations as well as Raman spectroscopy measurements. These findings enrich the applications of organometallic compounds in superconductivity and add a new electron-acceptor family of organic superconductors. \n\n  \n\n\n  \n
URL:http://diracmaterials.org/calendar2/ren-shu-wang-exploring-superconductivity-in-organobismuth-molecules/
LOCATION:NORDITA // South  (Meeting Room 112.006B)\, Roslagstullsbacken 23\, Stockholm\, 106 91\, Sweden
CATEGORIES:Talks
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID="Europe/Stockholm":20191107T164500
DTEND;TZID="Europe/Stockholm":20191107T171500
DTSTAMP:20260404T105416
CREATED:20191106T115259Z
LAST-MODIFIED:20191106T115329Z
UID:1582-1573145100-1573146900@diracmaterials.org
SUMMARY:Di Peng - Antiferromagnetic order and possible quantum spin liquid in sodium doped 2\,2′-bipyridine  
DESCRIPTION:\nAntiferromagnetic order and possible quantum spin liquid in sodium doped 2\,2′-bipyridine\n \nDi Peng\nCenter for High Pressure Science and Technology Advanced Research\, Shanghai 201203\, China\n \nOrganic molecular solids with correlated electronics based on π-electron networks provide fertile ground for the search for peculiar materials\, including antiferromagnetic and quantum magnetism.  We report a development method for doping alkali metals into organic materials and forming a homogeneous phase together with the experimental discoveries of two antiferromagnetic phase in sodium doped 2\,2′-bipyridine at different molar ratios. An antiferromagnetic phase of 160 K is found in sodium-doped 2\,2′-bipyridine with a molar ratio of less than 1:1. Another antiferromagnetic phase with Neel temperature of 25 K is observed in samples with molar ratios of 1:1 and 1:2. Applying magnetic field can slowly suppress the 160 K antiferromagnetic phase\, while the 25 K antiferromagnetic phase is insensitive to the applied field rather than showing an increase of magnetization below 6 K. This behavior is consistent with the characteristics of quantum spin liquid\, in which strong quantum fluctuations lead to the disorder at low temperatures. We will discuss more about the experimental details about whether a strong spin frustrated antiferromagnetic phase is formed in sodium-doped 2\,2′-bipyridine and whether it enters a quantum spin liquid state at low temperatures.\n\n  \n
URL:http://diracmaterials.org/calendar2/di-peng-antiferromagnetic-order-and-possible-quantum-spin-liquid-in-sodium-doped-22%e2%80%b2-bipyridine/
CATEGORIES:Talks
END:VEVENT
END:VCALENDAR