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X-WR-CALNAME:Theoretical Quantum Matter
X-ORIGINAL-URL:https://tqmatter.org
X-WR-CALDESC:Events for Theoretical Quantum Matter
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TZID:Europe/Stockholm
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BEGIN:VEVENT
DTSTART;TZID=Europe/Stockholm:20190903T110000
DTEND;TZID=Europe/Stockholm:20190903T120000
DTSTAMP:20260501T180913
CREATED:20190903T081516Z
LAST-MODIFIED:20190903T081516Z
UID:1240-1567508400-1567512000@tqmatter.org
SUMMARY:[CMT SEMINAR] Ipsita Mandal - Some aspects of correlated electrons
DESCRIPTION:Speaker: Ipsita Mandal \n\nAffiliation: University of Stavanger\,\n\n\nTitle: Some aspects of correlated electrons\,\n \nTime:  Fika 10:30-11:00 \, Seminar 11:00-12:00\,\nPlace: Nordita South\, room 112:028 .\n\nAbstract:\nIn this talk\, I am going to present exciting results from two of my ongoing/recent projects.\nFirst part:\nSpin-orbit coupling (SOC) assisted (spin j = 1/2) Mott insulators exhibiting bond-directional exchange interactions are expected to exhibit unconventional quantum magnetic phases like spin liquids [1\, 2] predicted by the Kitaev model\, dubbed as Kitaev spin liquid (KSL). The feature of a Kitaev material is that the Kitaev coupling is the dominant exchange coupling. Compounds like honeycomb iridates and α-RuCl_3 have been identified as candidate Kitaev materials. In the first part of my talk\, I will address the unresolved question whether α-RuCl_3 is actually a Kitaev material. If yes\, what is the value of the Kitaev coupling strength? If not\, what are the dominant terms in the effective spin Hamiltonian that can describe the system? We focus on the results from resonant torsion magnetometry experiments by Modic et al\, which they can measured the magnetotropic coefficient k\, when a magnetic field B is applied making angle θ with the c-axis of the crystal. Using a simple Hamiltonian with a dominant paramagnetic term\, we will show that we can fit the data obtained in the experiments.\n \nSecond part:\nIn sufficiently clean metals\, it is possible for electrons to collectively flow as a viscous fluid at finite temperature. These viscous effects have been predicted to give a notable magneto resistance\, but whether the magnetoresistance is positive or negative has been debated. We argue that regardless of the strength of inhomogeneity\, bulk magnetoresistance is always positive in the hydrodynamic regime.\n 
URL:https://tqmatter.org/event/cmt-seminar/
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BEGIN:VEVENT
DTSTART;TZID=Europe/Stockholm:20190903T100000
DTEND;TZID=Europe/Stockholm:20190903T110000
DTSTAMP:20260501T180913
CREATED:20190830T142740Z
LAST-MODIFIED:20190830T142740Z
UID:1233-1567504800-1567508400@tqmatter.org
SUMMARY:[Talk] Shota Kanasugi - Spin-orbit-coupled ferroelectric superconductivityand multiorbital effects in SrTiO3
DESCRIPTION:Speaker: Shota Kanasugi\nAffiliation: Kyoto University \nTitle: Spin-orbit-coupled ferroelectric superconductivityand multiorbital effects in SrTiO3 \nAbstract: A lot of exotic superconducting statesemerge close to other ordered phases\, such as anisotropic superconductivity in cuprates. Although previous studies have mainly focused on the superconductivityclose to magnetic instability\, the ferroelectric (FE) counterpart is recently receiving increased attention since such superconductivity was reported in doped SrTiO3(STO). STO is a unique compound which exhibits both quantum paraelectricity and superconductivity. The superconducting transition temperature is enhanced in the vicinity of the FE quantum critical point [1-4]. Moreover\, recent experiments suggest the coexistence ofsuperconductivity and ferroelectricity in doped STO [2]. These results imply a cooperative correlation between superconductivity and ferroelectricity against a long-held belief that they should be incompatible.In this talk\, we present that aFE-like polar inversion symmetry breaking order can be controlled by the superconductivityin spin-orbit coupled systems. We introduce a model of electron-lattice coupled two-dimensional superconductor\,in which the ferroelectricity-induced Rashba spin-orbit coupling [5]is included. It is shown that the FE superconductivity\,which is characterized by a FE structural transition in the superconducting state\,is realized through two different mechanisms [6]. First\, the FE superconducting state is stabilized by the Lifshitz transition of the Rashba split bandsin lowcarrier density regimes.Second\, the FE superconductingstate is stabilized under a Zeeman magnetic field\, thanksto the suppressionof the Pauli depairingeffect in the FE phase. Furthermore\, we show that the FE superconductivity in bulk STO is strongly affected by the multiorbital effectoft2gelectrons[7]. Then\, we predict a topologicalWeyl superconducting state in the FE superconducting phase of bulk STO. \nReferences\n[1] A. Stucky et al.\, Sci. Rep. 6\,37582 (2016).\n[2] C. W. Rischau et al.\, Nat. Phys. 13\, 643 (2017).\n[3] Y. Tomioka et al.\, Nat. Commun. 10\, 738 (2019).\n[4] K. Ahadi et al.\, Sci. Adv. 5\, eaaw0120 (2019).\n[5] G. Khalsa\, B. Lee\, and A. H. MacDonald\, Phys. Rev. B 88\, 041302 (2013).\n[6] S. Kanasugi and Y. Yanase\, Phys. Rev. B 98\, 024521 (2018).\n[7] S. Kanasugi and Y. Yanase\, arXiv: 1904.11113 (2019)
URL:https://tqmatter.org/event/talk-shota-kanasugi-spin-orbit-coupled-ferroelectric-superconductivityand-multiorbital-effects-in-srtio3/
LOCATION:NORDITA // South  (Meeting Room 112.006B)\, Roslagstullsbacken 23\, Stockholm\, 106 91\, Sweden
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BEGIN:VEVENT
DTSTART;VALUE=DATE:20190902
DTEND;VALUE=DATE:20190903
DTSTAMP:20260501T180913
CREATED:20190830T141617Z
LAST-MODIFIED:20190830T141617Z
UID:1230-1567382400-1567468799@tqmatter.org
SUMMARY:Odd-Frequency Meeting in Uppsala
DESCRIPTION:
URL:https://tqmatter.org/event/odd-frequency-meeting-in-uppsala/
LOCATION:Uppsala University\, Uppsala\, Sweden
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BEGIN:VEVENT
DTSTART;TZID=Europe/Stockholm:20190830T080000
DTEND;TZID=Europe/Stockholm:20190830T170000
DTSTAMP:20260501T180913
CREATED:20190830T141515Z
LAST-MODIFIED:20190830T141515Z
UID:1228-1567152000-1567184400@tqmatter.org
SUMMARY:Seminar - Markus Müller (PSI)
DESCRIPTION:Speaker: Markus Müller\nAffiliation: Paul Scherrer Institut (PSI) in Switzerland\n\n\nTitle: Coherent oscillators\, spectral hole-burning and emerging q-bits in rare earth magnets\n\n\n \nAbstract: Experiments in rare earth compounds\, such as LiHoYF4 and GGG (Gd-Ga-garnet)\, have demonstrated very long lived\, coherent quantum degrees of freedom with sharply defined excitation energies\, many orders of magnitude below the scale of typical magnetic interactions (exchange\, dipolar or hyperfine interactions)\, and with life times on the order of seconds.\nThe nature of these coherent entities in the midst of a solid state environment has remained a mystery for a long time. I will discuss their likely origin and argue that they arise from an intricate interplay between several nuclear and electronic spins\, and exist only in long lived states out of equilibrium. The sharpness of the excitations is protected by Anderson localization of composite objects\, with an unusual type of power law hopping. The emerging\, well isolated degrees of freedom may be promising candidates for magnetic qubits.\nTime permitting I will discuss ideas of how to realise quantum memories and gates based on electro-nuclear qubits in rare earth systems.\n\n 
URL:https://tqmatter.org/event/seminar-markus-muller-psi/
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BEGIN:VEVENT
DTSTART;TZID=Europe/Stockholm:20190212T150000
DTEND;TZID=Europe/Stockholm:20190212T161500
DTSTAMP:20260501T180913
CREATED:20190205T194233Z
LAST-MODIFIED:20190205T194233Z
UID:839-1549983600-1549988100@tqmatter.org
SUMMARY:Group Meeting
DESCRIPTION:Presentation by Valera Kozin\, a visiting PhD student (profile here)\n\nTitle: “Multiply-connected nanostructures in the regime of strong light-matter coupling. Self-organizing maps as a method for detecting phase transitions”. \nAbstract:\nIt is demonstrated that the dressing field drastically modifies all electronic characteristics of the quantum rings\, including spin-orbit coupling\, effective electron mass\, and optical response. \nThe Chern insulator phase is shown to emerge in two-dimensional arrays of polariton rings where the time-reversal symmetry is broken due to the application of an out-of-plane magnetic field. \nWe employ a specific unsupervised machine learning technique—self-organizing maps—to create a low-dimensional representation of microscopic states\, relevant for macroscopic phase identification and detecting phase transitions. We explore the properties of spin Hamiltonians of two archetype model systems: a two-dimensional Heisenberg ferromagnet and a three-dimensional crystal\, Fe in the body-centered-cubic structure. The method of self-organizing maps\, which is known to conserve connectivity of the initial dataset\, is compared to the cumulant method theory and is shown to be as accurate while being computationally more efficient in determining a phase transition temperature. \n\nSlot for APS March Meeting still available.  Contact David for booking.
URL:https://tqmatter.org/event/group-meeting-2/
LOCATION:NORDITA // South  (Meeting Room 112.006B)\, Roslagstullsbacken 23\, Stockholm\, 106 91\, Sweden
CATEGORIES:Group Meetings
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BEGIN:VEVENT
DTSTART;TZID=Europe/Stockholm:20190205T150000
DTEND;TZID=Europe/Stockholm:20190205T161500
DTSTAMP:20260501T180913
CREATED:20190205T193544Z
LAST-MODIFIED:20190205T193544Z
UID:836-1549378800-1549383300@tqmatter.org
SUMMARY:Group Meeting
DESCRIPTION:
URL:https://tqmatter.org/event/group-meeting/
LOCATION:NORDITA // South  (Meeting Room 112.006B)\, Roslagstullsbacken 23\, Stockholm\, 106 91\, Sweden
CATEGORIES:Group Meetings
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