BEGIN:VCALENDAR VERSION:2.0 PRODID:IEEE vTools.Events//EN CALSCALE:GREGORIAN BEGIN:VTIMEZONE TZID:US/Mountain BEGIN:DAYLIGHT DTSTART:20190310T030000 TZOFFSETFROM:-0700 TZOFFSETTO:-0600 RRULE:FREQ=YEARLY;BYDAY=2SU;BYMONTH=3 TZNAME:MDT END:DAYLIGHT BEGIN:STANDARD DTSTART:20181104T010000 TZOFFSETFROM:-0600 TZOFFSETTO:-0700 RRULE:FREQ=YEARLY;BYDAY=1SU;BYMONTH=11 TZNAME:MST END:STANDARD END:VTIMEZONE BEGIN:VEVENT DTSTAMP:20191231T071503Z UID:5AD9EBE1-FAFF-48B5-8DDA-9FC91696AEC3 DTSTART;TZID=US/Mountain:20190222T110000 DTEND;TZID=US/Mountain:20190222T121500 DESCRIPTION:Though superconductors are revered for their ability to carry d issipation-free supercurrents below a material-dependent critical current (Jc)\, the seemingly inconspicuous action of vortices can introduce dissip ation even for currents well below Jc. In type II superconductors (includi ng high-Tc cuprates\, iron-based superconductors\, and MgB2) immersed in h igh enough magnetic fields\, vortices are formed by the penetration of mag netic flux and can be moved by current-induced forces and thermal energy. Vortex motion can be disruptive: it limits the current-carrying capacity i n wires\, can cause losses in microwave circuits\, and\, more generally\, can induce phase transitions. Understanding vortex dynamics is a formidabl e challenge because of the complex interplay between moving vortices\, mat erial disorder (defining pinning sites) that can counteract vortex motion\ , and thermal energy that can cause vortices to escape from these pinning sites. In particular\, we cannot precisely predict the rate of thermally a ctivated vortex motion (creep) in a given sample\, and tuning the creep ra te by modifying the microstructure is typically achieved by means of trial and error. Furthermore\, common techniques to enhance Jc by adjusting the disorder landscape (e.g.\, irradiation or incorporation of non-supercondu cting inclusions) are often accompanied by unfavorable increases in the cr eep rate.\n\nIn this talk\, I will discuss the importance of minimizing cr eep and my efforts to better understand vortex creep. I will cover results from studies of a wide variety of materials. Additionally\, I will presen t our proposal of the existence of a universal minimum realizable creep ra te that depends on material parameters. This limitation is of both fundame ntal and technological significance: it provides new clues about the inter play between material parameters and vortex dynamics and about how to engi neer materials with slow creep. This hard constraint\, applicable at low t emperatures and fields\, has two important implications: first\, the creep problem in high-Tc superconductors cannot be fully eliminated and there i s a limit to how much it can be ameliorated\; and second\, we can predict that any yet-to-be-discovered high-Tc superconductors will have fast creep .\n\nCo-sponsored by: UCCS\n\nSpeaker(s): Serena Eley\, \n\nRoom: A204\, B ldg: Osborne\, 1420 Austin Bluffs Parkway\, Colorado Springs\, Colorado\, United States\, 80918 LOCATION:Room: A204\, Bldg: Osborne\, 1420 Austin Bluffs Parkway\, Colorado Springs\, Colorado\, United States\, 80918 ORGANIZER:zcelinsk@uccs.edu SEQUENCE:0 SUMMARY:Resistance is Not Futile: Pinning Down Elusive Vortices in Supercon ductors URL;VALUE=URI:https://events.vtools.ieee.org/m/216658 X-ALT-DESC:Description: <br /><p>Though superconductors are revered for the ir ability to carry dissipation-free supercurrents below a material-depend ent critical current (<em>J</em><sub>c</sub>)\, the seemingly inconspicuou s action of vortices can introduce dissipation even for currents well belo w <em>J</em><sub>c</sub>. In type II superconductors (including high-<em>T </em><sub>c</sub> cuprates\, iron-based superconductors\, and MgB<sub>2</s ub>) immersed in high enough magnetic fields\, vortices are formed by the penetration of magnetic flux and can be moved by current-induced forces an d thermal energy. Vortex motion can be disruptive: it limits the current-c arrying capacity in wires\, can cause losses in microwave circuits\, and\, more generally\, can induce phase transitions. Understanding vortex dynam ics is a formidable challenge because of the complex interplay between mov ing vortices\, material disorder (defining pinning sites) that can counter act vortex motion\, and thermal energy that can cause vortices to escape f rom these pinning sites.&nbsp\; In particular\, we cannot precisely predic t the rate of thermally activated vortex motion (creep) in a given sample\ , and tuning the creep rate by modifying the microstructure is typically a chieved by means of trial and error.&nbsp\; Furthermore\, common technique s to enhance <em>J</em><sub>c</sub> by adjusting the disorder landscape (e .g.\, irradiation or incorporation of non-superconducting inclusions) are often accompanied by unfavorable increases in the creep rate.&nbsp\;</p>\n <p>In this talk\, I will discuss the importance of minimizing creep and my efforts to better understand vortex creep. I will cover results from stud ies of a wide variety of materials.&nbsp\;&nbsp\; Additionally\, I will pr esent our proposal of the existence of a universal minimum realizable cree p rate that depends on material parameters. This limitation is of both fun damental and technological significance: it provides new clues about the i nterplay between material parameters and vortex dynamics and about how to engineer materials with slow creep. This hard constraint\, applicable at l ow temperatures and fields\, has two important implications: first\, the c reep problem in high-<em>T</em><sub>c</sub> superconductors cannot be full y eliminated and there is a limit to how much it can be ameliorated\; and second\, we can predict that any yet-to-be-discovered high-<em>T</em><sub> c</sub> superconductors will have fast creep.</p> END:VEVENT END:VCALENDAR