PhD defense by Ana Elena Tutueanu
Magnetic structure and dynamics of cuprate superconductors
studied by neutron scattering
Solving the long-standing question of the origin of high temperature superconductivity will undoubtedly be one of the most celebrated achievements of, hopefully, this century. The discovery will not only be exceptional in itself but also through the remarkable amount of research that will lead up to it. Still today, high temperature superconductivity remains one of the most active research fields thanks to improved experimental techniques and sample preparation methods as well as theoretical and modelling advances.
In the cuprates family of high temperature superconductors, there is ample evidence supporting the idea that the complex magnetism, exhibited by these materials, is strongly connected to superconductivity. For this reason we have decided to study the interplay between these two by means of elastic and inelastic neutron scattering. To address this issue we have focused on a very specific region of the phase diagram of the archetypal cuprate La2-x SrxCuO4. These samples exhibit a zero-temperature phase transition between an insulating and a superconducting phase around strontium doping 𝑥 = 0.055. The consistent study of crystals with different levels of strontium doping around this transition point has revealed a number of similarities and differences between superconducting and non-superconducting samples. To account for the observed behaviours of these samples under different applied magnetic field and temperature conditions we propose a model composed of several coexisting electronic orders. We argue that the phase diagram of LSCO displays coexisting pair density wave and uniform d–wave superconducting regions, the ratio of which can be tuned by adjusting the doping concentration.
An essential aspect in developing a unified theory to explain high temperature superconductivity is the universality of the observed traits across all the compounds of this class of materials. One of the most interesting and challenging compounds to test is the oxygen doped La2CuO4+y. Even though crystallographically it is very similar to the other constituents of the family the mobility of the doped ions gives rise to new intriguing phenomena. Part of this research work has been dedicated to performing a detailed study of this sample. Elastic and inelastic neutron scattering have been used to analyse the magnetic field and temperature dependence of both static and dynamic spin stripes. Polarisation analysis was also employed in order to determine the orientation of the two signals.
- Zoom Meeting: https://ucph-ku.zoom.us/j/64254206566
- Meeting ID: 642 5420 6566
Brian Møller Andersen is inviting you to a scheduled Zoom meeting. Topic: Ana-Elena Tutueanu PhD defenseTime: May 12, 2021 01:30 PM CopenhagenJoin Zoom Meeting https://ucph-ku.zoom.us/j/64254206566 Meeting ID: 642 5420 6566 One tap mobile+4589883788,,64254206566# Denmark+4532701206,,64254206566# Denmark Dial by your location +45 89 88 37 88 Denmark +45 32 70 12 06 Denmark +45 32 71 31 57 Denmark +39 069 480 6488 Italy +39 020 066 7245 Italy +39 021 241 28 823 Italy +33 1 8699 5831 France +33 1 7037 2246 France +33 1 7037 9729 France +49 69 7104 9922 Germany +49 30 5679 5800 Germany +49 695 050 2596 Germany +44 203 481 5240 United Kingdom +44 131 460 1196 United Kingdom +44 203 481 5237 United Kingdom +1 470 381 2552 US (Atlanta) +1 602 753 0140 US (Phoenix) +1 646 518 9805 US (New York) +1 646 558 8656 US (New York) +1 651 372 8299 US (Minnesota) +1 669 219 2599 US (San Jose) +1 720 707 2699 US (Denver) +1 720 928 9299 US (Denver) +1 786 635 1003 US (Miami) +1 971 247 1195 US (Portland) +1 213 338 8477 US (Los Angeles) +1 253 215 8782 US (Tacoma) +1 267 831 0333 US (Philadelphia) +1 301 715 8592 US (Washington DC) +1 312 626 6799 US (Chicago) +1 346 248 7799 US (Houston) +1 408 652 8184 US (San Jose) +1 470 250 9358 US (Atlanta)Meeting ID: 642 5420 6566Find your local number: https://ucph-ku.zoom.us/u/cAxViW0VF Join by SIP64254206566@109.105.112.23664254206566@109.105.112.235 Join by H.323109.105.112.236109.105.112.235Meeting ID: 642 5420 6566