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SUMMARY:Seminar on Superconductivity enhancement in polar metals  -  Isao 
 H. Inoue from National Institute of Advanced Industrial Science and Techno
 logy (AIST)\, Tsukuba\, Japan
DTSTART:20231101T141500Z
DTEND:20231101T153000Z
UID:TALK207829@talks.cam.ac.uk
CONTACT:Siddharth Saxena (Montu)
DESCRIPTION:Abstract\nSubstitution of Nb5+ for Ti4+ in SrTiO3 (denoted as 
 Nb:SrTiO3) is an excellentelectron doping\nmethod with reduceddisorder\, s
 uperior mobility\,and higher Tc\, comparedwith the electrondoping\nby crea
 tingthe oxygen defectsdenoted as SrTiO3-δ. We applied the Nb doping to th
 e two\ndifferentferroelectric materials\, Sr0.95Ba0.05TiO3 and Sr0.985Ca0.
 015TiO3\, confirmed\, by the xray structural analyses\, they turned into p
 olar metals with broken centrosymmetry. We can define\na particular carrie
 r density n* for the polar metals. When the carrier density n < n*\, the r
 esistance\nshows an upturn below the temperature TK. The values of TK incr
 ease monotonically as the\ncarrier density decreases. Interestingly\, they
  coincide with the ferroelectric Curie temperature at\nthe zero carrier de
 nsity limit. Although the values of n* for Nb:Sr0.985Ca0.015TiO3 and\nNb:S
 r0.95Ba0.05TiO3 are different by one order of magnitude\, both materials s
 how typical\nsuperconducting domes with single peaks commonly located arou
 nd 1020 cm−3. Compared with\nthe nonpolar matrix Nb:SrTiO3\, the values 
 of Tc are enhanced and reach 0.75 K for\nNb:Sr0.95Ba0.05TiO3. However\, th
 e Tc enhancement was insignificant (less than 0.1 K) at\naround n*. The en
 hancement becomes much more prominent further inside the dilute carrierden
 sity region\, where the screening is less effective. These results suggest
  that centrosymmetry\nbreaking\, i.e.\, the ferroelectric nature\, does no
 t kill the superconductivity. Instead\, it enhances the\nsuperconductivity
  directly\, despite the absence of strong quantum fluctuations. Our result
 s call for\na reconsideration of the existing microscopic models of superc
 onductivity in SrTiO3.\n*This study was supported by JSPS KAKENHI (19H0184
 4 and 18H03686) and was\npartially supported by the JST CREST (JPMJCR19K2)
 .
LOCATION:Mott Seminar Room (531)\, Cavendish Laboratory\, Department of Ph
 ysics
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