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SUMMARY:Multiplexer on the 0.7 anomaly in quantum point contacts (SP Works
 hop) - Mr Pengcheng Ma (University of Cambridge\, Semiconductor Physics Gr
 oup)
DTSTART:20170308T141500Z
DTEND:20170308T151500Z
UID:TALK68989@talks.cam.ac.uk
CONTACT:Teri Bartlett
DESCRIPTION:The ‘0.7 anomaly’ refers to an unexpected shoulder at ~0.7
 *(2e2/h) in the linear conductance of a quantum point contact (QPC) [1]\, 
 which occurs as a result of electron-electron (e-e) interactions.  However
 \, its origin is still under debate over twenty years.  We measured thousa
 nds of QPC devices using a multiplexer statistic technique [2-3] and try t
 o experimentally verify a recent van Hove scenario theory [4] that governs
  the 0.7 anomaly\, compared with the phenomenological model of spontaneous
  spin polarization. \nVG Dependence: By sweeping the split-gate voltage (V
 G)\, the 0.7 anomaly forms at the maximum of the van Hove ridge-like local
  density of states (LDOS)\, which amplifies the e-e interactions to be str
 ongest and thus make the suppression of conductance largest. \nEx Dependen
 ce: Decreasing the curvature of the longitudinal potential barrier (Ex) ha
 s qualitatively similar effects compared with increasing e-e interaction s
 trength\, in that both can cause the 0.7 anomaly more prominent.\nB Depend
 ence: In low parallel field\, the magnetoconductance depends quadratically
  on the field in the sub-open regime. This Fermi-liquid property links the
  magnetoresponse strength to the local spin susceptibility fluctuations\, 
 which is largest also at the maximum of LDOS. \n\nReference:\n\n[1] K. J. 
 Thomas et al Phys. Rev. Lett. 77\, 135 (1996)\n[2] H. Al-Taie et al App. P
 hys. Lett. 102\, 243102 (2013)\n[3] L. W. Smith et al Phys. Rev. Applied 5
 \, 044015 (2016)\n[4] F. Bauer et al Nature 501\, 73 (2013).\n
LOCATION:Mott Seminar Room (Mott Building Room 531)\, Cavendish Laboratory
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