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DTSTAMP:20260424T040959Z
UID:1683018000@ist.ac.at
DTSTART:20230502T110000
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DESCRIPTION:Speaker: Maosen Qin\nhosted by Hryhoriy Polshyn\nAbstract: The 
 semiconducting monolayer transition metal dichalcogenides (MoS2\, WSe2\, W
 S2\, etc.) (TMDCs) have attracted great interest due to their large direct
  band-gap\, Berry phase-related physical properties\, and strong spin-orbi
 t coupling that leads to spin-valley locking. Although they are well studi
 ed by optical means\, the study of transport properties is still lacking b
 ecause of the difficulties in achieving Ohmic contact. In my talk\, I will
  focus on the transport properties of the semiconducting monolayer TMDCs\,
  which are detected by ionic liquid gating technique. Taking advantage of 
 the broad doping capability\, we can access the whole electronic phase dia
 gram of monolayer WSe2 and observe a cascade of phases “band insulator-
 superconductor-emergent insulator-quasi metal” as the doping level incre
 ases. We find that the emergent insulator is derived from a split narrow s
 ubband\, the half-filling of which corresponds to the insulating dome peak
 . This correlation picture is supported by a charge density wave that poss
 esses an isolated flat band. Then I will introduce a new optical stimulus 
 that enables the ionic liquid gating transistor to operate at cryogenic te
 mperature and discuss the underlying mechanism. Finally\, I will present t
 he realization of the nonlinear Hall effect under time-reversal-symmetric 
 conditions in the strained monolayer WSe2. Our observation indicates that 
 the C3v symmetry of monolayer WSe2 is broken by the strain and the finit
 e Berry curvature dipole emerges. Therefore\, upon applying an electric fi
 eld E\, the Berry curvature dipole D can lead to an out-of-plane orbita
 l magnetization M∝D·E\, which further induces this novel second-harmon
 ic Hall effect. Remarkably\, the magnitude of the nonlinear Hall signals c
 an be effectively tuned by the strain\, which is very promising for practi
 cal applications.
LOCATION:Foyer seminar room Ground floor / Office Bldg West\, ISTA
ORGANIZER:
SUMMARY:Maosen Qin: Electronic phase diagram and nonlinear Hall effect in i
 onic liquid gated monolayer transition metal dichalcogenides semiconductor
URL:https://talks-calendar.ista.ac.at/events/4134
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