ƒZƒ~ƒi[î•ñ

—ÊŒ¤EŒ´Žq—Í‹@\E•ºŒ§‘升“¯•¨«ƒRƒƒLƒEƒ€(‘æ105‰ñj
‹¤ÃF•ºŒÉŒ§—§‘åŠwƒtƒƒ“ƒeƒBƒA‹@”\•¨Ž¿‘n»ƒZƒ“ƒ^[EƒI[ƒvƒ“ƒZƒ~ƒi[i‘æ31‰ñj

The 105th QST-JAEA-UH Joint Condensed Matter Colloquium
The 31st Open Seminar of Resear Center for New Functional Materials

“úŽž: •½¬31”N1ŒŽ7“ú(ŒŽ) 16:15`17:15
Date and time: 7th Jan. (Mon.) 16:15 ` 17:15
êŠ: •ºŒÉŒ§—§‘åŠw—Šw•”Œ¤‹†“732ƒZƒ~ƒi[Žº
Place: Seminar room 732, Faculty of Science, University of Hyogo
‘è–¼: ‰ßŒXŽÎ‚µ‚½ƒfƒBƒ‰ƒbƒN“dŽqŒn‚Ìα-(BEDT-TTF)2I3‚Ì—˜_Œ¤‹†
Title: Theoretical study of α-(BEDT-TTF)2I3 with the over-tilted Dirac cones
u‰‰ŽÒ: ŠÝ–ØŒh‘¾iŒF–{‘åŠwj
Speaker: Prof. Keita Kishigi (Kumamoto University)
Abstract:

From the extended Hückel method for α-(BEDT-TTF)2I3 under the uniaxial pressure along y-axis, the Dirac cones are over-tilted till 2.3 kbar, where some theoretical results have been obtained[1-3].

We have found that the Dirac cones are critically tilted at 2.3kbar, where the dispersion is quadratic in one direction and linear in the other three directions[1]. We named this band crossing points and the Dirac cones as three-quarter Dirac points and the three-quarter Dirac cones. We have also shown the Landau levels by using the tight-binding model[1] and the 2×2 three-quarter Dirac Hamiltonian[2]. In ref [2], we have studied the Landau levels of the three-quarter Dirac cones in detail.

When the Dirac cones are over-tilted, the compensated metallic state is realized. Especially, above 0.2 kbar, the Fermi surface of two electron pockets are changed to one electron pocket, i.e., Lifshitz transitions[4] happen. We have quantum-mechanically calculated the de Haas van Alphen (dHvA) oscillations. Near the Lifshitz transitions, the Fourier components corresponding to the 3/2 and 5/2 areas of the hole pocket are enhanced[3]. It is not expected in the conventional Lifshitz and Kosevich formula[5] of the dHvA oscillations.

[1] Kishigi and Hasegawa, Phys. Rev. B 96, 085430 (2017).
[2] Hasegawa and Kishigi, arxiv1809.02276.
[3] Kishigi and Hasegawa, unpublished.
[4] Lifshitz, Sov.Phys. JETP 11, 1130 (1960).
[5] Lifshitz and Kosevich, Sov. Phys. JETP 2, 636 (1956).


¢˜bl: âˆä“O@i•ºŒÉŒ§—§‘åA—ÊŒ¤SPring-8j
“›ˆäŒ’“ñi—ÊŒ¤SPring-8j
’†–씎¶i•ºŒÉŒ§—§‘åj
Organizers: Toru Sakai(University of Hyogo, QST SPring-8)
Kenji Tsutsui(QST Pring-8)
Hiroki Nakano(University of Hyogo)