Dresden 2020 – wissenschaftliches Programm

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CPP: Fachverband Chemische Physik und Polymerphysik

CPP 17: 2D Materials I: Electronic Structure, Excitations, etc. (joint session O/CPP/HL)

CPP 17.6: Vortrag

Montag, 16. März 2020, 12:00–12:15, WIL C107

Melting the low temperature gap in monolayer VSe2, in time resolved ARPES — •Deepnarayan Biswas1,2, Alfred Jones1, Paulina Majchrzak1,3, Klara Volckaert1, Charlotte Sanders1,3, Igor Marković2, Federico Andreatta1, Akhil Rajan2, Yu Zhang3, Gabriel Karras3, Tsung-Han Lee4, Chang-Jong Kang4, Byoung Ki Choi5, Richard Chapman3, Adam Waytt3, Emma Springate3, Jill Miwa1, Philip Hofmann1, Phil D. C. King2, Young Jun Chang5, Nikola Lanata1, and Søren Ulstrup11Aarhus University, Denmark — 2University of St Andrews, UK — 3Central Laser Facility, UK — 4Rutgers University, USA — 5University of Seoul, Republic of Korea

The group V transition metal dichalcogenide VSe2 shows a charge density wave (CDW) transition at 110 K with (4×4×3) charge ordering in its bulk form. In contrast, recent experiments on monolayer (ML) VSe2 have shown an enhanced transition at ∼ 140 K with very different charge ordering. Moreover, this transition is accompanied by a full gapping of the Fermi surface. Here, we have used time and angle resolved photoelectron spectroscopy (TR-ARPES) to understand the electron dynamics in ML VSe2 above and below the transition temperature. We have also modelled the ARPES intensity using a modified BCS self energy and density functional theory calculated bare bands. We find the gapped phase vanishes upon pumping and takes unusually long time to recover (more than 10 ps). This behaviour points toward a hot electron relaxation bottleneck coupled with an electronic phase transition in this sample.

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