DQMP Forum - Daniel G. Suarez-Forero - Giulia Venditti

17.12.2024 13:00 – 14:00

Giant Enhancement of Exciton Diffusion near an Electronic Mott Insulator
Daniel G. Suarez-Forero, group of prof. Srivastava

Bose-Fermi mixtures naturally appear in various physical systems. In semiconductor heterostruc-tures, such mixtures can be realized, with bosons as excitons and fermions as dopant charges [1]. How-ever, the complexity of these hybrid systems chal-lenges the comprehension of the mechanisms that determine physical properties such as mobility. In this study, we investigate interlayer exciton diffusion in an H-stacked WSe2/WS2 heterobilayer [2]. Our measurements are performed in the dilute exciton density limit at low temperatures to examine how the presence of charges affects exciton mobility. Re-markably, for charge doping near the Mott insulator phase, we observe a giant enhancement of exciton diffusion of three orders of magnitude compared to charge neutrality. We attribute this observation to mobile valence holes, which experience a suppressed moir´e potential due to the electronic charge order in the conduction band, and recombine with any conduction electron in a non-monogamous manner. This new mechanism emerges for sufficiently large fillings in the vicinity of correlated generalized Wigner crystal and Mott insulating states. Our results demonstrate the potential to characterize correlated electron states through exciton diffusion and provide insights into the rich interplay of bosons and fermions in semiconductor heterostructures.

[1] Gao et al., Nat Comm 15, 2305 (2024).
[2] Upadhyay et al., arXiv:2409.18357 (2024)


Challenges, Stability, and (A)symmetries in Vortex-core Majorana Zero Modes
Giulia Venditti, group of prof. Rademaker

The search for Majorana particles (MP) is crucial both for fundamental physics and potential topo-logical quantum computation. Being an equal su-perposition of particle and antiparticle, MP are nat-urally sought in superconductors as Majorana zero modes (MZMs). Fu and Kane showed [1] that a MZM can emerge in the vortex-core states of an s-wave superconductor on top of a strong topological insulator (TI). It would be then natural to propose that high-temperature cuprates would enhance the MZMs protection [2]. However, when considering vortices inside a d+id-wave superconductor on top of a TI, the stability of MZMs is limited by an effec-tively much smaller gap than the size of the order parameter suggests [3]. Our numerical simulations reveal an asymmetry in the appearance of MZMs between vortices and antivortices. When combined, MZMs can vanish.
In this talk, I will discuss the stability of Majorana zero modes arising from vortex core states in topological superconductors.

[1]Liang Fu, and C. L. Kane, Phys. Rev. Lett. 100, 096407 (2008).
[2]A. Mercado, S. Sahoo, and M. Franz, Phys. Rev. Lett. 128, 137002 (2022).
[3]C. Berthod, G. Venditti, L. Rademaker, In preparation.

Lieu

Bâtiment: Ecole de Physique

Auditoire Stückelberg

entrée libre