2D quantum states with tunable interactions

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Quantum optoelectronics

Quantum engineering

Optothermics

2D ordering phenomena

Quantum optoelectronics

The variety of available low-dimensional systems gives access to a wealth of electronic properties, among which direct bandgap allows for optoelectronic applications. Interestingly, all low-dimensional materials we investigate exhibit optical phonons that couple to electrons and can be probed with Raman spectroscopy.

We investigate interlayer and intralayer excitons, free carriers in low-dimensional materials in a transistor configuration, excitonic interactions, defects as photon sources [1,2]. Photoluminescence and Raman spectroscopy along with electronic transport provide insights into the electronic structure and transitions at play in heterostructures. In addition, we take advantage of the possible functionalization of low-dimensional systems via pi-stacked molecules to explore phenomena such as charge or energy transfer as well as light-activated tunneling [3].

[1] S. Dubey et al., ACS Nano 11, 11206 (2017)

[2] G. Nayak et al., Phys. Rev. Materials 11, 114001 (2019)

[3] Y. Chen et al., Advanced Materials 31, 1902917 (2019).

Contact : laetitia.marty@neel.cnrs.fr

Quantum engineering

We couple two dimensional materials to confined electromagnetic fields in order to study interacting quantum systems in different regimes.

In superconducting circuits, working with microwave photons, we integrate graphene electronic transport channels and exploit their unique gate tunability. More specifically, we have recently demonstrated a gate tunable Josephson parametric amplifier that operates at the quantum limit [1]. The tunability of graphene Josephson junctions is also promising for the gate tunable superconducting Qubits we are currently developing.

In the optical domain, we integrate 2D transition metal dichalcogenides (TMDC) within microcavities. We focus on the interaction between optical excitations (i.e. excitons), which is peculiar in TMDCs, in order to demonstrate non-classical sources of photons [2].

[1] G. Butseraen et al., Nat. Nanotechnol. 17, 1147 (2022)

[2] P. Stepanov et al., Phys. Rev. Lett. 126, 167401 (2021)

Contact: julien.renard@neel.cnrs.fr

A monolayer transition metal dichalcogenides inserted in an optical microcavity

A graphene based Josephson junction can be inserted in a microwave cavity to allow gate tunability

Optothermics

One-atom thick membranes, which are surfaces with no bulk exhibit unusual thermal and mechanical properties. In particular, graphene exhibits very high thermal conductivity and thermal regimes not fully elucidated yet.

We use optical techniques, in particular Raman spectroscopy, for thermal measurements of 2D membranes. We recently implemented a two-laser approach using one laser as the heater and the other as the local temperature probe. This allows imaging the spatial temperature distribution and thereby directly determining heat fluxes, which we analyse with models beyond the Fourier law [1]. This opens new perspectives on thermal transport at the nanoscale.

[1] P. Singh et al., PhD manuscript, UGA (2022)

Contact: nedjma.bendiab@univ-grenoble-alpes.fr

2D ordering phenomena

In two-dimensional systems, a multitude of commensurate and incommensurate phases, topological phase transitions, highly degenerate ground states, etc, can occur. We explore such phases related to structural (e.g. moiré patterns), spin (e.g. magnetically-ordered phases) and charge (e.g. charge density waves, superconducting states) degrees of freedom, in presence of classical and quantum kinds of interactions.

We investigate these (dis)order phenomena in epitaxial two-dimensional systems (graphene, transition metal dichalcogenides) forming various kinds of commensurate and incommensurate super-orders ; and in exfoliated metallic transition metal dichalcogenides, some of which are prone to electronic instabilities mediated by interactions with phonons (TaS₂, TaSe₂) and others to magnetic ordering up to room temperature (CrTe₂). Thickness-dependent order/disorder is probed at the atomic scale with scanning tunneling microscopy, with high-resolution synchrotron X-ray diffraction, and with the help of optical probes, Raman spectroscopy and magneto-optical Kerr effect magnetometry at variable temperatures and with spatial resolution.

[1] A. Purbawati, S. Sarkar et al. ACS Appl. Elec. Mater. ASAP article

[2] S. Layek et al.,. Carbon, 201, 667 (2023).

[3] S. Lisi et al. Phys. Rev. Lett. 129, 096101 (2022)

[4] A. Purbawati et al. ACS Appl. Mater. Interf. 12, 30702 (2020) 

Contact: johann.coraux@neel.cnrs.fr

2D Fab

Van der Waals heterostructures, tailor-made crystals obtained by stacking 2D materials, open a wide range of new functions in condensed matter. Fine tuning of the different interactions at play in 2D heterostructures is achieved with the use of few layer graphene electrostatic gates, with the controlled mismatch angle between layers and other nanofabrication techniques compatible with 2D materials.

The 2Dfab platform is operated in collaboration with the QNES team, and with support from the Nanofab and Experimental Engineering technical groups of the lab. It gathers state-of-the-art, in-house-developed manipulation tools including micro-transfer stages for dry stamping 2D materials one of which is operated within our Ar glove-box. Further processing can be performed like annealing, or surface treatments in a clean chemistry room, while device fabrication is performed at the Nanofab facility.

[1] D. Dufeu, et al., Highlights – Institut Néel, 20 (2016).

[2] L. Marty, et al., Nanosciences Fondation Graphene Highlights, 25 (2013).