Saber ROSTAMZADEH

Techniques de recherche

I am a Marie Curie Fellow working at the intersection of cavity quantum electrodynamics — exploring the quantum nature of light — and quantum transport, which probes measurable electronic conduction at the nonscales where quantum effects dominate. Inside an optical cavity, charge carriers hybridize with the confined light field — even without illumination, via vacuum fluctuations — and the transport channels are reorganized.

The effect of cavity on conduction can be categorized into three axis:
(1) channel opening (enhancement) — collective coupling, photon-assisted processes and polariton delocalization enhanced mobility in disordered conductors [Orgiu et al., Nat. Mater. 14, 1123 (2015); Hagenmüller et al., PRL 119, 223601 (2017)];
(2) polaron blockade (suppression) — strong single-site coupling suppresses hopping exponentially, t → t·exp(−λ²/2), the light–matter analog of Franck–Condon blockade [Koch & von Oppen, PRL 94, 206804 (2005); Schaeverbeke et al., PRL 123, 246601 (2019)];
(3) decoherence — the same cavity-mediated coupling backscatters carriers breaking quantum Hall quantization [Appugliese et al., Science 375, 1030 (2022)].

See below for a scheamatics of our approach in this crossover:

Cavity control of charge transport: setup and panels.

Main panel. The transport geometry: a 2D crystal contacted to source and drain electrodes held at chemical potentials μ_L and μ_R (bias eV = μ_L − μ_R). An STM tip above the junction acts as a plasmonic nanocavity: the tip confines the electromagnetic field into a deep sub-wavelength hot spot on the crystal (white-hot focus). The red arcs are plasmons of wavelength λ created at the tip. This strongly coupled region lies right in the path of transport: the current therefore both senses and controls the local light–matter coupling.

In panels (a)–(c), the central region is reduced to its minimal version: a double quantum dot — two sites with onsite energies ε₁, ε₂ and interdot hopping t — tunnel-coupled to the leads (faint curved dashed arrows: injection from the left reservoir, extraction into the right one, at rates Γ_L, Γ_R). Hybridization splits the two-site spectrum into bonding and antibonding orbitals ε_± separated by 2t; these molecular levels, shown above each double dot, are the actual transport channels. The three panels realize three regimes of driving this two-level charge system with light:

– (a) Laser pumping. A classical light field of frequency ω (faint wiggly beam) shines on the double dot. This is photon-assisted tunneling in its classical form: the oscillating field lets a tunneling electron absorb or release energy in units of ħω, so each dot level acquires « copies » — sidebands shifted by ±nħω. When these copies fall inside the bias window, they act as extra transport channels and current can flow where it was otherwise blocked; if ħω matches the bonding–antibonding splitting 2t, the drive also directly excites the electron between the two orbitals.

– (b) Optical cavity. The same double dot placed at the antinode of a single quantized mode ħω_c between high-finesse mirrors (low loss κ). Here the coupling is to vacuum fluctuations rather than a classical field: at resonance 2t ≈ ħω_c the charge dipole and the photon hybridize into polaritons, shifting and splitting the transport channels even at zero or few-photon occupation — the Jaynes–Cummings counterpart of panel (a).

– (c) Plasmonic nanocavity. The STM-tip realization of the main panel: the mode volume is squeezed far below Vol ≈ λ³, so the vacuum coupling per photon is orders of magnitude larger than in (b), at the price of strong plasmonic loss. The double dot sits in the hot spot and is dressed by the confined field, with the same ε_± channel structure now strongly broadened and hybridized and should be treated by full quantum Rabi model.

– (d) Cavity-modified conduction. At weak coupling the I–V is the bare staircase (dashed); at moderate coupling, photon-assisted sidebands (a) or polariton branches (b, c) add channels at new thresholds, enhancing the current (green, shaded). At strong coupling the carrier dresses into a heavy polaron — the light–matter analog of Franck–Condon blockade — suppressing the current (red); the coupling λ thus sets the sign of the effect, implying an optimal λ of maximal current.

Thèmes

This EC-funded project studies how materials change their behavior when placed between tiny mirrors that trap light, so that electrons and light merge into new hybrid states. The theory maps how this trapped light alters the way such materials carry charge, spin, and heat, and how magnets can be steered with light. For advanced manufacturing, the key point is that material properties are set by the optical environment around the material — not by changing its chemistry. Function can thus be built in at the device-assembly stage, using the same structuring steps already common in chip and photonics production, and can even be re-tuned after fabrication. The project delivers the design rules connecting cavity layout to device performance, guiding future light-controlled sensors, low-power electronics, and thermal components.

• Dr. Fabio Pistolesi — Laboratoire Ondes et Matière d’Aquitaine (LOMA), Université de Bordeaux
• Dr. Rémi Avriller — Institut de Physique et Chimie des Matériaux de Strasbourg, Université de Strasbourg
• Dr. Clément Detrieux — Laboratoire Ondes et Matière d’Aquitaine (LOMA), Université de Bordeaux
• Dr. Akbar Jafari — Institute for Quantum Information, RWTH Aachen University

1. M. M. Sadeghi, M. Sarisaman, S. Rostamzadeh, Unlocking optical illusions: Transforming perception with optical null media, Opt. Laser Technol. 176, 111036 (2024).
2. M. Sarisaman, S. Tasdemir, S. Rostamzadeh, Topological behavior of spectral singularities in topological Weyl semimetals, J. Phys.: Condens. Matter 36, 405603 (2024).
3. S. Rostamzadeh, S. Tasdemir, M. Sarisaman, S. A. Jafari, M. O. Goerbig, Tilt-induced vortical response and mixed anomaly in inhomogeneous Weyl matter, Phys. Rev. B 107, 075155 (2023).
4. S. Rostamzadeh, M. Sarisaman, Charge–pseudospin coupled diffusion in semi-Dirac graphene, New J. Phys. 24, 083026 (2022).
5. S. Rostamzadeh, İ. Adagideli, M. O. Goerbig, Large enhancement of conductivity in Weyl semimetals with tilted cone, Phys. Rev. B 100, 075438 (2019).
6. A. Mostafazadeh, S. Rostamzadeh, Perturbative analysis of spectral singularities and their optical realizations, Phys. Rev. A 86, 022103 (2012).

Education

• Ph.D., Condensed Matter & Materials Physics — Sabanci University, Turkey (co-supervised at Université Paris-Saclay, France), 2019
• M.Sc., Theoretical Physics — Koc University, Turkey, 2011

Positions

• Marie Skłodowska-Curie Fellow (ADAGIO Programme) — LOMA, Université de Bordeaux, France, 2024–present
• Postdoctoral Fellow (CNRS) — Laboratoire de Physique des Solides, Université Paris-Saclay, France, 2022–2023
• Postdoctoral Fellow — Department of Physics, Istanbul University, Turkey, 2020–2022
• Postdoctoral Researcher — Sabanci University, Turkey, 2019–2020
• Visiting Doctoral Researcher (CNRS) — Laboratoire de Physique des Solides, Paris-Sud University, France, 2018

Fellowship

• Marie Skłodowska-Curie Postdoctoral Fellowship (ADAGIO) — Université de Bordeaux / LOMA, France, 2024–2027

Awards & Funding

• CNRS Postdoctoral Fellow — Université Paris-Saclay, France, 2022–2023
• Sabancı University & Lockheed Martin Corp. joint postdoctoral research funding, Turkey, 2019