Quantum Lab
The Quantum Material Device (QMD) Laboratory focuses on low-temperature charge and spin transport experiments in nanodevices of low-dimensional. The lab’s research spans two-dimensional materials, spintronics, and quantum sensors, making it a vibrant place for cutting-edge experiments. It also sets up a millikelvin facility for ultra-low temperature experiments.
The Quantum Material Device (QMD) Laboratory, or Quantum Lab, started in 2017 with Swedish Research Council (VR starting grant) funding. The lab initiated low-temperature charge and spin transport experiments in nanodevices of low-dimensional materials, which were fabricated at myfab cleanroom using cutting-edge nanofabrication tools such as photolithography and e-beam lithography. The ERC Consolidator Grant 2020 *SPINNER* allowed for extensive instrumentation on magneto-transport, integrated with nano-magneto-optic Kerr Effect measurements to investigate particularly low-dimensional magnets and their magneto-electric devices, along with new efforts for time-resolved ultrafast charge and spin transport & THz experiments. From 2020, we also put efforts into developing novel material growth facilities for materials using chemical vapor deposition techniques. With the Knut and Alice Wallenberg Foundation's project grant support in 2022, we are setting set up UU’s first millikelvin facility for 10 mK temperature with vector magnetic fields capacity (9:1:1 Tesla; expected to be commissioned in Feb 2025). Overall, the QMD lab enables us to perform a comprehensive set of state-of-the-art experiments in-house and to modernize our experimental capabilities. These experiments connect with our HAXPES laboratory, where we can characterize our samples with depth dependent element and chemical specific information with nm resolution. The quantum lab hosts a set of experiments for precision measurements and experiments on materials, which makes it a vibrant place for teaching our master courses, particularly for courses within our Master’s Program in Quantum Technology.
Quantum Material Device Laboratory (2017-2025)
Exploring atomically thin quantum materials
The Quantum Material Device Group is dedicated to researching quantum materials, developing cutting-edge quantum material devices, and exploring quantum phenomena related to the charge, spin, and orbital degrees of freedom of electrons. The purpose is to harness these phenomena for applications in energy-efficient spin memories and logic circuits, flexible spintronic devices, exotic quantum sensors, and intelligent spin-integrated and neuromorphic circuits. Our research focuses on two-dimensional (2D) materials such as graphene, MoS2, MoSe2, hBN, and 2D magnets, as well as their van der Waals heterostructures and quantum heterostructures with conventional thin films. We develop custom-built experimental setups to investigate spin transport, orbital phenomena, and magneto-optical effects at low temperatures (down to 10 millikelvins using a dilution refrigerator), unravel new charge and spin ordering, and explore emergent physics.
Nanofabrication processes at myfab cleanroom
Harnessing quantum phenomena
Leveraging spin and orbital angular momentum of electrons offers two powerful degrees of freedom that can advance spintronics and orbitronics—fields poised to revolutionize information technology. This holds enormous potential for breakthroughs such as ultrahigh-density memory and precision quantum sensing. The discovery of graphene and other 2D materials has sparked innovation in these areas, and we aim to understand and develop new charge, spin, and orbital devices, such as efficient spintronic devices using 2D materials, to move toward spin-integrated circuits and realize new quantum phases for advanced quantum sensors. This research involves cutting-edge nanofabrication at the Ångström Laboratory and precision measurements using newly established experimental setups in our group.
Experiments beyond the state-of-the-art
Our experiments encompass the growth of samples, novel device fabrication, and precision transport measurements down to millikelvin temperatures. We focus on exploring spin and orbital currents, their accumulation and ordering, ultrafast charge and spin transport in 2D heterostructures, and investigating magnetic textures and new quantum phases at ultralow temperatures. These experiments allow us to perform cutting-edge investigations and to uncover exciting new physics. Some of our recent finding and their implications are explained in the following.
Graphene has emerged as the ideal material for spin transport over length scales of the order of microns at room temperature, bringing fresh inspiration for planar pure spin current circuits with no net charge flow that could lead to low-power heatless electronics. In 2020, we demonstrated the longest spin communication capability of ~ 45 µm and the highest spin diffusion length of ~14 µm in CVD graphene in scalable devices (ACS Nano 14, 12771 (2020)). This record performance achieved in the scalable form of CVD graphene allows for exploring current spin functions and new concepts in spintronics, which we explore today. The actual device and non-local spin valve switching signal with the parallel and anti-parallel configuration of the injector and detector electrodes are shown in the adjoining figure.
Ultimate spin currents in graphene: Longest spin transport channel with lowest spin relaxation channel shown by spin valve signal. ACS Nano 14, 12771 (2020).
Flexible graphene spin devices with spin transport signals for temperature 77 K - 300 K. Nano Lett. 19, 666 (2019)
By constructing flexible graphene spin devices, we also realized highly diffusive graphene spin circuits (Nano Lett. 19, 666 (2019)). Despite the rough topography of the flexible substrates, these circuits prepared with chemical vapor deposited monolayer graphene reveal an efficient room-temperature spin transport with a distinctively large spin diffusion coefficient of ∼0.2 m2 s–1. The unprecedented experimental methodology allows us to explore advanced graphene spin circuits for setting a new performance benchmark and to explore strained 2D crystals.
At the QMD group, we also develop innovative growth techniques to grow directly van der Waals heterostructures. For example, realizing the direct growth of van der Waals heterostructures of MoS2 on graphene enabled us to investigate charge transfer dynamics effectively, revealing significant p-type doping effects (ACS Appl. Mater. Interfaces 2024, 16, 29, 38711–38722). Our time-resolved ultrafast transient absorption spectroscopy shows accelerated charge decay kinetics in the graphene/MoS2 heterostructures compared to standalone MoS2, facilitating the localized creation of photoactive regions in graphene channels.
Device prepared using directly grown MoS2 on graphene channels. ACS Appl. Mater. Interfaces 2024, 16, 29, 38711–38722
X-ray photoemission data revealing enhanced sp3 defects in graphene due to aluminum oxide layer on graphene. ACS Appl Mater Interfaces 14, 36209 (2022).
Our in-house X-ray Photoelectron Spectroscopy (XPS) characterization gives us a deeper understanding of interfaces in our devices. For instance, XPS measurements allow us to understand our samples' chemical and element specificity in graphene|metal oxide interfaces (ACS Appl Mater Interfaces 14, 36209 (2022)). This allowed us to detect the high-density sp3−defects for AlOx-based interfaces with graphene, which can cause additional resonant spin scattering in graphene spin valves and, in a way, suggests why graphene devices with AlOx tunnel barrier display lower spin lifetimes. At the same time, the Quantum Lab provides a state-of-the-art means for in-operando X-ray spectroscopy investigations.
People:
- M. Venkata Kamalakar (Associate Professor)
- Gopal Datt (Researcher)
- David Muradas Belinchón (PhD student)
- Henry Nameirakpam (PhD student)
- Chin-Yi Huang (PhD student)
- Umida Rayimjanova (PhD student)
- Gabriella Habtezion (MSc student)
- Christopher Borchert (Research assistant)
Contact
- Programme Professor Condensed Matter Physics of Energy Materials
- Håkan Rensmo
- Head of Division
- Nicusor Timneanu
- Visiting address: Ångström Laboratory, Lägerhyddsvägen 1, house 6, floor 0.