Closed-cycle optical millikelvin magnet cryostat system for high-precision spectroscopy of lowest energy excitations

• Subject Area: Condensed Matter Physics
• Term: Funded in 2020
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 437187004

The major part of the applied system is an optical dilution refrigerator with optical of access along three axes using including an split-pair electromagnet as well as x-y-z and rotational nano-positioning for combined electrical and optical measurements. Therefore, an low-temperature objective with large NA is required. For the combined measurements of optical interband transition, low-energy collective excitations as well as transport properties of quantum states in novel van der Waals heterostructures and modulated quantum nano-structures that can be in-situ manipulated with electric and magnetic fields, millikelvin temperatures as well as additional optical and electronic equipment are required. In more detail, for resonant inelastic light scattering experiments and for photo-luminescence excitation spectroscopy, an ultra-narrow continuously tunable laser system in the wavelength range from 550nm to 1000nm is essential. The optical response of the quantum-nano-systems will be analyzed with a triple stage Raman spectrometer equipped with subtractive mode for stray light rejection and additive mode for enhancement of the energy resolution. The analyzed light is recorded either with a sensitive CCD camera or for time resolved measurements (>200ps) with an ICCD. This unique set-up will be used to study multiplex interaction phenomena as e.g. electron-electron, electron-phonon, spin-valley etc. interactions as well as emergent phenomena that are driven by these interactions such as superconductivity or (quantum-)phase transitions in novel quantum nano-systems. The goal is to develop a fundamental understanding of these fascinating systems and to learn in a next step to modify and tune their properties on purpose.

• DFG Programme: Major Research Instrumentation
• Major Instrumentation: Mischkryostat mit integriertem optischem Aufbau
• Instrumentation Group: 8550 Spezielle Kryostaten (für tiefste Temperaturen)
• Applicant Institution: Universität Münster
• Leader: Professorin Dr. Ursula Wurstbauer