Martin Brandt

Experimental Semiconductor Physics

Technical University of Munich

Walter Schottky Institut

Am Coulombwall 4

85748 Garching

Tel. +49 89 289 12758


Group webpage


Research focus: dopants and defects in semiconductors for quantum applications, EPR, ESR

The Brandt group studies the fundamental properties of paramagnetic states in semiconductors for quantum applications. These states include dopants such as phosphorus in silicon, where both the electronic spin as well as the spin of the nucleus can be used as a quantum resource. In isotopically pure 28Si, the latter system has a coherence time of tens of minutes, rendering 28Si:P a unique and highly useful quantum material. The group investigates the interactions between these spins and with their environment and develops methods to tune the spin properties e.g. via strain. For these investigations, the group in particular uses advanced pulsed electron spin resonance techniques.

Approaches to increase the sensitivity of magnetic resonance experiments are a particular focus of the research activity. Spin selection rules govern charge transport processes and allow the readout of quantum states. The Brandt group is spearheading these electrically detected magnetic resonance (EDMR) techniques and uses them to prepare spins at dopants or defects in silicon and other semiconductors and to understand spin-to-charge and spin-to-photon conversion. Both spin-dependent recombination as well as spin-dependent photoexcitation are employed for this. Of particular current interest is the electrical readout of NV- centers in diamond, which the group has recently demonstrated to be highly efficient.

Selected publications

  • Multiple-Quantum Transitions and Charge-Induced Decoherence of Donor Nuclear Spins in Silicon, Phys. Rev. Lett. 118 , 246401 (2017)
  • Efficient Electrical Spin Readout of NV? Centers in Diamond, Phys. Rev. Lett. 118 , 037601 (2017)
  • Interaction of Strain and Nuclear Spins in Silicon: Quadrupolar Effects on Ionized Donors, Phys. Rev. Lett. 115 , 057601 (2015)


Echo Trains in Pulsed Electron Spin Resonance of a Strongly Coupled Spin Ensemble

S. Weichselbaumer, M. Zens, C.W. Zollitsch, M.S. Brandt, S. Rotter, R. Gross, H. Huebl.

Physical Review Letters 125, 137701 (2020).

Show Abstract

We report on a novel dynamical phenomenon in electron spin resonance experiments of phosphorus donors. When strongly coupling the paramagnetic ensemble to a superconducting lumped element resonator, the coherent exchange between these two subsystems leads to a train of periodic, self-stimulated echoes after a conventional Hahn echo pulse sequence. The presence of these multiecho signatures is explained using a simple model based on spins rotating on the Bloch sphere, backed up by numerical calculations using the inhomogeneous Tavis-Cummings Hamiltonian.


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