Condensed Matter in EMR: Strategic Vision for Science/Instrumentation/Techniques

EMR growth: Molecular Nanomagnetism Magnetic atoms with strong spin-orbit coupling 1D single-chain magnet Slow quantum dynamics JACS 2010, 132, 3980 Re4+: [Xe] 4f 14 5d 3 S = 3/2 T = 1.3 K

EMR growth: Ultra-high frequencies Two approaches: New THz-to-IR light sources, e.g. BigLight Existing sources, reduce propagation losses 1Long-term solution; 2short-term solution Low-loss quasi-optics & corrugated waveguide All-optical HF-EPR in split-gap magnet(s)

EMR growth: Quantum Matter New (emergent) physics at high magnetic fields Example: BaCuSi2O6 spin s = 1/2 dimer system (Han purple) f = 934 GHz BEC Sebastian et al., PRB 74, 180401(R) (2006); Nature 441, 617 (2006).

EMR growth: Low Temperatures Both 3He and 4He/4He dilution refrigerators Dedicated system in EMR lab Probes for high-field magnets Reasons for doing this: Access to new B,T phase space (quantum matter) Boltzmann, i.e. high B/T (esp. kBT << hf ) Suppress T2 processes, esp. conc. spin systems Enhanced sensitivity Long T2 → Pulsed EPR T-dependence of spin-relaxation processes Cavity Perturbation EPR under pressure (NSF CHE 0924374)

Quantum Information and Spintronics - HiPER EMR growth: Quantum Matter Quantum Information and Spintronics - HiPER Electron spin-echo detected ESR Nitrogen vacancies in diamond Takahashi et al., PRL 101, 047601 (2008); McCamey et al., PRL 102, 027601 (2009) The coupling between electron spins and their environment is a poorly understood subject of significant interest. In classical magnetism, this coupling leads to dissipation and damping of spin precession. In the quantum case, interaction with the environment leads to loss of quantum information. Overcoming decoherence is, thus, critical to spin-based quantum information processing. For spins in solids, coupling to surrounding fluctuating spins represents a major source of decoherence. One way to mitigate this decoherence is to bring the surrounding spin bath into a well-known quantum state that exhibits little or no fluctuations. However, full polarization of the spin bath is experimentally challenging. The nitrogen-vacancy (N-V) impurity center in diamond is one of the most promising solid-state spin systems (see [1]). By observing that the decoherence time, T2, of the N-V center saturates ~250ms at 8.5T and 2K, we have demonstrated that one can strongly polarize the spin bath and quench its decoherence. This work demonstrates that low-temperature, high-frequency pulsed electron paramagnetic resonance spectroscopy provides access to a new regime of spin decoherence in solids. Magnetic field (T) EPR signal Unique: 240 GHz ≡ 11.5 K 240 GHz ≡ 11.5 K

EMR growth: Upgrade of HiPER (ns EPR) In collaboration with the University of St. Andrews (G. Smith) and Thomas Keating LtD (R. Wylde), UK “Harness well-developed quasi-optical mm-wave technologies (95GHz & above) that provide a quantum leap in the performance of pulse ESR systems” 1 kW, 95 GHz amplifier Future upgrade to f > 200GHz To aid you – see Graham Smith abstract below. Points to remember…. Using optical techniques is a fundamentally different approach from all current commercial machines (+99% of home-made ones) Optics allows you to control the timing; cannot do this in a guided system due to unavoidable reflections This technology is easily scalable to higher frequencies (optics are broadband) Power only available recently at 95GHz to do this; will soon be possible at 200GHz, then 300 etc.. (where NHMFL steps in) Need to REALLY emphasize (physicists won’t have a clue): 95GHz is VERY high-field/frequency for state-of-the-art bio. EPR 95GHz commercial systems have <1W, so forced to use longer pulses and cavities that lead to time resolution ~100ns & low sensitivity Point out that they will see something similar on the tour (low power and developed here – optics not to the level of HiPER) Next slide and abstract outlines additional rationale for wanting to do pulsed EPR at 95GHz and above Pulsed Double Electron-Electron Resonance (DEER) spectroscopy in combination with site directed spin labeling, is a powerful technique for accurate long-range distance measurements in biomolecules. Today, the vast majority of these measurements are run at 10 GHz, but more recently there has been interest in moving to higher magnetic fields in order to be sensitive to the relative orientation of the nitroxide pairs. Proof of principle experiments have recently been carried out at 180 GHz and 95 GHz, which have clearly indicated the potential of this methodology. However, these experiments also suffered from relatively low sensitivity due to the low source power available, which in turn required the use of high Q cavities. At St Andrews, a high power kW pulse system at 94GHz has been developed which also features very low deadtime. This system can deliver effective 5 ns π/2 pulses to high volume non-resonant sample holders, at any desired frequency over 1GHz instantaneous bandwidths. This allows near optimal pulses to be delivered for DEER experiments at any frequency across the full 500 MHz spectral width of a nitroxide spectrum at 94 GHz. This not only offers very high sensitivity but allows all relative nitroxide pair orientations to be correlated separately and hence becomes sensitive to small angular shifts in the relative angular positions of the nitroxide pairs. This methodology holds great promise in being able to characterise small conformational changes in biomolecules even in the presence of broad distance distributions or where the nitroxides have a large inherent degree of flexibility in their relative orientation. In this paper, we will outline the general experimental methodology and analysis and give recent experimental results that indicate the potential of the technique. Manipulate and detect spins on nanosecond and sub-nanosecond timescales Demonstrate significant gains in sensitivity for pulse EPR with low deadtime HiPER: kW pulses as short as 800 ps  can operate over 1GHz bandwidth ns deadtime  reflected pulses attenuated -80dB within 1-2 ns! THIS IS ONLY POSSIBLE OPTICALLY AND ONLY POSSIBLE AT 95 GHz AND ABOVE

EMR growth: personnel/staffing Significant growth in program has so-far occurred without a corresponding growth in the number of postdocs and students This is taking its toll on the user support staff More and more time devoted to user support Less time on proposal and instrument development