Probing quantum coherence in single-atom electron spin resonance

Willke, Philip; Paul, W.; Natterer, Fabian Donat; Yang, Kai; Bae, Yujeong; Choi, Taeyoung; Fernández-Rossier, J.; Heinrich, Andreas; Lutz, Christopher P.

doi:10.1126/sciadv.aaq1543

Cited by 100 publications

(209 citation statements)

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“…This nonlinear process is enhanced near the resonance condition and depends on the square of the driving amplitude, which is compatible with Ref. [19]. The effect is based on a current-induced spin-torque and does not assume any effective time dependence of the local moment Hamiltonian.…”

Section: Discussionsupporting

confidence: 83%

Spin transfer torque induced paramagnetic resonance

2019

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We show how the spin-transfer torque generated by an ac voltage may be used to excite a paramagnetic resonance of an atomic spin deposited on a metallic surface. This mechanism is independent of the environment of the atom and may explain the ubiquity of the paramagnetic resonance reported by Baumann et al. [Science 350, 417 (2015)]. The current and spin dynamics are modeled by a time-dependent Redfield master equation generalized to account for the periodic driven voltage. Our approach shows that the resonance effect is a consequence of the nonlinearity of the coupling between the magnetic moment and the spin-polarized current which generates a large second-harmonic amplitude that can be measured in the current signal.

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Section: Discussionsupporting

confidence: 83%

Spin transfer torque induced paramagnetic resonance

2019

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“…We find a zero-RF drive Γ of (2.5 ± 0.2) mT and a corresponding coherence time of 2 * of (4.5 ± 0.4) ns. This represents a lower bound for the intrinsic T2 because additional broadening mechanisms related to the vibrational stability of the tip [7], magnetic fluctuations [23], and decoherence by tunneling electrons [23] have not been accounted for.…”

Section: B Esr Demonstrationmentioning

confidence: 99%

Upgrade of a low-temperature scanning tunneling microscope for electron-spin resonance

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Patthey

Bilgeri

et al. 2019

Review of Scientific Instruments

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Electron spin resonance with a scanning tunneling microscope (ESR-STM) combines the high energy resolution of spin resonance spectroscopy with the atomic scale control and spatial resolution of STM. Here we describe the upgrade of a helium-3 STM with a 2D vector-field magnet (Bz = 8.0 T, Bx = 0.8 T) to an ESR-STM. The system is capable of delivering radio frequency (RF) power to the tunnel junction at frequencies up to 30 GHz. We demonstrate magnetic field-sweep ESR for the model system TiH/MgO/Ag(100) and find a magnetic moment of (1.004 ± 0.001) B. Our upgrade enables to toggle between a DC mode, where the STM is operated with the regular control electronics, and an ultrafast-pulsed mode that uses an arbitrary waveform generator for pump-probe spectroscopy or reading of spin-states. Both modes allow for simultaneous radiofrequency excitation, which we add via a resistive pick-off tee to the bias voltage path. The RF cabling from room temperature to the 350 mK stage has an average attenuation of 18 dB between 5 and 25 GHz. The cable segment between the 350 mK stage and the STM tip presently attenuates an additional 34+5−3 dB from 10 to 26 GHz and 38+3−2 dB between 20 and 30 GHz. We discuss our transmission losses and indicate ways to reduce this attenuation. We finally demonstrate how to synchronize the arrival times of RF and DC pulses coming from different paths to the STM junction, a prerequisite for future pulsed ESR experiments.

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“…Berggren and Fransson [13] proposed that the spin polarization of the electrodes generates a finite time dependence of the uniaxial and transverse anisotropy with the ac signal. They showed that this change leads to a finite ESR signal in integer spin systems, and they predicted a dependence of the ESR frequency on the tip-sample distance, a shift that has not been observed in recent experiments [4] when changing the current by a factor of 30.…”

Section: Introductionmentioning

confidence: 88%

“…The demonstration of reproducible single-atom [1] and single-molecule [2,3] electron spin resonance (ESR) has opened in the analysis of surface science at the atomic scale. Conserving the atomic spatial resolution of the scanning tunneling microscopy (STM), STM-ESR provides unprecedented energy resolution in the neV energy scale [4]. Moreover, it can be combined with high time resolution pump-and-probe techniques [5,6].…”

Section: Introductionmentioning

confidence: 99%

Cotunneling mechanism for all-electrical electron spin resonance of single adsorbed atoms

et al. 2019

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The recent development of all-electrical electron spin resonance (ESR) in a scanning tunneling microscope (STM) setup has opened the door to vast applications. Despite the fast-growing number of experimental works on STM-ESR, the fundamental principles remain unclear. By using a cotunneling picture, we show that the spin resonance signal can be explained as a time-dependent variation of the tunnel barrier induced by the alternating electric driving field. We demonstrate how this variation translates into the resonant frequency response of the direct current. Our cotunneling theory explains the main experimental findings. Namely, the linear dependence of the Rabi flop rate with the alternating bias amplitude, the absence of resonant response for spin-unpolarized currents, and the weak dependence on the actual atomic species.

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Probing quantum coherence in single-atom electron spin resonance

Abstract: Phase coherence of single-atom spins on surfaces is investigated in a scanning tunneling microscopy experiment.

Cited by 100 publications

References 50 publications

Spin transfer torque induced paramagnetic resonance

Spin transfer torque induced paramagnetic resonance

Upgrade of a low-temperature scanning tunneling microscope for electron-spin resonance

Cotunneling mechanism for all-electrical electron spin resonance of single adsorbed atoms

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