Room-Temperature Electrical Readout of Spin Defects in van der Waals Materials

Abstract

Negatively charged boron vacancy ($\mathrm{V_B^-}$) in hexagonal boron nitride (hBN) is the most extensively studied room-temperature quantum spin system in two-dimensional (2D) materials. Nevertheless, the current effective readout of $\mathrm{V_B^-}$ spin states is carried out by systematically optical methods. This limits their exploitation in compact and miniaturized quantum devices, which would otherwise hold substantial promise to address quantum sensing and quantum information tasks. In this study, we demonstrated a photoelectric spin readout technique for $\mathrm{V_B^-}$ spins in hBN. The observed photocurrent signals stem from the spin-dependent ionization dynamics of boron vacancies, mediated by spin-dependent non-radiative transitions to a metastable state. We further extend this electrical detection technique to enable the readout of dynamical decoupling sequences, including the Carr-Purcell-Meiboom-Gill (CPMG) protocols, and of nuclear spins via electron-nuclear double resonance. These results provide a pathway toward on-chip integration and real-field exploitation of quantum functionalities based on 2D material platforms.

Figures (4)

• Figure 1: Schematic illustration and basic results of PDMR. (a) Illustration of the charge dynamics: (1) Single-photon excitation promotes electrons to the excited state (ES), which can relax to the ground state (GS) or metastable state (MS) via spin-dependent intersystem crossing; (2) additional photon absorption elevates electrons to the conduction band; (3) charge repumping and carrier separation generate the photoelectric signal. (b) Experimental setup for photoelectric readout. (c) Timing sequence for pulsed PDMR. The signal demodulated using the TTL reference captures the microwave-induced signal. (d) Representative PDMR spectrum at 14 mT. (e) Magnetic field–dependent PDMR spectral map of the$m_s=\pm1$ states at $-2.3$ V bias and 2 mW laser power.
• Figure 2: Dependence of PDMR signal and photocurrent on bias voltage and laser power. (a) Photocurrent as a function of applied bias voltage under 2 mW laser excitation. (b) Photoluminescence counts (blue squares) and photocurrent (red circles) versus laser power at a fixed bias of 2.3 V. The red curve is a quadratic fit to the photocurrent: $y=y_0+ax+bx^2$. (c) PDMR spectra at 14 mT under varying bias voltages. (d) PDMR contrast and SNR (red squares) and ODMR contrast and SNR (blue circles) as functions of laser power at 2.3 V bias.
• Figure 3: Coherent measurements of Rabi oscillations and dynamical decoupling of boron vacancies. (a) The top panel shows the timing sequence for Rabi measurements. Red dots indicate photoelectric readout data, and the red line is the corresponding fit. The inset displays the Rabi frequency as a function of MW driving strength. (b) The top panel shows the timing sequence for the CPMG measurement, with the first half labeled as the signal and the second as the reference. The bottom panel presents experimental results for CPMG sequences with 1 to 512 $\pi$ pulses. The inset shows the extracted coherence time versus the number of $\pi$ pulses on a log2 scale.
• Figure 4: Photoelectric readout of nuclear spins. The upper and lower subpanels correspond to the $m_s = 0$ and $m_s = -1$ states, respectively, with timing sequences shown in the lower-left corner of each. For the $m_s = 0$ state, nuclear resonance is detected by sweeping the RF field. For the $m_s = -1$ state, an external MW $\pi$ pulse is applied to flip the electron spin before RF excitation. Red triangles represent data for the $m_s = 0$ state and blue circles for $m_s = -1$, with corresponding Gaussian fits shown as red and blue curves.