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Nanoscale magnetometry using quantum mechanical spin; the Nitrogen Vacancy
(NV-) center in diamond
Kapildeb Ambal
National Institute of Standards and Technology, Gaithersburg, Maryland 20899
Institute for Research in Electronics and Applied Physics, University of Maryland, College
Park, MD 20742
Outlines
2
Magnetic Resonance
Electron Spin Resonance (ESR)/Electron Paramagnetic Resonance (EPR)
Optically Detected Magnetic Resonance (ODMR)
Nitrogen Vacancy (NV) Center
Magnetic field sensing using Nitrogen Vacancy (NV-) Center
Spin-wave detection of nano-magnet using Nitrogen Vacancy (NV-) Center
continuous-wave Electron Spin Resonance (cw-ESR)
3
Q
S = 1/2
𝒉𝝂 = 𝒈𝒆𝝁𝐁𝑩𝟎
ms = +1/2
ms = -1/2
Magnetic field
Ener
gy
𝜔𝐿 = − 𝛾𝐵0 = 𝜔0
B1
B0
M0
K. Ambal et al., Phys. Rev. Applied 4, 024008 (2015)
pulsed-Electron Spin Resonance (p-ESR)
4
B0
M0
Laboratory frame Rotating frame
M0B1
M
𝜔1 = − 𝛾𝐵1 𝛼 = −𝛾 𝐵1 𝑡
𝒉𝝂 = 𝒈𝒆𝝁𝐁𝑩𝟎
ms = +1/2
ms = -1/2
Magnetic field
Ener
gyx
y
z
M0
xy
z
B0
𝜔𝐿 = − 𝛾𝐵0
Spin lattice relaxation time (T1 time)
5
M0
Thermal equilibrium
timesi
gnal
B0
𝑀 = 𝑀0 [1 − 2 𝑒−𝑡𝑇1]
M0
Thermal equilibrium
B0B0
M0B1
M
Microwave ON𝜋 pulse
𝛼 = −𝛾 𝐵1 𝑡
B0
Pros and cons of ESR
6
Spectroscopic access of the atomic environment of electron spin
Average distance between spins
Relaxation mechanism
Spin counting
Chemical identity (g factor)
Polarization dependent higher magnetic field better signal
Less sensitive for thin film samples
Expensive equipment needed for the purpose
Minimum of 109 spins are required to get a signal
Optically Detected Magnetic Resonance (ODMR)
7
𝒉𝝂 = 𝒈𝒆𝝁𝐁𝑩𝟎
ms = +1/2
ms = -1/2
Magnetic field
Ener
gyElectro-luminescence Photo-luminescence
Baker et. al, Nat. Comm. 3, 898 (2012).
Why ODMR?
8
Advantages
Highly sensitive Can even detect single spin
Works for thin film devices
Works for low magnetic field
Equipment cost much less
Charge transport dynamics
Charge recombination dynamics
Quantum sensing
Nitrogen Vacancy (NV) center in diamond
9
Atom sized crystal defect
Optically active
Quantum sensing
Works at room temperature
Long coherence time at room temperature A. Haque et al., J. Manuf. Mater. Process 1, 6 (2017)
5.5eV
Ev
Ec
Ground state
Excited state
Formation of Nitrogen Vacancy (NV-) center
10
Nitrogen [N+ ]implantation
Diamond substrate
LatticeVacancy
NV centers
1000 oC
29.5 x103 Counts/s
4.3 x103
Confocal microscopy image
Experimental setup: confocal microscopy
11
Confocal microscopy
B0
cw-ODMR using NV- center
12
532 nm
MW
Read
Quantum sensing; DC magnetometry using NV- center
13
2γB0
Optically detected magnetic resonance (ODMR)
𝐵 =∆𝑓02𝛾
Signal processing for realtime DC magnetometry
14
Modulation
Lockin Amplifier
Quantum measurement Modulated pulse rate Demodulation problem
532 nm
Signal processing; demodulation Concept
15
Modulation
Quantum measurement Modulated pulse rate Demodulation concept
Signal out
K. Ambal et al., US patent 16/519,755 (pending)
cw-ODMR; counter vs ratemeter
16
cw-ODMR: frequency modulated
17
Sensitivity: 4.1 µT/Hz1/2
mod = 500 Hz
K. Ambal et. al., Rev. Sci. Instrum. 90, 023907 (2019)
Continuous magnetometry using NV- center
18
K. Ambal et al., Rev. Sci. Instrum. 90, 023907 (2019).
K. Ambal et al., US patent 16/519,755 (pending)
Realtime magnetometry using NV- center
19
Real-time measurement of magnetic field sweep rate up to 50 µT/s
K. Ambal et. al., Rev. Sci. Instrum. 90, 023907 (2019)
K. Ambal et. al., US patent 16/519,755 (pending)
Pulsed-optically detected magnetic resonance (pODMR)
20
B0
sig
532 nm
MW
Read
Spin lattice relaxation time of NV- center
21
|1⟩Initialize ⟩|0 Readout. . .t
T1 relaxometry
22M. Pelliccione et al., Phys. Rev. Applied 2, 054014 (2014)
equilibriumOptical polarization
|1⟩Initialize ⟩|0 Readout. . .𝜏
M0 M0B1
M
Thermal equilibrium
Microwave ON𝜋 pulse𝛼 = −𝛾 𝐵1 𝑡
Magnetism
23
Medical imagining
Vehicle brakingInformation storage
Advances in magnetism
24
Capacity: 5 MB or 1 songCapacity: 4 TB or 800,000 songs
1956, IBM2016, Seagate
Future of magnetic technology
25
Magnetic Random Access memory
Nonvolatile: Holds data in the event
of a power outage
Magnetic memory will be small, fast,
numerous.
Magnetic random access memory (MRAM)
26
“0”“1”
Free layer
Barrier layer
Fixed layer
Magnetic tunnel junction (MTJ)
Static and dynamic properties of “free layer” determine device properties
Static properties:CoercivityExchange
Dynamic properties:Spin wave modesFerromagnetic resonance
Thermal spin wave modes
27
Bapp
T1 relaxometry spin wave mode detection
28
1
𝑇1=
1
𝑇10 +
𝛾2
2⟨𝑆𝐵𝑥 + 𝑆𝐵𝑦⟩
Spectral density [T2/Hz]
Bapp
Conclusions
29
Realtime DC magnetometry using quantum sensor
Magnetic noise spectroscopy of nanomagnet
Acknowledgement
30
Robert D. McMichael
Sergey Dushenko
Cooperative Research Agreement # 70NANB14H209
Questions
31
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