Precision Measurements with Polyatomic Molecules Nick Hutzler - - PowerPoint PPT Presentation
Precision Measurements with Polyatomic Molecules Nick Hutzler Caltech Internal Fields Thanks Naftali, Alexander for EDM introduction and motivation! Atoms/molecules have extremely large fields Relativistic ~Z 2-3 enhancement
▪ Relativistic ~Z2-3 enhancement ▪ Up to 106 enhancement over lab fields
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|↓ |↑
▪ Problem – constituents experiences zero average field!
▪ Atom/molecule states always have this symmetry in free space
▪ Solution: polarize
▪ Apply lab field to orient atom/molecule ▪ Interaction no longer averages to zero ▪ Sensitivity polarization P
▪ Requires mixing opposite parity states, ε > d/Δ
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▪ Atoms
▪ ~ 100 THz (electronic) ▪ P ~ 10-3 @ 100 kV/cm
▪ Molecules
▪ ~ 10 GHz (rotational) ▪ P ~ O(1) @ 10 kV/cm
▪ “Molecules are 1000x more sensitive” ▪ Some molecules have parity doublets, <10 MHz
▪ Enables full polarization in small fields… and more!
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Atoms ~ 100 THz Molecules ~ 10 GHz
J
Parity Doubling ~ 10 MHz
J+ J–
▪ Harvard, Yale, Northwestern ▪ Molecular beam spin precession in ThO ▪ Current best limit on the electron EDM
▪ |de| < 1.1 x 10-29 e cm ▪ Statistics limited ▪ ~100x eEDM improvement in past since 2006 National Academies report!
▪ Already probing the TeV scale – beyond the LHC
▪ ~3-30 TeV for 1 or 2 loop couplings to new CPV physics
▪ Molecules are worth it!
▪ Not just more sensitive, but more robust
ACME Collaboration, Nature 562, 355 (2018) www.electronedm.info
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= 0 Time E B Time
E B
H = − dE − B
+ = B + dE - = B − dE
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= 0 Time E B Time
E B
H = − dE − B
+ = B + dE + ??? - = B − dE +???
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dE / B < 10-6
▪ Parity doublets enable full polarization and “internal comagnetometer states”
▪ A.k.a. “spectroscopic reversal”
▪ Huge advantages!
▪ Smaller fields ▪ EDM sensitivity saturated, independent of field ▪ Measure without field reversals ▪ Systematics amplified in other channels ▪ Enables ion trap measurements (JILA method)
▪ Just as important as sensitivity increase (in my opinion)
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▪ Polarization requires ~1,000x smaller fields
▪ Simpler engineering, enhanced quality of life ▪ Directly suppresses geometric phases, motional fields, leakage currents, etc.
▪ (These are serious! n, Tl, …)
▪ Also suppresses many systematics for optically trapped species
▪ Polarization can be saturated
▪ EDM no longer depends on E field, most systematics would
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▪ Perform measurement in two “flipped” molecular states ▪ Cancels field-related systematics with high fidelity
▪ Systematics amplified in field flipped channel
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▪ Error ~ 10-27 e cm/mG
▪ Proof of systematic error suppression ▪ Resource for hunting systematics
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EDM Asymmetry EDM Asymmetry
With molecule flip Without molecule flip
▪ JILA needs spectroscopic reversal since can’t flip E field in an ion trap ▪ Both ACME and JILA rely on them for systematic robustness
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▪ Don’t exist in atoms (in the sense that I mean…) ▪ In diatomics, we have Λ (or Ω) doubling
▪ Projections of Lelec along internuclear axis are nearly degenerate ▪ Split by Coriolis-type interactions with rotation ▪ Similar in nuclei!
▪ Requires electronic orbital angular momentum
▪ Rules out lots of interesting species!
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J
+ –
Rotation Lelec +𝚳 −𝚳
▪ Polyatomic molecules generically have parity doublets
▪ Effectively independent of electronic structure, atom choice ▪ Comparable complexity to diatomics (discussed here…)
▪ Only way to access parity doublets for many exciting species
▪ Ba, Ra, Yb, Hg, Tl, …
▪ Generically opens up many
▪ Only way to combine CPV sensitivity, parity doublets, and ultracold techniques
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▪ Example: linear triatomic
▪ MOH, MCCH, …
▪ Three mechanical modes ▪ Bending mode is doubly degenerate ▪ Eigenstates have orbital angular momentum ℓ ▪ Coupling of ℓ to rotation creates parity doublet
▪ Typically ~ 10 MHz ▪ Independent of electronic structure!
▪ Symmetric tops – rotations about symmetry axis
▪ Splittings even smaller ▪ MCH3, MOCH3, …
▪ Doesn’t interfere with laser cooling
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ℓ ℓ
Symmetric stretch Asymmetric stretch
Bend
▪ 106 molecules ▪ 10 s coherence ▪ Large enhancement(s) ▪ Robust error rejection ▪ Efficient control/readout ▪ 1 week averaging
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Mnew phys ~ 1,000 TeV (!) Beyond the reach of conceivable accelerators
Even before implementing truly advanced quantum techniques, such as squeezing, interaction engineering, …
Figure adapted from A. J. Daley, Nature 501, 497 (2013)
So… how to build this?
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Many people are working on this, with many recent and exciting results! Precision measurements, quantum chemistry, many-body, information, …
▪ Forces, including dissipative, from photon scattering momentum kicks
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Yb Atoms
▪ Requires many (~105) cycles
decay ▪ Decay to other states stops the cooling process ▪ Internal vibrational, rotational levels are excited in decay ▪ For carefully chosen molecules, this is manageable ▪ Most of the leaders and pioneers in this area are in the room!
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Ground Excited Other
Decay
Ground Excited “Atoms” “Molecules” Rotation, vibration, …
Laser Excitation
▪ Requires many (~105) cycles
decay ▪ Decay to other states stops the cooling process ▪ Internal vibrational, rotational levels are excited in decay ▪ For carefully chosen molecules, this is manageable ▪ Laser cooled and trapped molecules now exist!
▪ SrF (DeMille, 2014) ▪ CaF (Tarbutt 2017, Doyle 2017) ▪ YO (Ye, 2018)
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Ground Excited Other
Decay
Ground Excited “Atoms” “Molecules” Rotation, vibration, …
Laser Excitation
▪ Generally works for molecules with metal- centered s orbital(s)
▪ Alkaline-earth (s2) ▪ Single bond to halogen (F)
▪ Orbital hybridization pushes electron away from chemical bond
▪ Decouples electronic, molecular excitations
▪ Works for many bonding partners – polyatomics!*
▪ Laser cooling comes from metal centered electron ▪ Shown with SrOH (Doyle, 2017)
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*T. A. Isaev and R. Berger, PRL 116, 63006 (2016), *I. Kozyryev, et al., ChemPhysChem 17, 3641 (2016)
▪ CPV sensitivity also comes from electronic structure
▪ Core-penetrating s electrons ▪ Several laser-coolable options, including at this workshop! ▪ BaF, HgF, RaF, TlF YbF, …
▪ Polyatomic analogues have similar sensitivity
▪ CPV comes from metal center ▪ Explicitly shown for BaOH, RaOH, RaOH+, ThOH+, TlCN, YbOH (so far)
▪ Why polyatomics?
▪ Access to parity doublets! ▪ MF → MOH, MOCH3, …
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Core-penetrating
CPV sensitivity
▪ ThO, WC, TaN, HfF+, … ▪ “Requires” Lelec > 0 ▪ Interferes with laser cooling
▪ YbF, BaF, RaF, TlF, … ▪ “Requires” Lelec = 0 ▪ No internal comagnetometers ▪ Similar story for assembled molecules (HgLi, YbCs, …)
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▪ ThO, WC, TaN, HfF+, … ▪ “Requires” Lelec > 0 ▪ Interferes with laser cooling
▪ YbF, BaF, RaF, TlF, … ▪ “Requires” Lelec = 0 ▪ No internal comagnetometers ▪ Similar story for assembled molecules (HgLi, YbCs, …)
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▪ YbOH is ideal candidate ▪ Previously existing spectroscopy ▪ Laser coolable ▪ Several calculations of Eeff (including Bhanu Das)
▪ Eeff = 23.4 GV/cm
99, 042512 (2019)
▪ Broad sensitivity to new physics via multiple stable, abundant isotopes
▪ eEDM (174), NMQM (173), NSM (171), AM (171), …
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Science state
▪ Me @ Caltech ▪ John Doyle @ Harvard ▪ Tim Steimle @ ASU ▪ Amar Vutha @ Toronto
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MQMs violate P, T, CP
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▪ Nucleon EDM ▪ quark EDM/chromo-EDM ▪ CPV nuclear forces ▪ Strong CPV (θQCD) ▪ …
▪ Collective enhancement ▪ ≈ β2Z
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Rotating EDM produces MQM
173YbOH NMQM Experiment @ Caltech
▪ 173Yb (I=5/2), quadrupole deformed ▪ Recent calculation supports 173YbOH ≈ 173YbF
▪ arXiv:1906.11487
▪ Cryogenic buffer gas beam experiment ▪ Laser cooling, trapping in future generations?
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▪ Best, new-ish technology for intense, cold, and slow molecular beams ▪ >100x more intense, >3x slower than supersonic beams (“jets”)
▪ Usually much more! ▪ Especially for reactive or refractory species ▪ Not a jet source
▪ Currently used by ACME, CeNTREX, all molecule laser cooling experiments
▪ Critical to all of these
▪ Works for just about anything, atoms, small molecules, large biological molecules, …
Buffer Gas Fill Line
Hot YbOH 4 K Copper Cell Pulsed Laser
Yb(OH)3
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▪ Enhance chemical production of YbOH in buffer gas beam
▪ Ablate Yb+Yb(OH)3 ▪ Excite Yb 1S0 → 3P1, 556 nm ▪ Yb(3P1) reacts with ??? to create YbOH
▪ ~10x beam signal increase
▪ Typically ~1010-11 out of cell ▪ More in future? Plenty of unreacted Yb…
▪ Demonstrated for 173, 174 ▪ Also works for bending mode! ~109-10 bending molecules directly out of source ▪ Should work for lots of things, especially Ba and Ra!
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▪ DF, LIF, MODR, etc.
173,174YbOH
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▪ Branching ratios for laser cooling measured ▪ Efficient optical pumping pathway into bending mode
▪ Slow beams created from 2 K sources ▪ Photon cycling, radiative forces, 1 D cooling observed
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▪ If bonding partner doesn’t matter, why not make it
▪ Enhanced optical forces ▪ “Quantum logic” type
▪ …
▪ Only theory so far, but approach seems promising ▪ Molecules Functionalized with Optical Cycling Centers (MFOCCs)
▪ Wes Campbell, Anastassia Alexandrova, Justin Caram, John Doyle, Eric Hudson, NRH, Anna Krylov
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Yb−C≡C−Ca Behaves like two cycling centers
PRA 100, 022502 (2019)
▪ Especially atoms in the middle of orbital filling ▪ Many interesting species! ▪ Cycling center could offer cooling, control, readout
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Summary: Polyatomic molecules offer a unique way to combine molecular enhancement with experimental robustness from parity doublets in a way that is independent of specific atomic properties. We can therefore realize these with laser- coolable species, exotic species, and more. Thanks for your attention! Special thanks for the invitation Come visit us! www.hutzlerlab.com www.polyedm.com