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the Baker · solid and liquid in the same body
Split Zero
Split Zero is Tilt’s big brother. He got here first, and he’ll tell you that means he outranks him. Tilt only needs pressure. Split needs pressure and heat.
“Hold the frame. Let the rest run.”
His symbol is ≐: an equals sign with a dot riding on top. The two bars hold still; the dot doesn’t. Unicode names it “approaches the limit.” Split Zero is a state split in two: solid and liquid in the same body at once.
The frame stays put, and the part that moves is what makes it rise.
He works there
The Fibonacci Fractal Bakery · the lamination station · Nashville
Split Zero works at the Fibonacci Fractal Bakery, at the lamination station. He makes the 89-layer Fibonacci Croissant.
He can’t just hang out like Tilt, because his power needs the oven. Tilt can work wherever the pressure is, and he lives at The Culet. Split exists only where someone can bring the heat, and in Nashville that’s the bakery’s kitchen. That’s why he took the job: the oven comes with it.
Split holds the frame and lets the rest run. In his ice, the oxygens lock into a rigid lattice while the hydrogens flow through it like a liquid. A croissant works the same way. The dough layers hold their shape in the oven while the butter melts, and the water in it turns to steam that pushes the layers apart.
Bakery and squad ties
Specialty: layers that stay layers under heat that would melt anyone else. Tell: everything he touches conducts. A superionic layer carries current; so does a Split Zero shift.
π Dr. Penelope “Pi” Crust, the founder who hired him. She needed someone who could keep 89 layers distinct when the oven hits full heat.
~ Professor Max “Sine Wave” Dougherty, his closest partner. Max runs the ovens and Split runs the layers; neither can do the other’s job.
∠ Tilt Zero, his little brother and the one who does the rolling. Lamination is pressure first, then heat: Tilt presses the dough flat, Split bakes it. That’s the order of the 2021 diamond-cell run below, where the water was squeezed to 150 GPa first and laser-heated after. (The 2019 shock experiment did both at once.)
0÷2 Half Zero, often confused with Split. Half is a number cut in half; Split is a state cut in two.
The ground under it
Split Zero is superionic ice. Physics World puts it at tens or even hundreds of GPa of pressure at temperatures above 1000-2000 K
, where protons run through a solid oxygen lattice. Simulations suggest its ionic conductivity may exceed 100 siemens per centimetre, which Physics World calls almost as conductive as metals
.
| Year | Team | Pressure and heat | What they found |
|---|
| 2026 (preprint Oct 2025) | Forestier, Weck et al., CEA, Physical Review Letters | 80 to 229 GPa, 300 to 2,630 K, laser-heated diamond cell | A third superionic phase, hcp, built from stacked layers. Physics World reports it emerging at 130 to 200 GPa above 1,800 K; the preprint says it dominates above 200 GPa. |
| 2026 | Andriambariarijaona et al., Nature Communications | Laser-driven multiple shocks, up to about 180 GPa, ultrafast X-ray diffraction at free-electron lasers | At pressures exceeding 150 GPa and temperatures around 2500 K, our diffraction patterns challenge the pure FCC-SI phase model : evidence of a mixed close-packed superionic phase. |
| 2021 | Prakapenka, Holtgrewe, Lobanov, Goncharov, Nature Physics | 150 GPa, then laser-heated to 6,500 K | Body-centred and face-centred cubic superionic ice mapped in a static cell. Lobanov: about the upper third of both planets is liquid , with solid superionic ice deeper down. |
| 2019 | Millot, Coppari et al., Lawrence Livermore, Nature | Laser shock waves, several thousand degrees, lasting billionths of a second | Oxygen in a face-centered cubic lattice, a first for water ice. Named ice XVIII. |
| 2018 | Millot et al. | Laser shock waves | What National Geographic called the first evidence for superionic ice: the ice briefly became hundreds of times more electrically conductive than it had previously been, a strong hint that it had gone superionic . |
The hcp phase dominates at the same 200+ GPa where UNLV found Tilt, and the CEA preprint says it is recovered at 300 K
there. How Tilt’s structure and Split’s layers fit together isn’t settled in any source here.
Much higher still, above about 1.6 TPa (1,600 GPa), one simulation study predicts a different superionic phase in which the hydrogen moves as a quasi-two-dimensional liquid
.
The honest sliver
- Is hcp really superionic? Physics World counts it as the third superionic phase. The team’s first preprint listed it as an
open question
. Their August 2026 version (arXiv v3; the published Physical Review Letters paper is not held here) says the hcp phase becomes dominant upon entering the superionic regime, as evidenced by anomalous thermal expansion
. Weck still wants more direct experimental signatures of superionic behaviour, beyond the thermal expansion we observed
.
- The boundaries are still being drawn. The CEA team’s next steps are to map where each phase is stable and where molecular ice turns superionic.
- The first sightings were fleeting. The 2018 evidence and the 2019 structure both came from shock-wave ice that lasted a few billionths of a second. Of the 2019 result, an outside physicist said more work would be needed to definitively prove the ice was superionic.
- The croissant is an analogy. Butter isn’t hydrogen ions. What carries over is the structure: a frame that holds while something mobile moves through it.
- The pecking order follows the real record. Split’s family turned up first: superionic ice was being reported in experiments years before 2026. Tilt’s symmetry break was reported in 2026. Big brother got here first.
Sources
- Physics World: New type of superionic water ice observed for the first time (Oct 2026)
- CEA preprint, version 1, “Observation of Hexagonal Close-Packed Water Ice at Extreme Pressures and Temperatures,” arXiv:2510.24305v1. The “is recovered at 300 K” and “open question” quotes on this page are from that version. arxiv.org
- Physics World: Superionic ice phases could explain unusual magnetic fields around Uranus and Neptune (2021)
- CEA preprint, version 3 (Aug 26, 2026), “Observation of hexagonal close-packed water ice at conditions in ice giant planetary interiors,” arXiv:2510.24305v3. Journal version: Phys. Rev. Lett. 137, 114101 (2026), not held here. arxiv.org
- Andriambariarijaona et al., “Observation of a mixed close-packed structure in superionic water,” Nature Communications 17:374 (2026), open access. doi.org/10.1038/s41467-025-67063-2
- Prakapenka, Holtgrewe, Lobanov & Goncharov, Nature Physics, 2021. nature.com
- Millot, Coppari et al., Nature, 2019. nature.com
- National Geographic: Bizarre form of hot ice seen on Earth (2019)
- Sun, Clark, Torquato & Car, “The phase diagram of high-pressure superionic ice,” Nature Communications, 2015
“Hold the frame. Let the rest run.”