Helium, in its standard form, exists as a gas at atmospheric pressure and temperatures above its critical point. However, at extremely low temperatures close to absolute zero, helium can undergo a phase transition and become a liquid.
To answer your question, it is not possible to solidify helium by compressing it at extreme pressures and freezing it at −273.15 degrees Celsius (which is absolute zero, the lowest possible temperature). This is because helium remains in its gaseous state even under extreme pressures and temperatures.
Helium has unique properties that make it resistant to solidification. It is known as a "quantum fluid" due to its behavior at low temperatures, exhibiting unusual properties governed by quantum mechanics. The combination of weak interatomic forces and the effects of quantum statistics prevents helium from solidifying under normal conditions.
However, at extremely high pressures, above several hundred thousand atmospheres, helium can solidify into a crystalline form called helium-II or superfluid helium. This occurs at temperatures below 2.17 Kelvin (−270.98 degrees Celsius), which is close to absolute zero. In this state, helium exhibits remarkable properties such as zero viscosity and the ability to flow without friction.
In summary, while helium cannot be solidified by compressing it at extreme pressures and freezing it at −273.15 degrees Celsius, it can undergo a phase transition to become a liquid at extremely low temperatures near absolute zero. Solid helium, known as helium-II, can only be achieved at very high pressures and ultra-low temperatures.