Maybe I'm wrong about it but I wanted to know whether the concept of absolute temperature is real or not.
As every element behaves differently at a particular temperatures how could we assign a common temperature to all these elements where they possess zero point energy? If they will do so then what will happen if we find an new element which ground state energy is at $\mathrm{-10\ K}$ theoretically?
The concept of absolute temperature is real. Temperature can be thought of as thee measure of the concentration of heat energy in a substance and isn't effected by different elements or compounds. Absolute temperature which is −273.15 degrees Celsius (0 kelvin) is the temperature where there is no heat energy in the substance at all. That means that all the molecules are existing in their lowest possible energy state. So conventionally is thought that it is impossible to get lower than absolute zero as to reduce the temperature, you have to remove heat energy but you can't remove heat energy in a substance which doesn't have any heat energy in the first place.
However theoretically, the Boltzmann equation does allow for substance to go minus Kelvin and in fact it actually lies above infinity Kelvin. Recently there have been several claims that this has been achieved. If you search this up on Google I am sure that you will be able to find more information on this.
