In 1912, he sought consolation in research. With great ambition and hard work, that same year he succeeded in entering the electricity subdivision in the science department of the PTR, where, at the request of its president, Emil Warburg, he introduced the liquefaction of hydrogen. In the same year he put into operation a Nernst-type liquefaction apparatus manufactured by the Hoenow Company in Berlin. His first works were based on the study of the optical characteristics of liquid hydrogen and the measurements of the electrical and thermal conductivity of copper at temperatures between 20 and 375K. 

In 1921 at the PTR he continued his low-temperature studies with the measurement of the thermal and electrical conductivity of metals such as lithium. In collaboration with the Linde Company (Munich) and with the support of the Emergency Association of German Science, he prepared the installation of helium liquefaction equipment in accordance with the Leiden method using precooled hydrogen. On 7 March 1925 Meissner succeeded in liquefying about 200 cc of helium that he had separated from a heliumneon mixture produced by Linde. Thus, besides the laboratories in Leiden (Kamerlingh Onnes, since 1908) and Toronto (John C. McLennan, since 1923), there was now a third laboratory where temperatures as low as about 1.5K were available for experiments. Meissner wanted to find out whether all metals could become superconductive simply by being at a low enough temperature and in a pure enough state. He studied monocrystalline filaments of gold, zinc, and cadmium, as well as polycrystalline iron, platinum, nickel, silver, and cadmium. Neither a high degree of purity nor the most uniform crystal structure led to superconductivity at temperatures as low as 1.3K.

According to the plans of the Ministry of the Interior and the Emergency Association of German Science, a large cryogenics institute was to be built in Germany in the mid 1920’s; the nation’s major centers for physics. Berllin and Göttingen, were being discussed as possible sites. Finally Berlin was chosen, not only because Meissner had already built a hydrogen liquefaction unit at the PTR and was just about to install a helium liquefier there, but also because of Max Planck’s influence. In 1927 the new cryogenics laboratory, which was directly under the control of the president of the PTR, was inaugurated. The possibility of numerous openings for guest researchers was welcomed by scientists at the university and in industry alike.

In the new cryogenics laboratory Meissner and his colleagues studied a great number of elements for superconductivity; in 1928 they discovered the sixth superconductive element known at that time: tantalum, used in the filaments of incandescent light bulbs. It was the first superconducting element in group V of the periodic system. Further elements that Meissner discovered to be superconductive were thorium, titanium, and vanadium. Copper sulfate was also found to lose its resistance at low enough temperatures. It was the first time that a chemical compound had become superconductive: moreover, one of its  components was an insulator. This result led to systematic studies on further compounds and alloys, among which carbides, especially niobium carbide, displayed superconductive properties even at about 10K—that is, at a temperature scientists had already been able to achieve using solid-state hydrogen.

Meissner conducted further experiments to shed light on the nature of superconductivity, studying currents in superconductive metals. On this subject, which to him was closely related to the magnetic behavior of superconductors, he remained in close contact with Max von Laue, who had been a the-oretical physicist at the PTR since 1925 and was available to experimenters for consultation half a day per week, In order to answer the question discussed by many physicists—whether a current in a superconductor fills the entire cross section or flows on the surface—Laue suggested that the magnetic field be studied between two superconductors placed very close to each other, both with a current running running through. In the spring of 1933, in the course of these measurements Meissner and his colleague Robert Ochsenfeld observed a new phenomenon that contributed greatly to the understanding of superconductivity. The magnitude of the magnetic field measured between conductors was a function of the direction of the current, which could be explained by the role played by the earth’s magnetic field. Therefore, Meissner and Ochsenfeld carried out the measurements of changes in the magnetic field close to the conductors when these were subject only to the earth’s field, that is, without any current running through them. Before superconductivity set in, the magnetic lines of force penetrated the crystals with almost no resistance because of their low susceptibility. From what was known about superconductivity at that time, it was expected that the distribution of the lines of force would remain unchanged if the temperature were lowered below the threshold level. However, Meissner and Ochsenfeld observed an increase in the lines of force in close proximity to the superconductors. Meissner interpreted this result as follows: the magnetic field flux was displaced from the crystals when superconductivity set in (see Figure 1). The magnetic field flux that previously flowed inside the conductors was now flowing between the crystals.

The Meissner-Ochsenfeld effect showed that, contrary to previous assumptions, the transition from the state of normal conductivity to that of superconductivity was completely reversible. As long as only ideal conductivity was considered to be the characteristic feature of superconductivity, according to Maxwell’s theory the state of a superconductive sample should depend on its prior state. When a sample was first made superconductive by cooling and then an outside magnetic field was applied, the sample should remain without a field, since ideal conductivity should prevent the entry of a field. In the reverse case, when the cooling followed the application of a magnetic field, a magnetic field should remain, as if frozen, inside the superconductor, even after the removal of the field. Meissner and Ochsenfeld proved that the sample in the latter case also lost its inner field through the displacement of the lines of force, which meant that the final state was independent of the means by which it was attained. This finding immediately led to the development of thermodynamic theories on superconductivity and became the starting point for Fritz and Heinz London’s phenomenological theory of superconductivity.