  Certain non-Hermitian systems exhibit the skin effect, whereby the
wavefunctions become exponentially localized at one edge of the system. Such
exponential amplification of wavefunction has received significant attention
due to its potential applications in e.g., classical and quantum sensing.
However, the opposite edge of the system, featured by the exponentially
suppressed wavefunctions, remains largely unexplored. Leveraging this
phenomenon, we introduce a non-Hermitian cooling mechanism, which is
fundamentally distinct from traditional refrigeration or laser cooling
techniques. Notably, non-Hermiticity will not amplify thermal excitations, but
rather redistribute them. Hence, thermal excitations can be cooled down at one
edge of the system, and the cooling effect can be exponentially enhanced by the
number of auxiliary modes, albeit with a lower bound that depends on the
dissipative interaction with the environment. Non-Hermitian cooling does not
rely on intricate properties such as exceptional points or non-trivial
topology, and it can apply to a wide range of Bosonic modes such as photons,
phonons, magnons, etc.
