In situ carrier tuning in high temperature superconductor <span class="InlineEquation" id="IEq1">\(\hbox {Bi}_2\hbox {Sr}_2\hbox {CaCu}_2\hbox {O}_{8+{\delta} }\)</span> by potassium deposition
Abstract
We report a successful tuning of the hole doping level over a wide range in high temperature superconductor <span class="InlineEquation" id="IEq3">\(\hbox {Bi}_2\hbox {Sr}_2\hbox {CaCu}_2\hbox {O}_{8+\delta }\)</span> (Bi2212) through successive in situ potassium (K) deposition. By taking high resolution angle-resolved photoemission measurements on the Fermi surface and band structure of an overdoped Bi2212 (<span class="InlineEquation" id="IEq4">\(T_\mathrm{c}=76\)</span> K) at different stages of K deposition, we found that the area of the hole-like Fermi surface around the Brillouin zone corner (<span class="InlineEquation" id="IEq5">\(\pi \)</span>,<span class="InlineEquation" id="IEq6">\(\pi \)</span>) shrinks with increasing K deposition. This indicates a continuous hole concentration change from initial <span class="InlineEquation" id="IEq7">\(\sim \)</span>0.26 to eventual 0.09 after extensive K deposition, a net doping level change of 0.17 that makes it possible to bring Bi2212 from being originally overdoped, to optimally-doped, and eventually becoming heavily underdoped. The electronic behaviors with K deposition are consistent with those of Bi2212 samples with different hole doping levels. These results demonstrate that K deposition is an effective way of in situ controlling the hole concentration in Bi2212. This work opens a good way of studying the doping evolution of electronic structure and establishing the electronic phase diagram in Bi2212 that can be extended to other cuprate superconductors.
