Electronic structure reconstruction for <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mrow> <mml:msqrt> <mml:mn>3</mml:mn> </mml:msqrt> <mml:mo>×</mml:mo> <mml:msqrt> <mml:mn>3</mml:mn> </mml:msqrt> </mml:mrow> </mml:math> charge den

Scanning photoemission microscopy (SPEM) and angle-resolved photoemission spectroscopy (ARPES) are used to investigate the electronic structure of <a:math xmlns:a="http://www.w3.org/1998/Math/MathML"> <a:mrow> <a:msub> <a:mi>Cu</a:mi> <a:mrow> <a:mn>0.33</a:mn> </a:mrow> </a:msub> <a:msub> <a:mi>TiSe</a:mi> <a:mn>2</a:mn> </a:msub> </a:mrow> </a:math> across the charge density wave (CDW) transition. The electronic structure is found to be largely homogeneous in the normal state above the CDW transition. The ARPES measurements using a submicron beam size reveal a large electronlike pocket due to the Ti band at the <b:math xmlns:b="http://www.w3.org/1998/Math/MathML"> <b:mrow> <b:mi>M</b:mi> </b:mrow> </b:math> point while the Se <c:math xmlns:c="http://www.w3.org/1998/Math/MathML"> <c:mn>4</c:mn> <c:mi>p</c:mi> </c:math> band at the <d:math xmlns:d="http://www.w3.org/1998/Math/MathML"> <d:mi mathvariant="normal">Γ</d:mi> </d:math> point is absent due to electron doping by the intercalated Cu. We have observed <f:math xmlns:f="http://www.w3.org/1998/Math/MathML"> <f:mrow> <f:msqrt> <f:mn>3</f:mn> </f:msqrt> <f:mo>×</f:mo> <f:msqrt> <f:mn>3</f:mn> </f:msqrt> </f:mrow> </f:math> Fermi surface reconstruction below the CDW transition, in which Ti <g:math xmlns:g="http://www.w3.org/1998/Math/MathML"> <g:mn>3</g:mn> <g:mi>d</g:mi> </g:math> bands are folded into a reconstructed BZ rotated by <h:math xmlns:h="http://www.w3.org/1998/Math/MathML"> <h:msup> <h:mn>30</h:mn> <h:mo>∘</h:mo> </h:msup> </h:math> , making the <i:math xmlns:i="http://www.w3.org/1998/Math/MathML"> <i:mi mathvariant="normal">Γ</i:mi> </i:math> and <k:math xmlns:k="http://www.w3.org/1998/Math/MathML"> <k:mi>K</k:mi> </k:math> points equivalent. The results demonstrate the presence of a <l:math xmlns:l="http://www.w3.org/1998/Math/MathML"> <l:mrow> <l:msqrt> <l:mn>3</l:mn> </l:msqrt> <l:mo>×</l:mo> <l:msqrt> <l:mn>3</l:mn> </l:msqrt> </l:mrow> </l:math> CDW phase in the electronic structure of heavily Cu-intercalated <m:math xmlns:m="http://www.w3.org/1998/Math/MathML"> <m:mrow> <m:msub> <m:mi>Cu</m:mi> <m:mrow> <m:mn>0.33</m:mn> </m:mrow> </m:msub> <m:msub> <m:mi>TiSe</m:mi> <m:mn>2</m:mn> </m:msub> </m:mrow> </m:math> . The findings reveal a platform for investigating the two-dimensional electronic phase in 1T- <n:math xmlns:n="http://www.w3.org/1998/Math/MathML"> <n:msub> <n:mi>TiSe</n:mi> <n:mn>2</n:mn> </n:msub> </n:math> chalcogenides, which exhibit a unique interplay between CDW, superconductivity, and excitonic/lattice instabilities.